Sealing boat motor holes

[JSGOLD]

We are removing a 55hp motor that has never been right and replacing it with a 9.9 remote as we frequent 10hp lakes most of the time and was curious how to seal up the holes in the transom since the 9.9 and 55 have different mounting holes... Two of these will be below the water line. Was thinking maybe marine silicone and large bolts but not sure that would work.

 

[jbcurt00]

I'd use a stainless bolts, fender washers and a nyloc nut w 3M 5200 to seal below the water line.

Fiberglass or aluminum boat?

Either way, before mounting new rig, pay close attention to the transom wood when you remove the 55hp if its had water intrusion, it'll only get worse...

 

[Woodonglass]

Good Advice! ^^^ If the wood is good, I'd prolly do a more permanent fix and mix up some thickened fiberglass resin and fill the holes with it or go to Ace Hardware and buy some PC-11 to fill the holes with. But either way will do the trick.

 

[JSGOLD]

Thanks! it is an aluminum boat and so far as I can see no intrusion. I can see the nut/bolts in the lower area and no sign of seepage. Will watch when removing just in case. I was curious how I should seal around the new holes...Should have asked that in the original question I guess. The 9.9 has 4 holes but also clamps on. Was thinking of clamping it down and installing two bolts above the water line. Or should I use 4 bolts? Would the 5200 be Ok there or just marine silicone? I heard that 5200 is tough to remove.