# Yanmar single-cylinder engine



## VF84Sluggo (Jan 1, 2015)

There's a really nice 1982 Cherubini Hunter 27 in my area for sale. The boat has been well cared for. It has a single-cylinder 9.5hp Yanmar diesel. Any thoughts on this engine? Reliability? Things to watch for? Etc......

Once again, a newb looking for info. I've tried 'googling', forum searches, etc., but couldn't find anything (yes, probably due to my search skills, or lack thereof! )

Thanks in advance!


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## celenoglu (Dec 13, 2008)

Single cylinder Yanmar is as good as 2-4 cylinder Yanmars. In my opinion Yanmar is the best marine engine. Age and engine hours is of course critical. Age destroys the non metalic parts of the engine causing water and oil losses.


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## VF84Sluggo (Jan 1, 2015)

The owner says it was overhauled in 1999. He's not sure of the hours on the engine. So, I have to consider the cost of overhauling again an old engine, not sure how much that might run.


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## sony2000 (Jan 30, 2013)

The biggest complaint is that the boats are too large for them. You won't make hull speed. If you battle currents you may regret your decision.


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## VF84Sluggo (Jan 1, 2015)

Yep, 9.5 hp seems weak to me, too, for this boat. Currents where I live can be an issue, especially if near a pass as the tide is moving.

Sure wish she had a stronger motor. Otherwise, the boat is nice.


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## celenoglu (Dec 13, 2008)

A 27 ft boat should reach hull speed with a single cylinder Yanmar if the propellor is correct. Hull speed is a critical value. To overcome this speed you need an engine twice or thrice the power. Since hull speed is the speed on the water, engine power might not be a solution.


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## VF84Sluggo (Jan 1, 2015)

Sure, that makes sense. Just wondering, as Sony suggested, if 9.5hp is up to the task of even getting close to hull speed. Not sure what that is on a Hunter 27.


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## aa3jy (Jul 23, 2006)

A marine survey with a sea trial should be highly advised if your really serious in the vessel...


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## aloof (Dec 21, 2014)

Attaining hull speed with the auxiliary engine is not a rule. The money and weight inherent in a large engine can be put to much better use.

I suppose the exception would be if your home berth is on a river. Then it is not hull speed you are seeking. What you want is several knots greater than the current.


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## Barquito (Dec 5, 2007)

In calm conditions, you should be able to reach hull speed. However, if there is a headwind or choppy conditions, you may not be able to go that fast. It wouldn't be a show-stopper for me.


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## bljones (Oct 13, 2008)

Yes, that Yanmar is enough to power that boat..... but not enough to reach hull speed. It WILL power it to 85% of hull speed, and that's not horrible. Most sailboats between 25- 30 feet are theoretically underpowered, but still viable. So, should it be a deal breaker? nah. They are a dead simple engine, simpler even than a lawn mower engine. The only minor downside to a yanmar engine is the lack of glow plug for cold starting, although, unless the water and air are near freezing, the engine should start.

Regarding hull speed and the power required...
the waterline of the Hunter 27 in question is 22 feet, the displacement is 7000 lbs. Plug that data into here: Boat Speed Calculator
and see what you get.


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## Frogwatch (Jan 22, 2011)

I'd say this is a very good engine for this boat. My 28' S2 originally had a 1 cylinder Yanmar with only 6.5 hp and I cruised it all over the Gulf of Mexico in FL.
It routinely achieved 5 kts with a 3 blade prop and clean hull in light chop and slowed to about 4 in moderate chop.
The newer 1 cylinder Yanmar the 1GM10 this poster describes is much better for this smaller boat and I think should get near 6 kts in calm water with the right prop.
It is a wonderful little engine that is amazingly reliable. If it is older, you may have to replace the mixing elbow or at least clean it out.
Once you get the boat, I recc'd you get in touch with PerfectPitch props and get their prop for it. These are massive oversize hard plastic props. They will give you the right diameter for your boat and if necessary for even more power from the prop sell a shaft extension so you can use a larger prop. This enables you to get as much thrust out of a 2 blade as from a 3 blade.
I eventually replaced my old 1GM (6.5 hp) with a 2GM13 because I wanted to do extensive cruising and I knew a lot of it would be under power.


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## Group9 (Oct 3, 2010)

I had a one cylinder Yanmar on my Cape Dory 25D. I thought I remembered it as being rated at 7.5 HP. It was a great motor, and it easily pushed my CD to hull speed. One of the things I really liked about it was the decompression lever. You could run the batteries down to almost nothing, flip the decompression lever and get is spinning, let it off and it would crank.

It came with a hand crank, but a friend and I tried for hours to get it hand cranked in the slip one day and finally gave up. Obviously, there is some technique involved, that we couldn't master.


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## CatalinaRob (Jun 25, 2010)

most older production boats of that size are underpowered IMHO. I have an older Catalina 30 and it has a single-cylinder Yanmar w/12HP -- I had it rebuilt 12 yrs ago and it reliable as ever (knock on wood). Its underpowered though ad is an issue when I want to get in but I learned to live with it and plan my trips around the tide and prevailing currents so know in advanced.


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## Bill-Rangatira (Dec 17, 2006)

bljones said:


> Yes, that Yanmar is enough to power that boat..... but not enough to reach hull speed. It WILL power it to 85% of hull speed, and that's not horrible. Most sailboats between 25- 30 feet are theoretically underpowered, but still viable. So, should it be a deal breaker? nah. They are a dead simple engine, simpler even than a lawn mower engine. The only minor downside to a yanmar engine is the lack of glow plug for cold starting, although, unless the water and air are near freezing, the engine should start.
> 
> Regarding hull speed and the power required...
> the waterline of the Hunter 27 in question is 22 feet, the displacement is 7000 lbs. Plug that data into here: Boat Speed Calculator
> and see what you get.


 i heard someone fitted a manifold heater to one of these for cold starting


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## celenoglu (Dec 13, 2008)

I didnot hear a single story for Yanmars not starting due to cold. I used a single cylinder Yanmar for nearly two years, and it always started even in -3 C without any heating. The engine hours was somewhere 4000-4500.


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## Frogwatch (Jan 22, 2011)

Yes, that decompression lever is great for starting on either weak batteries or cold mornings. I was also never able to hand crank it.

I really think the 9.5 hp is plenty for this boat with the right prop. If he really wants to fight current, put an outboard bracket on the transom and use the dinghy motor as a helper.
I never had any problems with my old 1 GM (6.5 hp).


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## VF84Sluggo (Jan 1, 2015)

I've talked with the owner again, and he said they've never had a problem with that 9.5hp/1-cylinder motor being able to push their Hunter 27 along at a good speed. As has been suggested, the prop is probably the key.


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## bljones (Oct 13, 2008)

celenoglu said:


> I didnot hear a single story for Yanmars not starting due to cold. I used a single cylinder Yanmar for nearly two years, and it always started even in -3 C without any heating. The engine hours was somewhere 4000-4500.


I didn't say they won't start, but I know that my new-to-me YSM-8 and previous 1GM10 are dramatically slower to start when cold. Not a deal breaker, not a knock ono the engine, but one of the idiosyncracies of the engine to be aware of.


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## mf70 (Nov 6, 2014)

I've got the YSB12 in my 32' sharpie. No concern about power in 10 years. If you can get it to hand start, you can be more confident it's in good condition. Full throttle, compresion release, spin in up 3 rev's, pop release on last rev and pull through the BANG. There have been times I have been happy to have that capacity.


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## djodenda (Mar 4, 2006)

Had a 6.5 HP single cylinder Petter diesel on my old Catalina 27.. Plenty of power


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## gjaoryce (Mar 16, 2011)

I had one of the 12hp versions in my last boat. While a bit under powered it never failed me and started up every season without any coaxing. Maintenance is easy. I have a 9.5hp version that I found for free to use some of the spares if needed. One thing about them is the noise and vibration are more then you would find with a balanced engine. Definately not a show stopper if it is in good working order. Oh and one last thing it doesn't seem to both even burning fuel! On average with 50 days a year on the water I might go through 2 20l jerry cans of diesel! Can't say the same for my E42 I go through that in about 5 hours now!!


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## Bill-Rangatira (Dec 17, 2006)

Barquito said:


> In calm conditions, you should be able to reach hull speed. However, if there is a headwind or choppy conditions, you may not be able to go that fast. It wouldn't be a show-stopper for me.


i generally tend to have sails up in anything more than a light breeze 
the only time i run the engine is for anchor, docking, etc 
and if you really want to go fast then put up sail


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