Correct way to bolt engine to transom

[ali'i]

I am going to mount an approx. 235 lb, 2000, 50hp Evinrude, w/power tilt, 20" shaft, on a rebuilt, 15" x 1.5" transom using CMC, 5? Vertical Extension, and 1/2", grade 8, s/s bolts, what is the correct way to insert the bolts, is it nut on the inside of transom or outside. I have seen both, and some with both inside for top and outside for lower. I would think mounting with nuts inside to help protect threads from salt water and damage. And do I use washers at the nut end and bolt head end, or only when mounting on the inside against fiberglass, or again, is it both inside against fiberglass and outside against motor or ?? Thanks

 

[boobie]

Re: Correct way to bolt engine to transom

My first question would be, what does CMC say about it?? Over the years I've seen them done both ways but it's your choice.

 

[Chris1956]

Re: Correct way to bolt engine to transom

I have never seen grade 8 stainless steel bolts. Grade 8 bolts are steel, as far as I know. You may be able to get galvanized grade 8 bolts. Obviously use fine thread bolts with nylon lock nuts and washers. Oversize washers on the fiberglass is a good idea.

BTW - you really do not need grade 8 bolts for that application. Stainless steel bolts are about grade 2, and will be plenty strong.

 

[Bosunsmate]

Re: Correct way to bolt engine to transom

I cover the bolts in gasket glue when i slip them through the fibreglass transom so no water can work in there and rot the fibreglass

 

[Tim Frank]

Re: Correct way to bolt engine to transom

I've seen a post in here in which someone said "put the head of the bolt inside the boat, nut outside"....reason given was that you then have less of a protrusion inside the boat and that stiff can bang into the bolt end and possibly get punctured....gas tank etc.....or a shin. Makes some sense.

I did it the reverse way on my boat because of the way I redid my transom and it was much more reliable to seal the bolt with the head on the outside.

Your results may vary....