# Will a 6hp outboard drive my 4000 lb boat?



## Quickstep192 (Jan 6, 2001)

My Quickstep weighs 4000 pounds. It's always had an 8 hp outboard. I'm wondering if a 6 is enough because I'd like to be able to reduce the weight in the stern and on my arms when it comes time to take it off. I've never been able to get the 8hp up to full throttle, so that has men wondering if less HP would be OK. Also, if I can get by with 6HP, do I need to have any concern that the 6's only have a single cylinder?


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## PBzeer (Nov 11, 2002)

Depends on what you expect the motor to do. Are tides or currents a factor? Heading into a stiff wind or chop? Does your bottom stay clean? 

If none of those are a factor, then a 6 should do. If they are a factor, you might, probably, will miss the extra umph from the 8.


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## Quickstep192 (Jan 6, 2001)

Good points. Yes, I would want to be able to power into a chop or headwind. 
Do you think a 6hp wouldn't be up to the task?


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## sawingknots (Feb 24, 2005)

for a short time i used a 6hp on my py26,7000 plus lbs,the 6 did ok until i had to go against a strong current or head wind,i would think the 6 might be ok for your 4000 lb boat depending on the current ,wind factor,i don't see any problem with the single cylinder.btw i replaced the 6 with a 9.9 and cut the fuel consumtion in half,i suppose because the bigger engine had to work less hard


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## Faster (Sep 13, 2005)

In most conditions a 6 hp should do what you need.. but relatively speaking you might slow a bit in a stiff headwind vs the 8 horse.

Sawingknots.. did you go 2 stroke to 2 stroke or 2 stroke to 4? That's an interesting observation.


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## JoeDiver (Feb 2, 2011)

I'm replacing my motor next month. I currently have a little Yamaha 5HP, 99 model. Normally, I only use my motor to get in/out of the marina. Soon as I clear the channel I'm under sail. I also use it to anchor or hunt a ball to tie up. It's been perfectly fine for my C25, although it is a bit underpowered and only hits 4.5 kts under full throttle. I sail on a lake so current and chop are not a factor.

I was considering a 9.9 as it's the most common motor folks with my boat move to, but I'm looking at $2500 at least with motor and new mount.

I decided to step back a little. I'm going to buy the new 2012 C model Tohatsu SaiPro. It's a little 6HP, 25" shaft, longer tiller, shifter moved to front of motor, and an alternator to charge the house. No new motor mount needed. Comes with high thrust propeller.

I think this little motor will work just perfect for me and what I need. The extra 1HP and deeper bite with high thrust propeller should motor me around 4 kts at 3/4 throttle or maybe less. Plus, I'm saving about $1k in cost, with no new mount needed.

Tohatsu SailPro


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## sea_hunter (Jul 26, 2000)

No tide, no wind, no chop, no traffic sure. Where I come from we'd put a 15-25 to do the job.


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## sawingknots (Feb 24, 2005)

Faster said:


> In most conditions a 6 hp should do what you need.. but relatively speaking you might slow a bit in a stiff headwind vs the 8 horse.
> 
> Sawingknots.. did you go 2 stroke to 2 stroke or 2 stroke to 4? That's an interesting observation.


i went to a 9.9 2 stroke,it was a desperation buy, i was far from anywhere and it was the only one available,i've since installed a inboard diesel and only use the outboard as a backup


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## lans0012 (Jul 16, 2008)

*big ear prop*

I think you should be ok with a 6 hp. I had a 6 on my 2200lb ranger 22 and it was way more power than I needed. however it's not like you are going to get it going any faster than hull speed.

Currently I've got a 7hp inboard on my CAL 27 that weighs about 6k pounds when fully loaded. I have powered into 30kt headwinds towing a dinghy with no problem to make 5kts.

They do make 25" shafts and that really helps keep the prop in when you are going against chop. I had a 6hp Nissan 1 cylinder 25" shaft that I paid about 1500 bucks brand new, and also charged the batteries.

They also make a elephant ear prop that is more appropriate for sailboats because you are only going 5-7kts anyway. The props these things come with are more setup for planing a small dinghy or skiff at higher speeds around 10kts.


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## Ulladh (Jul 12, 2007)

I have a 6hp Tohatsu on a 3,000 lb boat. At slack current on the Delaware less than 1/2 throttle will move the boat at 5+ knots, but against the current it will be 1 1/2 to 2 knots.

Add chop to current and if not enough breeze for sailing, I just have to wait for the current to change.

Select your outboard for local conditions or your tolerance for waiting.


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## Fiasco1 (Dec 4, 2010)

I ran a 5 hp Tohatsu on my Olson 30, 3600 lbs for years. Traded up to the 6 hp sail drive Tohatsu because of motors increasing age. It will have more than enough drive for 4000.lbs you may never run full throttle with it either. It also has the benefit of a charger standard to top up batteries. 55 lbs if i remember right.


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## Ulladh (Jul 12, 2007)

I have the 20" 6hp Tohatsu, bought before the 25" was available. I need an excuse to get the 25" but this motor will just not die.


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## Tbrad (Aug 15, 2011)

A larger engine will let you use a lower rpm thus less fuel. Hull speed is hull speed. Faced with a seven knot current and a hull speed of seven knots.....there you are.


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## dabnis (Jul 29, 2007)

I had a Coronado 25, about 4,500 lbs, IIRC. Had a 6HP 2 stroke which was OK for calm conditions. However in and outside of San Francisco Bay it was marginal in rough windy conditions. Went to a 15 HP 2 stroke, which was the same size and weight as the 9.9HP, and it was all the power I needed. The 9.9 probably would have been enough. On both motors I went with a prop with 1" less pitch than the stock prop and it worked well. Suggest you get the high thrust prop and the longest shaft that will fit, especially if you have a transom mounted engine.

Dabnis


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## TohatsuGuru (Oct 3, 2007)

The short answer is definitely not. The long answer is that if you have low expectations, never go against a current, never go into a stiff breeze, put the lowest pitch prop on it that you can find and don't mind the vibration that you get from any single cylinder engine...You might be happy 50% of the time. IE The 500 lb per hp rule is commonly used for a reason.


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## steel (Sep 1, 2010)

sawingknots said:


> for a short time i used a 6hp on my py26,7000 plus lbs,the 6 did ok until i had to go against a strong current or head wind,i would think the 6 might be ok for your 4000 lb boat depending on the current ,wind factor,i don't see any problem with the single cylinder.btw i replaced the 6 with a 9.9 and cut the fuel consumtion in half,i suppose because the bigger engine had to work less hard


Maybe the prop on the new engine was a proper sail prop and since a two stroke will be more more efficient at partial throttle since less intake air/fuel mixture is pushed back out the exhaust port unburnt it will be more efficient and that's why you saw such a big improvement.


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## sawingknots (Feb 24, 2005)

i don't know the why,but the 6 definately strained


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## Flybyknight (Nov 5, 2005)

It's all in the prop.
The prop pitch is critical!
Most small outboards are designed for dinghies and the pitch varies from 7" to 8&1/2".
In a heavy sailboat it's like starting your car in 3rd gear.
A 6" pitch is perfect for your 6 hp application.

Dick


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## joethecobbler (Apr 10, 2007)

I'm going with the prop pitch issue as well.
also there is a different torque issue with a 2 stroke or a 4 stroke.


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## safira (May 10, 2010)

interesting posts here ... I have a 40 foot morgan that is 10 ton net and I use a 8hp 4 stroke honda on it, I may only go about 3.5 to 6 knots but that is fine as I use it very little anyway. The trick to useing a small engine is go with the tides or currents whenever possible. It is a sailboat so I use the sails, kind of figure that is what they are there for.
I got rid of the perkins 108 after she thru a rod and I think it is the best thing I ever did. Now i have storage where the inboard used to be. The extra stowage comes in handy for circumnavigating. The old tanks are used for gas instead of diesel. It takes me about a year to year and a half before I need to refuel. I run the boat engine, a genset and the dinghy engine from the tanks.
As with everything there is good and bad ... just go with the flow


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