What size motor do I want?

[handle]

I have an old 15' StarCraft center console aluminum boat weighing in about 460lbs. without motor. I am currently running an 06' 40 hp 200lb. Yamaha 4 stroke motor; thinking about an up grade in the motor. The motor seems a little heavy for that package but does well, any suggestion's

 

[64osby]

What is the year and model of the hull?

There should be a capacity plate attached to the hull that will state the max weight load, max passengers and the max HP.

 

[handle]

The hull is a 15' Startrek V, rated for max hp 45 . The tag states 1100 lbs.for persons gear and motor. I haven't exceeded the motor rating but the engine (40hp fourstroke)seems heavy on that transom. I keep looking for ways to lighten the stern. This unit has to be pulled up on a cradle when the lake gets rough. Most of the new 30hps aren't much lighter than my 200lb Yamaha so I might be over thinking this weight issue. The battery sits in the stern @ 38lbs. would a lighter battery be possible?

 

[Teamster]

Maybe try moving the battery and fuel tank forward,....

 

[handle]

Length of battery cables limit the distance the battery can be moved forward and the fuel tank is already stationary, mid section of the boat. Manufactures seem to keep the cables short to limit electrical drop from battery to motor. Good idea though.

 

[64osby]

New longer, thicker cables would allow you to move the battery anywhere you would want.

As long as the rated HP is not exceeded you should be fine. The HP limit has more to do with the stresses that are transferred to the hull, not the weight of the motor.

 

[Chris1956]

Gee, I immediately thought a 2 cycle 50HP Merc IL4 would be good, but that goes over your HP limit. Merc did make some 45HP versions of that inline motor.

 

[Guest]

Chances are that boat was designed for a 2 stroke motor. The trouble with four stroke engines is that they're heavy and can weigh up to 50% more than their 2 stroke counter parts. You could go with a 2 stoke 40 or 50 Johnson or Evinrude (187 lbs - same motor platform.) and while you may not lose that much weight, these OMC motors have the 2 stroke punch that a four stroke Yammer will never have.

Older boats like your Starcraft often struggle with contemporary power because they weren't meant to handle the heavy weights of the newer 4 stroke designs. Contrary to what most 4 stroke dealers will tell you, most later model Merc and OMC 2 stroke motor parts are still readily available.

 

[handle]

The original package came with a 2 stroke 25hp evinrude. You are right the fours are heavy but the way of the two stroke is fading except for the new etecs but they are just as heavy as the fours now. Some of the new 25s and 30hp aren't much lighter than my 40 yam @196lbs. I agree though I don't think the transoms and or the hull were designed to handle that extra weight . With the max rating of 45hp, I thought I would be safe with a 40hp. The unit goes well and I am not sure if a smaller lighter motor will do the same job. When I rebuilt the package I went with a new motor for reliability. Only wished it was fuel injected and lighter ! Liked your input.

 

[Guest]

I completely agree with you regarding the weight of the Etecs. A 25hp Etec weighs just as much as my previous 1999 50 Johnson(!). Unfortunately, its unlikely that a 4 stroke will ever achieve the power density (i.e. weight/horsepower ratio) of the conventional 2 strokes of yore. As a result, boats such as yours intended for 2 stroke power will be at a somewhat disadvantage when repowering with contemporary 4 stokes. You're right that this boat would not perform better with a smaller motor, but it would with a 2 stroke (carbed) of similar power. Since you've made the investment in the 4 stroke and you're happy with the performance, I'd keep what you have. I've spent my whole life running OMC 2 strokes from 2 to 200 hp, I've run some 4 stroke engines of similar HP and they disappoint me. That's why I keep my 2 strokes, and I have no problem getting parts for them. I've run these things long enough to know that with proper care, they're every bit as dependable as a new motor.