new motor on an old boat

[redjek]

I have a 1974 chrysler satellite (15'). I want to put a new motor on it. the boat is rated for 75 hp. the old 75 horse weighs 300#. the new one weighs 400#. the transom seams very solid and i do plan on adding a backer plate for more strengh. will the additional motor weight cause more stress on the transom? Has anybody done this before?

 

[Bob_VT]

Re: new motor on an old boat

Welcome to iboats.....

A backer plate? That is a band-aid repair and does not add strength only weight.

You need to completely inspect your transom for signs of rot and use bore holes to verify. Based on the weight yes new 2 strokes are close to 400 and 4 strokes are slightly heavier.

Yes the additional weight is more stress and so is the new power. New 75 hp motors are 75 hp at the prop or equal to a 1974 vintage 85-90 hp at the head.

 

[redjek]

Re: new motor on an old boat

Thanks Bob. I appreciate your timely response. I don't know what else to do but use a nice aluminum backer plate. Thanks for your knowledge.

 

[ezmobee]

Re: new motor on an old boat

If your transom is indeed solid and not rotted, it should be able to handle the new motor without modifications.

 

[alaskanassassin]

Re: new motor on an old boat

My 1978 Grady White is rated for a 225, and I am running a 2004 Merc 200hp 2 stroke (405lbs). If I had to repower, I would use a 150 or 175 instead. I can't ever go wide open 60mph in the seas we get here, and a little less weight on the stern would help stay drier. My splashwell gets USED, especially backtrolling to jig the reefs and rockpiles! I would gladly lose 10mph to gain a few more inches of freeboard. If your transom and stringers are solid, the boat should handle it just fine but think about the weight esp. with a 4 stroke.