Maximum HP on rebuilt transom

[ali'i]

Just bought a fully restored, approx. 40 year old, 14" fiberglass runabout, (have atatched a pic of an identical boat), as my camera isn't working. It has a professionally rebuilt 15" transom, the original decal on the boat says maximum 60 hp, but doesn't list a maximum engine weight, I am thinking of raising the transom to use a 20" shaft by way of an professionally made aluminum plate, (like a jack plate) and being that motors of early 1970's were lighter than todays motors, the max rating of 60hp would have been for a 2 stroke, would I be able to use a mid to late 1990's 50hp 4 stroke, that might way in the 200-245 lb range. I want to go with 20" as there is a far better selection to choose from. Thanks

 

[steelespike]

Re: Maximum HP on rebuilt transom

If your going in the 90s the motors will likely be carbed so emissions will be pretty much a wash.
The 2 stroke will be faster out of the hole, lighter, fewer moving parts,fewer and less complicated service intervals.
A 60 will be about 240 lbs. either way 4 st or 2 st.
Whatever weight it won't bother a healthy transom.

 

[ali'i]

Re: Maximum HP on rebuilt transom

I guess its not how much weight the transom can handle, but how much lower in the water will it be with a newer motor on it, being only a 15" transom, that was designed when a 60 hp weighed, from info I found online only around 150 lbs, and now seem to weigh around 200, or even 245, like the 1996 Johnson 50hp I am looking at, add to that another 50 lbs for a kicker, that's 300 lbs on the rear of a boat that was rated for a late 1960's, early 1970's 2 stoke 60 hp, won't the rear of the boat be sitting too low the water?

 

[steelespike]

Re: Maximum HP on rebuilt transom

You could add about an inch to the transom by simply fitting a piece of wood to the top of the transom and mounting the motor an inch higher.With the motor firmly bolted to the transom the trim piece is just a filler to raise the transom a little.
I have a 57 Crestliner 18ft utility with a 15" transom with a 1965 50 merc. The boat was occasionally used as a fire boat.The motor was already raised about an inch.
It would have a 2 cylinder pumper,a pilot and a hose man and may have been required to operate in rough conditions.
He had a fabric skirt made to fill the cutout of the transom It is fitted to the motor.It is not 100 percent effective but works very well.