1975 mercury 650 rebuild

[jakestevens]

I have the crankshaft and piston assembly inside the block. I noticed that I can wiggle the rod cap a little. I was wondering if anyone knew if this was just a slack tolerance thing or what. I used new needle bearings but used the original cage.

Any help would be appreciated.

thank you
js

[powerabout]

normal
what grease did you use to assemble the big end?

[jakestevens]

I used white lithium grease. It helped keep all of the needle bearing in place.

[powerabout]

You want to make sure you wash it out with some gas as if that grease causes a roller to slide your rod and crank will be toast in 5 minutes.

Next time use vaseline as it washes away in seconds when the engine starts.

[jakestevens]

OK. I understand that. With the white lithium grease not washing away quickly, the needle bearings will slide around the crank rather than roll.
What about the loose feeling of the rod on the crank? Is that normal? There were no signs of wear on the rods or crank at tear down.

[powerabout]

yes the rod to roller to crank pin clearance is not tight enough to make the rod firm so you can move it about also due to the side clearance.
As long as the rollers roll they can stand alot of wear and clearance.
How's the clearance from crank to the reed block, was the crank worn there, was there concentric wear rings on the crank?
The issue there is lack of cylinder to cylinder seal via the labyrinth seal.
Mainly noticeable in poor idling and a bit less get up and go.
Make sure you check the crank end play as well.
best of luck
Powerabout

[powerabout]

on second thoughts it might have bearings in all 3 places?
old age....

[jakestevens]

There was no noticeable wear on the crank at all. Most of the movement I feel is in the side clearance of the rod connection to the crank. So, it seems I can go forward with the build. I will wash with some gas to make sure the needle bearing will roll, and then I'll check the end play. I ordered a shim kit to perform this check.
Should I wash the bearing area at the reed block to crank as well?
Can I just douse the assembly with gas and blow it out with some compressed air while turning the crankshaft?

Thank you very much for this detailed information. It's the best I've gotten so far.

[powerabout]

you need to wash all the lithium away even on the wrist pin bearings as well.
Use anything to get rid of it except toilet cleaner as that will dissolve the aluminium.

[jakestevens]

Thanks for the info. I plan on getting everything washed up tonight.
Do you have any other tips for the remainder of the assembly?

[powerabout]

dont run E10 in it
well if you want ot preserve an old girl,
Make a plate up to go where the powerhead gasket is and pressure test the cooling in the powerhead...a local dealer may have one.
This was not a merc part but as you have a bolted up inner water jacket cover you will not know if it is leaking to not

[jakestevens]

thanks a lot. I finished the crankshaft/piston assembly. When I was ready to install the exhaust manifold cover and baffle plate I discovered that the new block I was building isn't the same configuration as the one I was replacing. The new block is in the serial number range: 3293184 THRU 3525440. And my original block is in the serial number range: 3547987 THRU 4382056. I'm at a stand still until i can find the exhaust cover parts. I appreciate your help up to this point.