1971 Evinrude 60 hp Rebuild.

[fire0501]

Yup I wanted to take the boat out this weekend but there was that knock again I couldnt help but tear the motor down and find that Piston one with the low compression was melted pretty good. So I think I may rebuild. On the underside of the pistons there is the M logo which I think is Mallory but not sure and the numbers are 316577 and I tried to do some searching and I come up with nothing I am trying to figure out what size piston these are and I measured them with the calipers and they are about 3.00 same thing at the top of the cylinder walls. could someone let me know if this is a stock bore and maybe where I could find this part so I can be sure before I spend a bunch of money. Thanks for the help in advance!

 

[orbanp]

Re: 1971 Evinrude 60 hp Rebuild.

The nominal bore size is 3". There are oversize pistons in .020" and .030" extra size.
This page shows the parts breakdown of your motor, including oversize pistons: 1971 Johnson Evinrude 60 hp Outboard Parts by Model Number
As for measuring the cylinder bore, you really should use an inside micrometer. With a caliper you will measure the cylinder where usually a ridge is, at the top of the bore where the rings are not sliding, and wear is negligible. Depending on the quality of the caliper it is probably OK to get the nominal bore size, i.e. if it is oversize already or not.
Cylinder and piston clearance is .0050" max to .0035" min according to the manual.

Good luck, Peter

 

[fire0501]

Re: 1971 Evinrude 60 hp Rebuild.

Thanks Peter. It looks like the cylinder walls just have some piston material on them with cylinder one really being the issue. Im hoping to clean them up and remove the aluminum with a good honing possibly with a ball hone and then stay with the std bore size. The part numbers on the piston is what has me though they are 3" or 2.98 as is the top of the cylinder but I cant find that part number anywhere. I plan to use the wiseco 3115ps If the cylinders are in spec after the hone.

 

[jbjennings]

Re: 1971 Evinrude 60 hp Rebuild.

What was the cause of the melted piston? Overheat due to lean fuel on dirty carb?

 

[orbanp]

Re: 1971 Evinrude 60 hp Rebuild.

Before you start honing, I would remove the smeared up aluminum from the cylinder walls. That would give you a better idea what you are up against.
Here is a thread about cleaning the cylinder walls with muriatic acid: Need Muriatic acid cylinder cleaning explained please...
I am sure iboats also has a number of postings on this!

Good luck, Peter

 

[fire0501]

Re: 1971 Evinrude 60 hp Rebuild.

Wow thanks for that Link I was just about to post and ask how to Hone this Cylinder as I tried it last night and the stones kept catching the ports. They were 4" Stones so I gave up. As far as The melting I believe it was from overheating as The guy I got it from Said he put a new impeller on it but Failed to change the melted housing... Lol at some people. and I believe he may have overheated it that way. #1 cylinder is by far the worst the other 2 are really bad. Its just piston material on the cylinders and I havent been able to find any Gouging or anything yet. The purpose for me to hone was to get the Aluminum off the walls. Glad You gave me that link. I will try this for sure

 

[fire0501]

Re: 1971 Evinrude 60 hp Rebuild.

Looking at my local home depot they only have a Safer Muriatic acid and they reviews stink. Would this work? There are also some Concrete & Mortar Dissolver is that the same thing?

 

[orbanp]

Re: 1971 Evinrude 60 hp Rebuild.

Muriatic acid is hydrochloric acid (HCl). You need HCl to clean off aluminum.
You better get the MSDS sheet to see what actually is in the product. You never know what is in these new environmentally friendly solutions!

Peter

 

[fire0501]

Re: 1971 Evinrude 60 hp Rebuild.

I called a local hardware store they have Muriatic Acid at a 32% For $5 a gallon Im Going to get it right now.

 

[orbanp]

Re: 1971 Evinrude 60 hp Rebuild.

Here is a thread about honing/deglazing: http://forums.iboats.com/mercury-mariner-outboards/hone-deglaze-556659.html
Do a search on iboats, there must be other threads on this as well.
The more you know the better!

Peter

 

[Chinewalker]

Re: 1971 Evinrude 60 hp Rebuild.

Just as an FYI - that logo, the M with the circle around it, was the OMC logo, meaning Johnson/Evinrude-made parts...

 

[fire0501]

Re: 1971 Evinrude 60 hp Rebuild.

Thanks for the info on the Logo. I was starting to think it was an OMC piston but Couldnt find alot of info on it. Thanks for the link I see I need a ball hone. I also did the Muriatic acid last night and after I did that and cleaned all or 95% of the aluminum out I could see that there was some slight Cylinder damage. Unfortunately I think Im just going to sell parts off this Motor and see if I can get another Larger maybe 85hp Motor I hate to give up on any motor but at this point Ill have to bore and buy the ball hone and well you get the point it adds up to more than I want to put into it about 6-$700 which isnt too bad with all the new parts but thats how it goes I guess.