Bolting motor to transom

[Austinblake603]

Hello everyone,
I’m new to owning a boat so if this is a stupid question then fire away haha. Just have no one else to ask.
I’m re doing a 97 Grumman 18FNF. I got a 97 40hp Johnson to put on it but the boat has never had a bolt on motor.
My question is : do I just drill 4 bolt holes and bolt it up? Or do I need to put a plate behind it?
Also the channel on the motor that the transom would sit in is wider than what’s on the boat. So do I have to build that out with marine plywood so make it snug? Or do I just bolt it and let the bolts do the job ?

 

[racerone]

Just 4 bolts 1/2" hold it.------4 bolts will hold a 150 HP so should be adequate for a little 40 HP motor.

 

[ahicks]

I would add that leaving a 1/2" or so gap over the top of the transom (between motor and transom) is a pretty common practice.

 

[Austinblake603]

I would add that leaving a 1/2" or so gap over the top of the transom (between motor and transom) is a pretty common practice.

Okay thank you!

 

[Austinblake603]

I would add that leaving a 1/2" or so gap over the top of the transom (between motor and transom) is a pretty common practice.

Okay thank you!

 

[Scott Danforth]

in addition to drilling the holes, you may want to seal the holes with 3M 5200 and use bolts with nylock nuts.

 

[Austinblake603]

Stainless bolts or grade 8+ and replace them every year?

 

[Scott Danforth]

what ever you want. either would work.

 

[Austinblake603]

what ever you want. either would work.

Okay thank you for the help!

 

[ahicks]

If you go with the 5200 sealant in the holes, which is a good plan, changing the bolts annually is going to make a mess. Use stainless....