Welcome! Need support, you got it. Or share you ideas and experiences.
I tried to post this earlier and maybe this is a duplicate. I'm looking for opinions on putting an 18 hp tohatsu outboard on my 11'4" whaler. It now has a 15 hp merc that doesn't cut it. The tohatsu weighs about 20 pounds more. The boat is "rated" for a 10 hp but that was a while back when motors were much heavier. I need enough power to put 2 people with camping gear on plane.
I have a 11'4" boston whaler with a 20 hp it flys I think you should go with the bigger 20 hp you will thank me in the end
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OK, a couple of ideas on getting your Whaler to scoot over the water better.
1- Not sure going from 15hp to 18 hp will do a whole lot. Try to figure the weight of the boat (a 13' Whaler is about 320lbs), add the motor weight, the fuel tank (w/fuel), the passangers and other gear. Then divide this total by the horsepower of the outboard. If you get around 17lbs per horsepower, you are in the optimium range for power to weight ratio for moving at a decent speed. Me thinks around a 25hp will do the job--But that may be too much engine for the boat--Above all--Boat Safety First.
2- We live in the go fast boat capitol of the world. Some big bad Gold Cup hydros are based here (Seattle WA USA). So making boats go fast is an occupation in these parts. Something I have noticed is most outboard motors are badly hung on their transoms... Here is what I do: With the boat out of the water and on the trailer I view the motor from the stern. I measure to be sure the motor is centered. Then I look at the height of the motor cavitation plate. That's the horizontal plate above the propeller on the motor skeg. For the most zip the top of the plate sould measure about 1" below the the bottom of the boat (3/4" is optimium on my boat). Yours doesn't...? Then the motor needs to be raised--vertically--not 'tipped' back and up. This means using a wedge under the engine braket about the width of the transom to gain height. Once agin common sence and good judgement need to be used here--the cinch screws of the engine must have enough 'bite' on the transom to keep the motor on the boat (!). A good idea at this point is to have the motor always tied to the boat. So if your Merc's prop is a bit too deep in the water and powering at a bad angle, this adjustment--done a small rise at a time until you hit the 'sweet spot'--will give better results. (The next thing is to add a little bit of a 'cup' to the right part of the trailing edge of the prop... But that's another story.)
3-How about talking to Boston Whaler folks...? Go to the Boat Events Calendar on this site and look at the August listings. There is a Boston Whaler Rendezvous scheduled. Send an e-mail to Dick Peterson and ask if any person from his group might post their experience to your post here...Google.com search engine comes up with some Boston Whaler sites, try there for more info.
Well, hope the above was a bit helpful and thanks for not giving up on your post! Let us know what changes you make and how they go.
Thom V "...Life's a Little Dry without a Small Boat..."
I happen to own 2 each - 13ft 1963 Boston Whalers that I purchased for $500.00 each within 1 week of each other. They are both original and have the original 35 hp twin cylinder Mercury's mounted on them. I have found that one out performs the other only because of a 2 blades bronze prop. I have to tell you that I did put a 4 bladed aluminum on the other but it still cannot keep up. A 35 is not too big a motor for the 13 footer but I would hesitate to go much larger. I did consult a dealer and he stated that the 35 was the max hp for the 13 ft whaler of that vintage. Good luck to you and I hope this helps. Keep on boating. jon
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