1977 Evinrude 75 Hp Longshaft Rebuild

[AllanF]

I am rebuilding this motor which has never been apart before. My Father bought it new and it has been used every year.

The machine shop (OCS in Orillia On) have honed the cylinders and said it needed new pistons because the skirts were worn.
I am happy it did not need a rebore.

These motors were used in stock racing with a short shaft and small gearcase.
Part of the crankcase inner passages is coated with brown "glyptal" paint - apparently to slow down heat transfer?
I am not sure if this was only done on the 75HP models???

Anyone have any experience/advice on rebuilding this? I have seen service bulletins on newer models.
Some recommend installing a telltale from the top of the block, increasing jet sizes to compensate for ethanol in the fuel and backing off the timing??
To be fair - the motor has survived on low octane fuel and multiple operators although lately, I insisted on 89 octane fuel and 25:1 oil ratio. Maybe not soon enough to save the pistons

The 3 cylinder motors are some of the best motors ever made. Mr Charles Strang was at OMC during its development.
It is not as easy as taking an old Merc 4 cylinder apart though - lots of pieces

I am familiar with Maxrules site and may ask him the same questions.

Thanks,

Allan

[Locomotion]

You might want to contact Joe McCauley of McCauley and Son Outboard Services in Houston, he is very knowledgeable on these particular engines.

[Fitz73222]

We sold and serviced many of the 3 cylinder versions during the 70's. The brown interior passage coating was called lyfanite, all OMC engines had it in the day to minimize corrosion, which in my opinion worked very well. We were a Florida east coast dealer so everything we sold went to salt life. I can't speak to Stinger/Hustler race engine vurtues, but the stock engines would suffer from broken rings, broken rods (usually Number 1 or 2), and worn labyrinth seals that were machined into the block. So beware, if this engine had idling issues for no apparent reason, being otherwise healhy, the labyrinth seals in the block may be worn for which there is no repair. I did know of a bandade repair that seemed to work by using a set of 1972 65hp carbs, with adjustable low speed jets that allowed you get a better quality idle for an engine that would otherwise be headed to the scrap pile.

[AllanF]

Thanks for the replies. The mechanic who is working on it called it glyptal. Glyptal is also a paint used on electric motors. It is on the passages inside the crankcase and also on the exhaust chamber.
He said something about heat - but I will ask more questions when I pick it up. I am not sure if this was a performance thing used on the 75 HP.
Problem is some of it is dissolving because of overusing Seafoam. Seafoam dissolved the crankcase sealant and made the piston tops really shiny on a Merc 110.

Be very careful when giving instructions to others

Allan