Boat size vs Engine size

[TheForceGuru]

Hello everyone, brand new to the forum and actually brand new to owning a boat as well. Somehow I've managed to acquire four old tri-hulls in the last month so I'm like a sponge soaking up as much as I can from the great information on this site.
My question is about two of the boats I picked up...one is a 1971 17' Arrow Glass with an Evinrude 85hp that runs good and an average shaped hull. The other is a 1972(I think) 15' Glastron V-156 with a 70hp Chrystler that I can't get to fire yet, but the hull is in better shape than the Arrow Glass. The Arrow Glass has a max horsepower rating of 125hp and the Glastron's is 85hp. As far as the hull layout's are concerned I like the Glastron better even though it's smaller.
I've been kicking around the idea of taking the 85hp off the Arrow Glass and throwing it on the Glastron, but just curious what you all think of the idea? It seems like the Glastron would perform better due to it having the max horsepower but would it perform better when pulling a tube/skier? I wasn't sure what the performance difference would be "under load" since it's lighter?
Thanks for any insight anyone can provide!

 

[Maclin]

Welcome Aboard!

It will perform better in all scenarios in my opinion, but may need a prop pitch change for optimum.

Look at the controls and cables, Chrysler/Force may be different enough that you may want to swap it all over cables and all. The Arrow Glass being longer may take some looking into first.

Good luck!

 

[Scott Danforth]

welcome aboard. with all boats older than 15 years, you need to make sure the structure of the boat is rot-free and safe. the boats in your post are almost 50 years old. the stringers and transoms would need to be investigated before I would even worry about a motor.

 

[southkogs]

Assuming the hulls are in good shape, I think you'd like the 85HP on the Glastron. Saw a lot of 'em like that when I was growing up. We skied and tubed behind that type of setup. Depending on the size of the people in the mix, you may have some trouble getting a slalom skier up - but honestly, we used to ski 3 people (two skis each) behind a 15' with a 85HP tri-hull.

Welcome aboard.

 

[H20Rat]

You said the hull is in good shape, I'm not worried about the hull. How about all the soft squishy pieces inside the hull, mainly the transom and floor? Although not impossible, the likelihood of either of those boats being structurally sound is pretty low.

Anyway, I had that same glastron with a electronic push-button shift evinrude on the back. It was a rocket, up to the point it was dangerously fast. It easily pulled skiers/tubers around, there is so little weight you don't need much power.

 

[wahlejim]

I agree with the aforementioned opinions. I think your best setup would be the 85 rude on the glastron.... if the stringers and transom are solid.

 

[444]

I agree with everyone else. Weight won't be a big difference between the two motors so I would do the swap. I like the chrysler motors because I'm a mopar guy and I think they're neat but in every practical sense, including parts availability, the evinrude is by far the better choice. But like others have said, if your transom is mush the point is moot.

 

[redneck joe]

every single post here is valid whether structure or HP