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1977 Evinrude 75 Hp Rebuild

F

FooLingToo

New member
I am rebuilding this motor. It was bought new and has never been rebuilt.
Thanks to GGMurray's post "Powerhead Rebuild or Not" and the great help from people on this board for all the info.

I have it completely disassembled. The block was taken to a machine shop and only required honing the cylinders.
They were surprised it did not need boring - but was on spec with honing.
A kit from WSM with new pistons, all the gaskets, and bearings.
These kits are excellent, great parts and well organized (no instructions though).

Here are some questions I have:

On the block, the crankcase and transfer ports were painted with a brown paint.
This was also used in the water jackets. I was told this was Glyptal paint - which is also used on electric motors.
Why was it used inside the crankcase / ports??
Excessive use of Seafoam (used too long and used before storage) has loosened most of it and I will remove the rest.
Was it a "speed secret" to gain some hp??

The WSM Head Gasket is glossy - do I use gasket sealant on it (not near cylinders)?
The Cylinder head has water jackets on both sides - just sealant where it touches the head and block??

The connecting rods are in good shape and I have practiced matching the caps - no problem so far.
The top cylinder connecting rod bolts were looser than the other two cylinders - but still tight.
OMC says just lubricate with oil and tighten. Would you recommend Loctite instead?

Maxrules build suggestions (on website) recommends red loctite on the mains bolts.
Permatex has a yellow "in between red and blue" threadlocker. I never used red before - so no idea how difficult it is
to disassemble parts after using it... Though I would use the Yellow stuff.

Overall, the motor is in great shape - some bearings were getting noisy and looked like the head gasket might have leaked soon.

Any advice is greatly appreciated. I will also reread GGMurray's post.

I can't believe how many bolts and parts there are to this motor!
Not your simple old 4 cyl Merc!!

Allan

PS: Sorry for not posting pics now. I am at the cottage in The Kawartha Lakes, Ontario Cda.
Have to use the Library"s WiFi!
 
The WSM Head Gasket is glossy - do I use gasket sealant on it (not near cylinders)?
Click to expand...
No sealer required as gasket is silicon impregnated, it will need a retorque when hot. Rod bolts use oil only as previously posted and torque in 3 steps(ie:10-20-30lbs). Use only oil on crankcase bolts and mains,. Chase and clean all bolts and theads before reassembly. It will take about 2.5 hrs to prep block ,bolts and rods. Wash the cylinders, ports and exhaust with warmsoapy water and rinse. Wipe with a white heavy shop towel, if any grey residue (honing debris) rewash till its gone
 
Thanks for the information. I will oil the rod bolts and no sealant on head gasket.;)
I bought a rethreader kit and have cleaned all the bolts and threaded holes.

I have almost finished surfacing the head.
Will resurface cylinder block deck as well.

Removing old gasket material has been time consuming. I have tried Lacquer Thinner which works well.

It also removes the "brown paint" inside the transfer ports and the block crankcase half.
I have to be careful with the Lacquer Thinner as the water jackets are also coated with it.

I am not sure when OMC stopped painting the water jackets or why they painted the ports and half crankcase??

How can I obtain any Service Bulletins for this motor??
I intend to install a "telltale" on the top of the block. Also would like to increase the jet sizes. Any Suggestions??

This is a long shaft motor used for pleasure boating.

Some have stated that the carburetor butterfly shafts wear and cause a lean condition. I am not there yet - but the shafts for the
Choke butterflies were always very sloppy.

I think the motor has been idled alot- I have tried to convince people that this is NOT A FISHING MOTOR!!

It has held up well over the years considering how many people use it.

Thanks,

Allan
 

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There is no need to move the tell tale.----That applied to the 56 cube blocks of 1986 and newer.----I use a carbide scraper to clean gasket surfaces.----You did chamfer the intake and exhaust ports ?
 
Hate to comment on someones work but, thats a chitty hone job not even a good crosshatch. Looks like someone slapped a spring hone in cylinders and just de glazed. A good crosshatch looks like below. Also looks like cylinders are out of round as hone didnt touch bridges in cylinders 1 and 2 as left a shadow from no contact.
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Sorry - the block pics were just to show the deck surface and the "Paint" in the transfer ports and the crankcase half.
I will clean it up after the paint is removed.


I think the hone job is ok - just my bad photo and need for cleaning. I will take a closer look though.
I have not chamfered the ports - I was considering buying a Flex Hone to debur them and as a final step in the honing process.
Any comments?
The Transfer holes in the pistons are very sharp, on both the old and new pistons. It surprised me how sharp the edges are...

There is no tell tale on these motors, water will shoot out the exhaust relief only when the thermostat opens.
I prefer to install a teltale on the top of the block to help purge any air trapped there. There is a large welch plug on the top, so I cannot install
it directly above the cylinder.
There was lime build up above the top cylinder - and also sand/silt in the water jacket.
The lake is getting shallower all the time:(
On the old Mercs I work on, the teltale water is from before the water enters the block.
Not a good indicator of flow thru the motor,
I was not able to upload a pic of the head. I will try again and will look for better pics of the block. My phone had crashed and may have lost them.

Thanks for your comments.

Allan
 

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I have sanded the head already on plate glass but it needs some more to flatten the area around the combustion chambers.

I am going to call the Company that did the honing about chamfering the ports and doing a flex hone treatment.

Just to clarify things, the block was not rebored but was honed to fit standard sized pistons. There are areas that did
not clean up completely but I consider it acceptable versus honing it larger and getting greater piston to cyl clearance.
The pistons have a tight '005" clearance. Evinrude specs say max of .0055".
A rigid hone was definitely used and the company that did the work has a good reputation.

I am busy with other duties at the cottage, but will report back when I start working on it again.
Right now, there is a 1964 Merc 110 (9.8 Hp) waiting for final assembly.
Again, thanks for your comments.

Allan
 
The shadows you see on the bridges, in ports that hone didn't touch shows cylinder/s are slightly out of round. This is areas the rings will not touch unless cylinder is bored. Yes engine will run as it is but may have some slight idling issues.
 
A ball hone leaves a wonderful looking finish.---Follows all the irregularities.------The pistons and rings need a round cylinder with no egg shape / taper or irregular wear.
 
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