what bolts to use

[DUNK51]

been working for about six hours removing broken bolts from my engine and I am ready to start puting things back together. wondering what bolts may be better stainless or steel? using this boat in fresh water. any thoughts on this?

 

[F_R]

Re: what bolts to use

Surprise, stainless will corrode/sieze/break worse than steel. Reason: It is a more dis-similar metal than the aluminum it is in. The dis-similar metals is what causes the corrosion. The stainless itself is not what corrodes, of course, but the aluminum around it. On the other hand, yes a steel bolt will rust. All of the above is why the factory uses stainless where it is easy to see, but uses steel where it is hidden under the hood. Usually. There are exceptions, for instance the bolts holding the powerhead on. Usually steel, at least they are easier to get out than if they had used stainless.

 

[DUNK51]

Re: what bolts to use

thanks for the info, I would have gone with stainless steel not knowing and not wanting to go through this again. I am using real steel! any coatings that will help?

 

[Chris1956]

Re: what bolts to use

Dunk, Look at the bolt heads of the original bolts. Replace with the same grade bolts. Some antiseize may help.

Ironically, my '59 Johnny was all stainless steel bolts, except the crankcase bolts. The casing, midsection and heads all had SS bolts. After 45 years, it came apart w/o issue, although I needed a impact driver for the 1/4"-20 screws.... I used permetex #2 on all the threads...

 

[danoutbard]

Re: what bolts to use

Surprise, stainless will corrode/sieze/break worse than steel. Reason: It is a more dis-similar metal than the aluminum it is in. The dis-similar metals is what causes the corrosion. The stainless itself is not what corrodes, of course, but the aluminum around it. On the other hand, yes a steel bolt will rust. All of the above is why the factory uses stainless where it is easy to see, but uses steel where it is hidden under the hood. Usually. There are exceptions, for instance the bolts holding the powerhead on. Usually steel, at least they are easier to get out than if they had used stainless.

Very interesting to learn from you guys
Thanks

 

[F_R]

Re: what bolts to use

I could add that if it ever does become necessary to drill out a broken bolt, a stainless one is MUCH more difficult to do. Unless somebody puts in higher than grade-5 steel bolts (completely unnecessary). BTW, not doubting Chris' word, but I've worked on umpteen hundreds of '59 era Johnsons and have never seen one come from the factory with SS head bolts. I'd say somebody else go to it before now.

 

[Chris1956]

Re: what bolts to use

F-R. Both my '58 and '59 Fat fifty's had all stainless steel screws on the midsection cowling, headbolts, shift lever cover, gearcase seam, gearshift belcrank, carb cover, etc. Most everything else that was not sandcasted was brass.

Most of the crankcase and water jacket bolts on my Mercs are grade 5 steel. The upper motor mount bolts are grade 8 steel. Very litle stainless above the waterline.

 

[Chris1956]

Re: what bolts to use

I do not have any way to know if the SS head bolts were original. They did look it, but a lot of the paint had fallen off over the years.