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Author Topic:   15-footer with 30-HP
fina posted 01-06-2015 02:47 PM ET (US)   Profile for fina   Send Email to fina  
How would [a c.1985 Boston Whaler 15-foot] boat perform with a 30-HP four-cycle outboard engine with trim and tilt?
tedious posted 01-06-2015 03:04 PM ET (US)     Profile for tedious  Send Email to tedious     
Performance will be minimally acceptable; will hit around 24 to 26-MPH with a light load. You may have trouble planing at all with more than one or two people on board; obviously it would depend on how much they weigh, and how much other gear you have.
fina posted 01-06-2015 03:29 PM ET (US)     Profile for fina  Send Email to fina     
Thank you. Would [a 15-foot Boston Whaler boat with a 30-HP four-cycle engine] appeal to someone getting their kids into boating for the first time[?]
tedious posted 01-06-2015 04:35 PM ET (US)     Profile for tedious  Send Email to tedious     
The 15-footers are great boats, but I'd want to go with a minimum of 40-HP. It seems like you might be fighting to plane sometimes, which is no fun and not a good way to teach, either.

Have you thought about a 13? They are a lot easier to find, are cheaper, and run well with a 30-HP. They also are more stable side to side, and have greater carrying capacity than a 15. That might be more practical for kids.

The 15 is a thoroughbred--fast and maneuverable--but not very stable or forgiving.


jimh posted 01-07-2015 09:05 AM ET (US)     Profile for jimh  Send Email to jimh     
A 15-foot Boston Whaler would be a wonderful boat for introducing boating to your children. It won't be very fast with just 30-HP. If you are thinking about using it for activities like water skiing or other uses where you have to pull someone in the water, it will be under-powered.

The boat will get on plane with 20-HP. Minimum planing speed will be around 22-MPH. With only 30-HP you won't have too much difference between just getting on plane and top speed of around 26-MPH.

When I was looking for my first Boston Whaler boat, I was searching for a 13-footer. I stumbled onto a 15-footer, and I am glad I did. I think the 15-footer is really a great little boat.

fina posted 01-07-2015 11:21 AM ET (US)     Profile for fina  Send Email to fina     
thanks for the info

i think i am going to sell the 30hp and get a bigger motor

jimh posted 01-08-2015 10:25 AM ET (US)     Profile for jimh  Send Email to jimh     
My 1976 Boston Whaler SPORT 15 had a 1976 Mercury 500 50-HP two-cycle outboard. It was plenty fast for me. When you are going 35-MPH on the water on an open boat with low gunwales like the 15-foot Boston Whaler, there is an enhanced sensation of speed. The boat's top speed was about 34-MPH, but it seemed very fast.
tedious posted 01-08-2015 12:12 PM ET (US)     Profile for tedious  Send Email to tedious     
My big concern with the 30 on the 15 would be that it wouldn't plane at all with a couple of people, a couple of kids, and some gear on board. That would be annoying and potentially unsafe in rough conditions. Of course it depends on how big the people and the kids are!

Lightly loaded, I think it would be fine, and Jim is correct that the 15, with its low seating position and gunwale height, feels faster than you're really going.

A conservative approach would be to try the existing motor in the spring, and see if it meets your needs. Then if you decide to sell it, you'll get a better price than you will in the middle of the winter.


jimh posted 01-09-2015 01:30 PM ET (US)     Profile for jimh  Send Email to jimh     
Tim's comments are very apropos. On small boats, the weight of the crew and gear becomes a very high percentage of the bare boat weight. Performance is always in proportion to power-to-weight ratio. The addition of 500-lbs of passengers and gear to a hull that only weights 500-ls itself is going to have a very big impact on performance, as the weight will practically double.
mkelly posted 01-10-2015 05:57 PM ET (US)     Profile for mkelly  Send Email to mkelly     
I have the same boat, they came standard with 70 HP OMC (Evinrude/Johnson)two cycle engines back in the 80's. We recently repowered with Yamaha's F60 (four stroke) & could not be happier. I would go with the newer but same weight F70 to get a little extra zip & out of the hole. Four strokes are not that great out of the hole but that HP to weight ratio buries all that problem. Get the F70 or go with the 60 HP ETEC that represents a similar weight.
tedious posted 01-14-2015 08:46 AM ET (US)     Profile for tedious  Send Email to tedious     
For reference, I have an F70 on my 15, and while I like the motor a lot, if I were to do it over again I might consider an F60 for my usage model.

Given the hull configuration of the 15 and the apparent power curve of the F70 (it mostly makes its additional power in the top of the RPM range where the 4 valves provide an advantage) I find it hard to make use of that extra power. You need to be running fairly light, on flat water, and trimmed out pretty far - and that's a combination I just don't experience all that often.

I boat mostly in the ocean, and while it's not all that rough, it's rarely flat. Those of you who have 15s know that one of the big challenges is keeping the boat on the water at speed - depending on how you're loaded, the minimum planing speed may be enough to take you airborne, which is not necessarily all that comfy.


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