Motor Swap

[Yammerhead]

I have a 75 fiberglass tri-hull that has had an 85HP Evinrude on it since it was new. I have taken it off and am going to put a 73, 85HP Merc on. Is there anything I need to worry about before I go and re-drill the transom? I assume that as long as I center the new holes in respect to the existing ones, it should be in the correct position? There are quite a few mounting tabs on the Merc to choose from. Which ones are the best to use? Is there such thing as a template for the mounting holes? Is there anything else a guy should be worrying about?

What's the best way to seal up the old bolt holes? RTV sealant or ???

Any advice is appreciated.

Thanks!

 

[Chris1956]

Re: Motor Swap

Use some marine silicone to seal the old bolt holes. The Merc should take 3/8" stainless carriage bolts with nylon lock nuts. Make sure the Merc is centered on the transom. If you have PTT on the Merc, it will need at least two more bolth thru the PTT Bracket. Seal all new holes with the marine silicone.

 

[tashasdaddy]

Re: Motor Swap

suggest 3m 4200 for sealer of new bolts, 3m 5200 for filling old holes.

 

[SpinnerBait_Nut]

Re: Motor Swap

On a '75 model boat, I would check the transom for water rot while I was at it.
If anyone has had the engine off for some reason and did not seal the bolts back, water has got in there.