Can you put too much HP on a boat?

[jiminmontana]

The 1957 Lone Star Caribbean that I am restoring is rated for 150 HP. My motor is a 1964 Johnson Meteor 90 HP, and that seems a bit on the slow side for a 19 footer. I have access to 2 more of the same motors for $100 each. They need work, but the key parts are good and kits are available for the little stuff. I am going to buy one anyway for replacement gears if needed later.

This model boat was ideally fitted with 2 motors of 75 HP. The boat is rated for 150 HP. If I add balast and beef up the new stringers, gunwales, thick decking, and new transom with a steel plate, can I put 2 motors of 90 HP on the back?

Also, a kicker would be a final thought when I don't want to run that much power. Too much weight for all three? The 1964's weigh 227 pounds each and the kicker is 47. Anyway, I have decided to fix this boat up right. The only real change is to put in a 35 Gallon Moeller tank below deck. And that's only because the 55 G is too tall! Starting on the transom Saturday -- Lord willin'.

Pics are on my blog as listed below my signature. Thanks for the good advice and contacts lately. I am a CADET! and need the good replies.

 

[tashasdaddy]

Re: Can you put too much HP on a boat?

2-90's is 180 hp. i don't belief that 50 year old hull will take that much. you can only do so much bracing. hang a 140 -150 on it.

how do you know the gears are good in the parts motor, it is just a gamble, that i have lost before.

 

[Frank Acampora]

Re: Can you put too much HP on a boat?

QUOTE: "Too much horsepower is NEVER enough!" UNQUOTE

If you properly re-engineer and reinforce the transom and also beef up the hull, two 90s should do it. After all, it is only 30 more than the rated. However: What is the weight difference between the two 90s and the two 75s that it was meant to hold?

Just plating the transom with aluminum is not proper reinforcement. You must devote some time and thought as to how to place metal and where to place it to distribute thrust loads through the transom into the hull. The transom is not an isolated part of the boat. In most cases it functions combined with the rear deck and splashwell to distribute thrust loads.

See that little boat in the avatar? It has twice the rated horsepower on the transom. The transom is plated on both sides with .080 aircraft grade aluminum and re-filled with resin. It is then angle braced to two plates that run the full internal length of the splashwell so the whole back end of the boat absorbs the power. And: the whole rear deck and hull is glassed together. Even so, weight is still an issue as she sets below the rubrail when at rest. And the boat is very unforgiving of operator error. So: Think twice before starting on the twin engine upgrade--not saying don't do it, just saying think through all the pros and cons.

However: You also need to account for personal liability/negligence in case of an accident and the P.I.A. factor of the local boat police if they decide to check your hull and capacity.

 

[Barnacle_Bill]

Re: Can you put too much HP on a boat?

What Frank said. Plus the Coast Gurad wouldn't care what you put on there but the insurance companies would have a field day with you if you were ever involved in an accident.

 

[JB]

Re: Can you put too much HP on a boat?

Well, you are underpowered with only 90HP on a boat that is rated for 150HP.

Generally, that boat needs at least 115HP to perform satisfactorily.

HP rating on a boat depends on a lot more than how strong the transom and stringers are. 2 90HP engines would be too much power and probably too heavy.

Do some engine trading and either put two JohnnyRude 70s or a single JohnnyRude up to 150hp on her. Be sure that the transom is sound before you do anything.