# Replacing the inboard with an outboard motor - advice please!!!



## jaysonak (Nov 21, 2020)

Hello, 

Full disclosure, I'm totally new to sailing. In fact, I've only been once. Long story short, I now have a old Cascade 29 that has been out of the water for 15 years. My question for you all (who know way more than me), is what's your thoughts on removing the inboard motor (Yanmar 2QM15 - a two cylinder 15 hp engine) and putting an outboard motor on the back? I believe I would have to put the outboard on an articulating bracket, and even when it was lowered into the water the handle might make contact with the aft of the boat? I'm not sure if there's a way to choose to mount a throddle control somewhere else? I'm also not sure how time intensive it would be for me to 'plug the hole' left by the prop shaft after removing the engine. 
I'm considering it because it would give me more room for storage, and would be easier to access for maintenance in the long run (I believe). What's your guy's thoughts? Thank you!

-Jayson


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## JimsCAL (May 23, 2007)

A 29 is a bit big for an outboard. What's wrong with the Yanmar?


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## jaysonak (Nov 21, 2020)

JimsCAL said:


> A 29 is a bit big for an outboard. What's wrong with the Yanmar?


JimsCAL thank you for responding! I haven't fired it up yet to '_discover'_ what's wrong with it - or if there's anything wrong with it at all. But I wouldn't know how to test it while it's out of the water in the first place. Maintenance goes about $120/hour where I live. So instead of potentially sinking money into an old engine, I am considering just getting a new motor, and the thought of an outboard would provide more space for storage. I also thought that having a prop out of the water (with the motor on an articulating arm) would provide less drag. But this is just theory - like I said, very new to all of this.


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## capttb (Dec 13, 2003)

jaysonak said:


> My question for you all (who know way more than me), is what's your thoughts on removing the inboard motor (Yanmar 2QM15 - a two cylinder 15 hp engine) and putting an outboard motor on the back?


Not generally a good idea, but it's been done.


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## jaysonak (Nov 21, 2020)

Capttb thank you for your input! Would you mind educating me a little bit and expanding on why you say that?


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## paulk (Jun 2, 2000)

How old is the boat? Diesels routinely last a LONG time. Ours is from 1982. People avoid putting outboards on the backs of sailboats for a number of reasons. One, as you've already suggested, is that reaching the controls on the motor's tiller becomes a problem. Another is that having all that weight so far aft messes up the balance of the boat and makes it hard to sail. A third is that gasoline can be dangerous on a boat. Fumes sink into the bilge and can explode - along with the boat. Finally, despite the weight of the motor making the stern sink deeper, pitching in waves can cause the propeller to lift out of the water, causing the motor to race (bad for the motor) and not providing propulsion (bad for getting ahead). Sailboats with outboards are usually small and light or are designed purposely to use them. An example would be a J/24. They weigh about half as much as your boat does, so are easier to push around with an outboard. J/24's are also used almost exclusively for racing, and the motors are unmounted and stored below once the boats arrive at the starting area. Flying Tiger 10M's are bigger than your Cascade, but still much lighter by about a ton and a half. The outboard that powers them fits into a well so the propeller stays in the water. According to Sailboatdata, Cascade 29s were first built in 1961, and came with Atomic 4 gasoline engines. The Yanmar 2QM15 was built from 1977-80. If yours hasn't been used for 15 years, it is "newer" than ours; at least less used. Even though it may not be easy to access, diesels typically need less maintenance than gasoline engines. Spending several thousand dollars for an outboard ($3000 for a 15hp Honda) that may not push the boat well, especially in rough conditions when you NEED it to, does not seem like a good investment when you have an engine that was designed to work already in the boat and you haven't even tried to start it.


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## jaysonak (Nov 21, 2020)

paulk said:


> How old is the boat? Diesels routinely last a LONG time. Ours is from 1982. People avoid putting outboards on the backs of sailboats for a number of reasons. One, as you've already suggested, is that reaching the controls on the motor's tiller becomes a problem. Another is that having all that weight so far aft messes up the balance of the boat and makes it hard to sail. A third is that gasoline can be dangerous on a boat. Fumes sink into the bilge and can explode - along with the boat. Finally, despite the weight of the motor making the stern sink deeper, pitching in waves can cause the propeller to lift out of the water, causing the motor to race (bad for the motor) and not providing propulsion (bad for getting ahead). Sailboats with outboards are usually small and light or are designed purposely to use them. An example would be a J/24. They weigh about half as much as your boat does, so are easier to push around with an outboard. J/24's are also used almost exclusively for racing, and the motors are unmounted and stored below once the boats arrive at the starting area. Flying Tiger 10M's are bigger than your Cascade, but still much lighter by about a ton and a half. The outboard that powers them fits into a well so the propeller stays in the water. According to Sailboatdata, Cascade 29s were first built in 1961, and came with Atomic 4 gasoline engines. The Yanmar 2QM15 was built from 1977-80. If yours hasn't been used for 15 years, it is "newer" than ours; at least less used. Even though it may not be easy to access, diesels typically need less maintenance than gasoline engines. Spending several thousand dollars for an outboard ($3000 for a 15hp Honda) that may not push the boat well, especially in rough conditions when you NEED it to, does not seem like a good investment when you have an engine that was designed to work already in the boat and you haven't even tried to start it.


Wow - Thank you for that 😅! You are right, I haven't tried to start it yet - just forecasting different cost options. I also assumed the motor was as old as the boat. To answer your question, the boat was built in 1963 and I'd thought the motor was just as old. Knowing now that the motor is considerably newer puts my mind at great ease.
These are all wonderful learning points that I'm very grateful for. Looking around, I was having a hard time finding sailboats that had done was I was considering - now I know why! Thank you so much Paulk, you obviously put some research in and answered my question very extensively - much appreciated!


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## Keyframe42 (Aug 24, 2020)

Hey man, I don't have much more experience than you, but i will point out that a good outboard is expensive, maybe if you get an estimate it would be cheaper... plus you can't just pull the motor, where the shaft emerges from the hull will need to be dealt with, so estimate that into the cost of a new outboard. I am sure that the guys on here will tell you how easy it really is, but as one beginner to another, messing with a hole in the bottom of your boat would not be one of my first projects.


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## capttb (Dec 13, 2003)

Shifting motor weight from low and centered to high and behind transom (and off center).
Outboards come out of water in large seas.
Cost of outboard, mount, remote controls and fuel system can be more than fixing existing engine.
Outboard alternators are very small.
Gasoline more hazardous than diesel.


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## jaysonak (Nov 21, 2020)

Keyframe42 said:


> Hey man, I don't have much more experience than you, but i will point out that a good outboard is expensive, maybe if you get an estimate it would be cheaper... plus you can't just pull the motor, where the shaft emerges from the hull will need to be dealt with, so estimate that into the cost of a new outboard. I am sure that the guys on here will tell you how easy it really is, but as one beginner to another, messing with a hole in the bottom of your boat would not be one of my first projects.


Keyframe42,

From one beginner to another... I appreciate your level headed answer (I'm off in the clouds)! That hole in the bottom... yeah... I kept telling myself it probably wouldn't be a huge deal (basing off of YouTube videos I've watched), but I can totally see myself not realizing how much of a hassle I will create for myself by removing what's already there. I appreciate you man, and hope you find your first boat soon!

-Jayson


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## jaysonak (Nov 21, 2020)

capttb said:


> Shifting motor weight from low and centered to high and behind transom (and off center).
> Outboards come out of water in large seas.
> Cost of outboard, mount, remote controls and fuel system can be more than fixing existing engine.
> Outboard alternators are very small.
> Gasoline more hazardous than diesel.


TB,

Thank you for your reply - it seems that pretty much everyone thinks this isn't a great idea. Thank you for taking the time and sending me your thoughts and experience - so appreciated!!!


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## tempest (Feb 12, 2007)

Well, 1st you need to determine if it works. Was it properly stored? Oi changel, filter, rust inhibitor, cooling system flushed? 

Try to wake it up from it's long slumber. Then, if it works, my philosophy is: "If it ain't broke don't fix it" It may last longer than you or I. 

+ all the other reasons mentioned, like weight aft, gasoline explosiveness, etc. etc. adding an outboard to the stern, and then filling the old engine compartment with Stuff. Not a good idea. IMHO. and it might cost more $$ than you're trying to save.


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## arf145 (Jul 25, 2007)

Yeah, keep the diesel if at all possible. The first things that I would do (which can be done by virtually anyone) would be to drain the oil (you'll want a vacuum oil extractor) to take a look at it, and then put in fresh oil and filter (not a big investment) and then see if it turns over by hand. Some might say you can check to see if it turns over without even an oil change. There's probably a big nut on the front of the engine that you can get a wrench on to turn it.


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## 508422 (Aug 26, 2018)

jaysonak said:


> Hello,
> 
> Full disclosure, I'm totally new to sailing. In fact, I've only been once. Long story short, I now have a old Cascade 29 that has been out of the water for 15 years. My question for you all (who know way more than me), is what's your thoughts on removing the inboard motor (Yanmar 2QM15 - a two cylinder 15 hp engine) and putting an outboard motor on the back? I believe I would have to put the outboard on an articulating bracket, and even when it was lowered into the water the handle might make contact with the aft of the boat? I'm not sure if there's a way to choose to mount a throddle control somewhere else? I'm also not sure how time intensive it would be for me to 'plug the hole' left by the prop shaft after removing the engine.
> I'm considering it because it would give me more room for storage, and would be easier to access for maintenance in the long run (I believe). What's your guy's thoughts? Thank you!
> ...


Take a look at Atom Voyages, google it. There is a wealth of information on it. To be done right by someone else you could probably rebuild the diesel cheaper. To go electric you could probable rebuild the diesel cheaper. The out board needs to be low enough in the water to keep it in the water when waves are picking up the back of the boat. So the motor on a larger boat would be very low. Getting water baths. Probable be cheaper to buy a smaller boat, 22 or so that is made for the outboard. Probably cheaper in the long run. My opinion is based on someone else, at $120 dollars an hour doing the work. There was quite recently a very very long discussion on inboard to outboard conversion. Dennis


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## Minnewaska (Feb 21, 2010)

I won't repeat the good warnings about making the switch. I will add that it could be difficult to sell a boat that is expected to have an inboard motor, if the inexperienced owner made such a major engineering change.


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## JimsCAL (May 23, 2007)

You said you didn't know how to test run the diesel out of the water. Done all the time to winterize engines. Need a fully charged battery obviously. Cooling water will come from a bucket that the engine inlet water hose is put in with the bucket kept full with a garden hose.

With an engine unused for that long, other things need to be done. Change oil and filter, get rid of old fuel and put in fresh, roll engine by hand before turning the key, etc.


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## cdy (Nov 10, 2013)

Not sure on the boat you are looking at - I had an outboard on the back of a Pearson 30 - it worked OK - but the Pearson is a good sailing fairly light 30 ( late 70's) - the outboard was for getting in and out of slip - after that its quickly to sailing - if the boat is heavier and not as responsive under sail - then probably not a good idea - there is a guy sailing around the world on a heavy 30 foot cutter rigged with only a sculling oar - so it can be done - but you need patience and timing ( and experience helps a lot)


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## Arcb (Aug 13, 2016)

I wouldn't trade out a working diesel for an outboard for all the reasons listed above.

However, if the inboard is truly shot I have known a few that have done it with some success. There are a few issues even if done well. 

Cavitation. An outboard on the back of a big boat will lift out of the water, make noise and do a poor job of propelling the boat. 

Maneuvering. Maneuvering with an outboard on the transom can be a real pain. No way to direct thrust over the rudder. What this means is the bost needs speed through the water to steer. Not always practical maneuvering in tight spots.

No decent way to reach the engine. When you have outboards on small sailboats, to improve maneuvering you can turn the outboard itself to vector thrust. On a big boat you can't reach the controls or vector thrust. See above.

Once over about ~20 ft the best designed outboard set ups are usually a well in the cockpit where the propeller is far enough forward it doesn't cavitate, controls are easily reached from the cockpit and the propellers wash is directed over the rudder, just like an inboard set up.

The boats where I have seen it done successfully were boats that sailed well and only relied on their outboards very occasionally. Generally, these are people who would be comfortable sailing their boat in and out of dock and on and off anchor with the help of no outboard at all and the outboard is really for those glass calm conditions when there isn't enough wind to sail.


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## Jeff_H (Feb 26, 2000)

So now that you have apparently been convinced that keeping the Yanmar diesel makes a lot more sense than trying to put an outboard on the boat, we should talk about what you need to do before you try to start the engine. 
I will note that Yanmar engines tend to be very reliable, and the parts are pretty affordable and available. I will also note that is roughly the same age as my Yanmar. 

But if the engine has been sitting there are some things you will want to do before you start the engine for the first time. 
If it was me, I would:
-grab the flywheel (pulley) and try to rotate the engine a few degrees to make sure that it isn't seized. Assuming it moves.....
-replace the raw water pump impeller and it's gasket.
-pump out all of the fuel in the tank, clean the tank as best I could, and add new fuel.
-check all hoses
-check the belt tension and plan to replace all the belts once you determine that the engine runs.
-replace the lube oil with the engine cold(I know that is not as easy and generally not the way to do it , but you will do it right once you determine that the engine runs.)
- make sure that there is water in the fresh water cooling system. 
-Fully charge the battery
At that point I would close the raw water intake seacock and try to start the motor. As soon as it fires up, let it run no more than a few seconds and shut it down, or else quickly open the raw water intake seacock. Once the seacock is open watch to make sure that water is coming out with the exhaust. 
With the engine running, look for signs of leaks (oil, water or fuel) 
If you don't see leaks, run the engine for 15 20 minutes then shut it down. 
Replace the lube oil again this time replacing it's filter. Replace the belts, replace the transmission fluid. Replace the fuel filters, Replace any suspect hoses. Test the transmission and then use your boat.
Jeff

-


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## Rockter (Sep 11, 2006)

Rock it to free the crank. Disconnect the feed to the water pump and stick the end of the hose in to a bucket of water. Do not use a water hose directly to the pump. Connect a battery and start the motor. Take it from there.


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## Jeff_H (Feb 26, 2000)

Rockter said:


> Rock it to free the crank. Disconnect the feed to the water pump and stick the end of the hose in to a bucket of water. Do not use a water hose directly to the pump. Connect a battery and start the motor. Take it from there.


There are a slew of risks to doing what you suggest on an engine that has been sitting for 15 years. 
First of all the fuel in the tank is stale and bound to be contaminated. Without changing the fuel before trying to start the engine, there is a risk of damaging the injectors.
Since this engine has sat for 15 years, it would take a lot of cranking to get it to start. Cranking the engine with the raw water intake open or sitting in a bucket of water, risks hydrolock, and thereby damaging connecting rods, valves or worse.
Cranking the engine without replacing the raw water impeller risks the impeller shredding and clogging the heat exchanger. 
Running the engine without changing the oil threatens to pump water and gunk into oil passages and damaging bearings, seals and journals.
I still suggest that it pays to take a more conservative approach to starting an engine that has not been started for this long.

Jeff


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## SHNOOL (Jun 7, 2007)

I agree with these guys, its worth the effort to see if you can get the old oil burner working.
Outboard on a 29 footer, would not be a lot of fun.


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## PhilCarlson (Dec 14, 2013)

@jaysonak Glad you asked the question and +1 to all the good advice. I will add that considering the cost of a good outboard plus the all the other stuff needed for installation and operation, vs the cost of rebuilding the Yanmar (pretty extreme case) you would probably come out ahead. Way ahead of you do the work yourself.

My boat had been on the hard for 10 years when I picked her up. The owner said he ran the Yanmar 2GM20(f) regularly to keep it in shape, but who really knows. He did fire it up for me. I had to replace all of the 'regular maintenance' parts but 6 going on 7 years later I've never had a problem.

You can download the service manual here: YANMAR 2QM15 SERVICE MANUAL Pdf Download | ManualsLib
Parts manual: https://www.lsm-diesel.dk/2012/yanmar/pdf/motordele_2qm15.pdf

2QM15 Maintenance discussions:








Yanmar 2QM15 Maintenance


I took my first crack at this today. As my first project, I successfully changed the oil without making too much of a mess. But I did under estimate how much spillage would come out of the oil filter, (seems like a dopey design to have it mounted horizontally rather than vertically). The oil...




www.sailnet.com












Yanmar 2QM15


Hi, Question about a 2QM15 that's for sale locally. Raw water cooled, 3500 hours on it , can be seen running and the guy's asking $600. I want to replace my inboard but my concern is availability of parts. Can a guy still get pistons, sleeves, valves , all the bits and pieces for these engines...




www.sailnet.com





Good luck!


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## Jeff_H (Feb 26, 2000)

One quick point on the oil filter change issue mentioned in the quoted post. The hot ticket on that is to cut the bottom out of a milk jug and place it in the bilge below the oil filter. Make the jug bottom as tall as will fit and as close to the engine block as you can. Most of the oil from the old filter will end up in the jug bottom. I empty the oil in the old filter into the jug bottom before transferring it to the trash to avoid drips. Using a funnel, I drain the oil from the jug bottom into the waste oil container using a funnel.


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## jaysonak (Nov 21, 2020)

Arcb said:


> I wouldn't trade out a working diesel for an outboard for all the reasons listed above.
> 
> However, if the inboard is truly shot I have known a few that have done it with some success. There are a few issues even if done well.
> 
> ...


Arcb,

Just wanted to say thank you for going out of your way and laying out all of the reasons why an inboard is a good thing. Thank you for bringing your experience!

-Jayson


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## jaysonak (Nov 21, 2020)

Jeff_H said:


> So now that you have apparently been convinced that keeping the Yanmar diesel makes a lot more sense than trying to put an outboard on the boat, we should talk about what you need to do before you try to start the engine.
> I will note that Yanmar engines tend to be very reliable, and the parts are pretty affordable and available. I will also note that is roughly the same age as my Yanmar.
> 
> But if the engine has been sitting there are some things you will want to do before you start the engine for the first time.
> ...


Jeff,

This is an amazing check list of things to do! Thank you so much for taking the time to throughly go through all these line items one by one!

-Jayson


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## jaysonak (Nov 21, 2020)

Rockter said:


> Rock it to free the crank. Disconnect the feed to the water pump and stick the end of the hose in to a bucket of water. Do not use a water hose directly to the pump. Connect a battery and start the motor. Take it from there.


Got it! Thanks Rockter!


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## jaysonak (Nov 21, 2020)

Jeff_H said:


> One quick point on the oil filter change issue mentioned in the quoted post. The hot ticket on that is to cut the bottom out of a milk jug and place it in the bilge below the oil filter. Make the jug bottom as tall as will fit and as close to the engine block as you can. Most of the oil from the old filter will end up in the jug bottom. I empty the oil in the old filter into the jug bottom before transferring it to the trash to avoid drips. Using a funnel, I drain the oil from the jug bottom into the waste oil container using a funnel.


@Jeff_H thank you again for coming back and continuing with all the advice. I'm writing them down and taking it all it - thank you!!


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## jaysonak (Nov 21, 2020)

PhilCarlson said:


> @jaysonak Glad you asked the question and +1 to all the good advice. I will add that considering the cost of a good outboard plus the all the other stuff needed for installation and operation, vs the cost of rebuilding the Yanmar (pretty extreme case) you would probably come out ahead. Way ahead of you do the work yourself.
> 
> My boat had been on the hard for 10 years when I picked her up. The owner said he ran the Yanmar 2GM20(f) regularly to keep it in shape, but who really knows. He did fire it up for me. I had to replace all of the 'regular maintenance' parts but 6 going on 7 years later I've never had a problem.
> 
> ...


@PhilCarlson THANK YOU SO MUCH for including these manuals!!!! How awesome is the sailing community!


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## roverhi (Dec 19, 2013)

The 2QM probably has a hand crank and compression release levers. That will make testing it easier as you can turn it over with the hand crank with the compression releases activated. The releases will be levers on the head, one for each cylinder. After changing the oil and filters try and get the engine to turn over. For very short time you can crank it with the starter and even run the engine. When I say short mean a minute or two at a time. Running the engine without cooling water will eventually ruin the water pump impeller if you do it too long. Probably would change the impellor in any case before trying to start the engine. Trying to start the engine with cooling water is also time sensitive. Cranking the engine will pump water through the system and build up in the muffler if the engine doesn't start. Probably best to try and start the engine without water and shut down immediately if it fires then hook up the cooling water. 

Is the engine coolant cooled with a heat exchanger or raw water??


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