Powerhead Bolts

yorab

Ensign
Joined
Jul 6, 2002
Messages
960
I'm going to replace all bolts in my 1963 75hp powerhead as I rebuild. How does everybody feel about aftermarket bolts? I have a Fastenal here in town that could get most standard bolts. I've already ordered original OMC connecting rod cap bolts but I'll probably get aftermarket for everything else if there is no problem in doing so. Are any of the bolts specialized in that powerhead? What strength/material should the bolts be? I don't have the bolts in front of me, but I imagine that the strength markings are on the bolt heads, though I'm not sure. Material would be very important for corrosion resistance. Thanks.
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,198
Re: Powerhead Bolts

Fastenal has good fasterners, take them with you and compare, stainless.
Steel into alum isn't critical like head bolts in a cast iron block on a car.
The head bolts in my car have to stretch, by torquing , then angle turn.
 

yorab

Ensign
Joined
Jul 6, 2002
Messages
960
Re: Powerhead Bolts

Yeah, the head bolts in my Stratus are the same torque-strain design. Not sure if this applies to my Starflite powerhead though.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,015
Re: Powerhead Bolts

If the head bolts are steel, they will be marked with the grade, replace with the same. If they are stainless, replace with SS. Make sure you get the exact same length and thread. Use some permatex #2 when installing to keep corrosion out.
 

yorab

Ensign
Joined
Jul 6, 2002
Messages
960
Re: Powerhead Bolts

I went to Fastenal today to order the Scotch-Grip 847 and to get the bolts. Nearly all of the old bolts stuck to a magnet, so we realized that they weren't stainless. However, after 47 years of being in the water and out in the humid air, none of the external powerhead bolts had any corrosion. Some of the bolts had a paint covering over the head, but many of the bolts were missing the covering yet there was no rust/corrosion. We were a bit perplexed as to how steel could do that so I called two local boat shops-one of which specializes in OMC. Neither one had a clue as to what these outboard bolts are made of and one guy acted ticked off that I would dare ask a question like that (?!?). I'm glad you guys are here!

Anyway, I decided to go all stainless to avoid corrosion. Also, in order to avoid galling at the interface of the stainless and aluminum, I bought Loctite Marine-Grade Anti-Sieze that is rated to 2400 degrees or so and is supposed to prevent galling in these situations. I hope that I made the correct choice for my bolts. If anybody thinks that this was a bad choice, please let me know! I can still take the bolts back until this weekend when I assemble the powerhead.

Lastly, I needed a few flange-head bolts but Fastenal can't get them in stainless. Is there any difference between using a hex-head with a washer and using a flange-head bolt? If not, then I'll just get the hex-heads and washers. Thanks.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: Powerhead Bolts

Do whatever you want, but if corrosion is a problem, stainless is worse than steel. They are further apart on the dissimilar metals scale. Once a stainless steel bolt corrodes in the threads, and you break it, it is much harder to remove than steel.

OMC reccommended their gasket seal on the threads. I never could understand why anybody would use anti-sieze. The friction is supposed to help prevent loosening. The gasket seal also helps make it "stick", and keep corrosion out.

The original bolts were steel, cadmium plated. Cadmium is outlawed now, so other materials have to be used.

You will find that OMC loved to use non-standard bolts. Meaning odd lengths, and odd length threaded portions. And those odd head styles you found.
 
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