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TOPIC: Mercury 800 starting after 20 years

Mercury 800 starting after 20 years 1 year 11 months ago #128211

I have a 61 Mercury 800 engine that has not been started in 20 plus years, It turns freely, and appears in great condition. What Im asking is, is there a way to lubricate bottom end of motor without disassembling it. The motor appears to have very low hours, and lower unit was removed for water pump replacement and never assembled. I have a few other motors that have sit dormant, but not as long as this one. I don't want to destroy the motor, but cant afford to disassemble and inspect it if I don't have to. Any insight on this would be appreciated.

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Re:Mercury 800 starting after 20 years 1 year 11 months ago #128216

Pretty sweet looking 800DR. Is it a long shaft or short??

Pre-lube the cylinder walls with a 25:1 fuel mix via the spark plug holes. Then slowly rotate the flywheel for a few minutes to allow the lube to dissipate. Then do compression tests.
If the compressions check out good,...
You really should lift the powerhead and pull the bottom end cap.
It is pretty common (in my area anyway) that ambient moisture has trickled down over the years and compromised the bottom main bearing.
You can remove the bottom end cap without splitting the crankcase open. Use a common puller, and ease it out.
Don't try to pry it out - you will damage the shims and risk ruining the end cap and/or block surface.
Once the end cap is removed, You will be able to inspect the ball bearing for rust & pitting, etc.
Then heat the end cap with a MAPP gas torch, and the bearing will fall out at about 200*.
Inspect the bearing again, and while it is out, replace the (2) seals and replace the o-ring.
To reinstall the end cap, start with extra long 5/15 NC cap-screws to guide the end cap is straight. Grease the o-ring and O.D. of the end cap. Gently tap the end cap periodically with a soft blow hammer as it goes into the block.

I would also strongly encourage you to pull the flywheel and R&R the top end cap.
When you do,...Be sure and mark the distributor pulley & flywheel using the specific timing marks, before you pull the flywheel.

Just post if you need any insight in any of this stuff.
All the seals, bearings, and o-rings are available.

Once these maintenance updates have been completed, everything else should be external, but if it has been used in salt water, you really should disassemble the port side cover and carefully inspect the baffle plate for corrosion caused breaks down in the deep valleys of the casting.

The attached pictures are of a very well kept, salt free Merc 1000, from eastern Washington state, but still, time takes its toll.

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Re:Mercury 800 starting after 20 years 1 year 11 months ago #128219

Thanks for the info. I don't believe this engine has ever seen salt water. Im in central Kansas and miles from any coast. Having lived in Florida most of my life, Ive seen motors that have been in salt. When I was a kid, My dad bought a new 135 Mercury that had been under water. I watched him pull the crank and pistons out, and then reinstall the assembly down into the block, working the rings in with common hand tools. It was a great motor and we used it for many years. I will take your advice, and pull powerhead, but it may be a while. The motor is a long shaft. Thanks for your help.

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