Engine size for Wooden Boat?

[Neil2177]

I’ve just purchased a hand built clinker built wooden boat in Gippsland Victoria Australia for inshore saltwater fishing and generally enjoying the water.

I’m receiving advice from buy a 25HP to 40HP outboard.

Would appreciate guidance!!

Boat is 14 foot long and weighs 220 Kgs. Transom to bottom of keel is 60cm.

 

[briangcc]

I've never heard anyone say they bought too big of a motor...but I've certainly heard many lament they should have gone bigger. So if the boat will take it, I'd go for the 40HP.

 

[Neil2177]

I've never heard anyone say they bought too big of a motor...but I've certainly heard many lament they should have gone bigger. So if the boat will take it, I'd go for the 40HP.

I agree but is there a formula to work it out or measurements I can use?

 

[cyclops222]

What does the builder recommend with your weight and gear and fuel tanks to be carried? Style of hull ? V, very deep V, other. Weight of empty boat ? Approved # of people or total weight of gear and people ?

 

[Neil2177]

Boat builder was a very talented carpenter who only out a 7hp on it for an afternoon. Then sold it.

I’m working on 220 Kgs for boat. I’ve weighed the boat on a weigh bridge. 3 people, outboard, fuel and gear 380 Kgs. Giving a total weight of 600 Kgs.

 

[Neil2177]

Here are some photos.

 

[JASinIL2006]

That is some gorgeous woodwork in that boat!

 

[Scott Danforth]

I agree but is there a formula to work it out or measurements I can use?

yes, the IMO has formula to determine max hp. CFR 33.183 mirrors the IMO rules.

since the boat is a tiller and not a console steer, and is not a flat bottom boat the formula in your case would be (Transom Width x Length at water line x 0.8 ) - 25

estimating your transom at 4 ft. your length at water line at 13.6 ft your maximum hp would be 18.5

for all other capacity calculations, look up the boat builders handbook.

 

[Neil2177]

Thank you Scott, very helpful and much appreciated.

 

[rolmops]

I agree but is there a formula to work it out or measurements I can use?

There is a formula if you go to the United states coastguard site and look for information about do it yourself boat building there is a lot of info and there is a formula about the maximum horse power allowed on a boat. It even has it for different types of boats.

 

[rolmops]

the computation method is best to use. You multiply your boat length by the transom width. Then you take that number, which is known as the “factor,” and match it to a horsepower capacity according to the Code of Federal Regulations Table 183.53 — Outboard Boat Horsepower Capacity, shown below.Jan 25, 2022
This done in feet not centimeters. I have the thing hidden deep in my book pile, so I just copied this from a site.

 

[tphoyt]

That is some beautiful work but how thick is the transom? I don’t know that I would trust a 40hp and anything less than 2 inches thick.
Just my 2 cents

 

[Stinnett21]

Displacement hull and heavy. I doubt anything more than a 20 would buy you much.

 

[Texasmark]

I’ve just purchased a hand built clinker built wooden boat in Gippsland Victoria Australia for inshore saltwater fishing and generally enjoying the water.

I’m receiving advice from buy a 25HP to 40HP outboard.

Would appreciate guidance!!

Boat is 14 foot long and weighs 220 Kgs. Transom to bottom of keel is 60cm.

40 hp isn't a lot of power for that boat. In my boating circles, 40 hp on a 14-15' boat isn't uncommon, even on lightweight aluminum and fiberglass boats. As others have said, you never seem to have too much power to have a good time.

 

[airshot]

In my 60 plus years of boating, most every boating accident I have witnessed is from folks not knowing how to handle to much HP !!

 

[rolmops]

There is another very important factor to be considered. Insurance companies will often check the horse power capacity of the engine that was on the boat at the time of an accident. If the the hp is bigger than what is allowed according to calculations mentioned above, The insurance company has the right to refuse to cover a claim.

 

[JimS123]

I had a similar size and weight boat years ago and originally had a 40 on it. It did have a forward wheel, though, not a tiller.

When I had engine problems, I traded it in for a 60. THAT boat was now squirrely.

Another tinny I owned was rated for a 25. THAT was also squirrely. I settled on an 18.

So, count me in as someone who said (twice): "I wish had a smaller motor!"

Back to the OP...
JMHO, that boat would do just fine with a 25 4-stroke.

 

[Scott Danforth]

this site will not condone over powering. the IMO rules exist for a reason.

 

[airshot]

I had a similar size and weight boat years ago and originally had a 40 on it. It did have a forward wheel, though, not a tiller.

When I had engine problems, I traded it in for a 60. THAT boat was now squirrely.

Another tinny I owned was rated for a 25. THAT was also squirrely. I settled on an 18.

So, count me in as someone who said (twice): "I wish had a smaller motor!"

Back to the OP...
JMHO, that boat would do just fine with a 25 4-stroke.

My current 16' tinnie is rated for 80 hp....I have a two stroke 40 hp Merc and it does 31 plus mph. In flat water it can get squarely and in a breeze down right scary at times. Often thought how scary it would be with an 80 hp outboard on it....heck even a 60 might be scary unless you had a very heavy load !

 

[Scott Danforth]

Guys, this is a 14 foot hand- built wooden boat with a transom that is about 3.5- 4 ft wide and is tiller steer. If it was a tinny, it would be a 14' row boat.

Not a wider aluminum boat with a console.