weight ratio's front to back?

[magoo]

any good rule of thumb about weight dispertion?
ive got a 1983 14' smokercraft alaskan thats pretty built.ya know console,deck,seats, etc.dont know what it weighs.
i took off a 25hp merc and replaced with a 40hp evinrude.motor weighs i guess somewhere around 180lbs.merc weighed 125 or so.with the merc it got up and planed well.im a bit worried about the extra weight of this motor.
is it all trial and error to get the right weight dispertion to the front so i dont ride bow high?or is there some kind of equation?
i cant have anybody ride up front while under power,its a completely flat deck used for standing only.
i plan on relocating batteries to the front.leave the gas(6 gal) in the rear.

 

[CATransplant]

Re: weight ratio's front to back?

With that little amount of weight difference, I'm betting your new 40 will do just fine. You might have to trim it in one notch, just to push the bow down, but maybe not even that.

I'd try it out before doing anything else.

 

[INJUN]

Re: weight ratio's front to back?

What 'CAT' said.
Also check the capacity plate for max hp.

 

[magoo]

Re: weight ratio's front to back?

What 'CAT' said.
Also check the capacity plate for max hp.

says 35hp recommended.
i couldnt pass up the deal on the 40.not a whole lot difference in a 35 vise a 40 weight wise.
and im not an animal so i wont be running it at WOT through the chop.im not trying to kill anyone.just get where i got to go.

 

[stubblejumper]

Re: weight ratio's front to back?

The outboard rating system changed around 1983 from horsepower at the flywheel to horsepower at the prop.The difference is normally in the 10% to 15% range.So if you are using a new 40hp,on a boat rated for an old 35hp,you may actually be adding up to 10hp more than the boat is designed for.

 

[fdmsiv]

Re: weight ratio's front to back?

The short answer is no, there is no formula to tell you how to shift weights. For displacement craft it is much easier, but once you boat goes on plane, all of the disp. eqns are out the window. In the time it would take you to weight your boat and everything in it, you could probably do a couple of runs and shift things around to your liking.

 

[magoo]

Re: weight ratio's front to back?

The outboard rating system changed around 1983 from horsepower at the flywheel to horsepower at the prop.The difference is normally in the 10% to 15% range.So if you are using a new 40hp,on a boat rated for an old 35hp,you may actually be adding up to 10hp more than the boat is designed for.

86 evinrude 40hp
i have a very strong transom, but i am a little concerned about being a bit stern heavy.not so worried about power,im really probably going to rarely use it unless the water is glass.and im gonna check the boat regularly for rivet failure.its really solid right now so i should be ok.
should be a fun little boat, again.