Runabout engine to Pontoon swap

CheapestBoater

Recruit
Joined
Aug 7, 2018
Messages
3
I have an old Rally by Cruisers 16' runabout with an 85 horse Evinrude. The boat is beginning to have some issues, soft floor, in the back, and I believe the transom is failing. But, the engine is in great shape. I am not afraid to work on things, but don't feel that the boat is worth the expense of re-decking. So, I am thinking of buying a pontoon with a bad motor and putting my Evinrude on it. What obstacles am I in for?
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
Someone more expert than me will come along. But I've swapped engines on my old pontoon boat twice. Biggest issues were:
  • Being sure the engine pod (transom) was strong enough for the engine.
  • Getting the prop at the right depth.
  • Matching the controls to the engine.
  • Routing the controls to the engine.
  • Pairing up existing gauges with new engine.
 

CheapestBoater

Recruit
Joined
Aug 7, 2018
Messages
3
Ok, so, how do you determine prop height? I've never fooled with a pontoon, but that transom on the back of those things looks incredibly simple to me. As far as the controls, I have the box, so it seems that longer cables would be the ticket, unless I am missing something? And, since the Rally is really old, there a'int a gauge one!

I figure when I'm done, I have a 16' runabout trailer for sale with a free boat on it.
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
The usual starting position is with the anti-ventilation plate even with the bottom of the engine pod.
350px-Outboard_diagram-01.svg.png
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Engine weight is another big factor, especially when working with an older 'toon that has small diameter pontoons. When picking out a new (to you) 'toon, look for the biggest tubes you can afford. Be leery of (older) boats with 21" or smaller. They're very easy to overload, especially with an 85 on the back. In a perfect world, when looking at it from the side, no more than half of the pontoon height will be under water in the rear. 24" or bigger your best plan.
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Welcome to iBoats! :welcome:

Make sure the pontoon is rated for at least 85 HP. Then, as long as everything is structurally sound, you shouldn't have to worry about the weight of the motor.

You will almost certainly have to get a new prop with a lower pitch.
 

CheapestBoater

Recruit
Joined
Aug 7, 2018
Messages
3
Thanks for the tips. Great illustration HotTommy. Funny thing, since I know next to nothing, just asking the question brings fear. Lots of times I have looked for advice on forums and been treated like a moron. Thanks to you folks for being civil with me.

The old runabout has been a ton of fun. Got three years out of a boat with $2,000.00 invested. That old motor runs better than most I am around on the lake except the shiny new ones, so the idea of using it on a different boat appeals to me since I know it and understand it.
 

icwingman

Seaman
Joined
Aug 21, 2017
Messages
61
google the boat you want to buy and get the specks, then it just cables and steering have a great time with your new boat
 
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