Merc 400 teardown looming

[JEFF POLLACK]

Greetings corona boaters,

I have a 1960 Mercury Kiekhaefer 400 Super Thunderbolt, Model ‘M’ that is ready for an overhaul. I lost most of the water pump impeller last summer, and the motor got pretty hot on me. I got out my compression test gauge, and where I previously had 125 – 130 PSI on all four cylinders, my two middle cylinders are now between 70 & 80 PSI.
I am questioning the logic of diving into a teardown on this 60 year old motor that [was] in otherwise great condition. Considering the expense and availability of parts for this unit.
I would ask if there are any vintage Merc repair enthusiasts that would take on such a task, or assist me with such an overhaul in the Western Washington State region?
Any suggestions or recommendations from seasoned Kiekhaefer buffs would be welcome.

Thanks,

Jeff Pollack
jspchlosky@outlook.com
Kingston, Washington

• This topic was modified 3 years, 11 months ago by Mumbles.

[billw]

Well I am on Cape Cod, in Massachusetts, so that leaves ME out! Number one, if it’s ever seen salt water, forgiddaboutit. If strictly fresh water, then how is the gear case condition? Do you religiously check and change the gear oil/grease? If not, I would hate to see you do a power head, only to loose the lower unit soon after. Old Mercs are notorious for that! If you’re still with me to this point, You would need a set of special piston ring compressors to reassemble the power head. However, if you have or somehow obtain, those ring compressors, then the actual job of re-ringing a Merc power head is actually pretty EASY. If the pistons are scored, you can try to get good or new replacements….or just clean them up and use them again. It depends on how bad they are. In the real world, pistons do not have to be as absolutely perfect as many make them out to be, especially in two-stroke applications. What you do need is good, free-moving piston rings and good cylinder walls. The latter will be an unknown until you take it apart and look.

Long live American manufacturing!

• This reply was modified 3 years, 11 months ago by billw.

[fleetwin]

I’m not a merc guy, but that is a beauty… Hopefully a merc guy will weigh in, would be a shame to give up on this engine. Normally, I would recommend pulling the head and having a look, but I know the head is not removeable… When you say you lost the impeller, does that mean the blades broke off? If so, did you find all the pieces? If so, I would be inclined to replace the water pump and get the engine running. The overheat may have just left the engine real dry, perhaps the compression will come up after running with some extra oil in the mix…. This might be wishful thinking, but worth a try….

[A Hoskins]

I, as well, am nowhere near you but can offer this: You do not need to take the engine apart to asses the damage. On the starboard side of the block you can remove the intake port covers to look at the pistons and cylinder walls. If a piston is scored, rotate the crank to put the piston at the bottom of its’ stroke and look through to the other side of the cylinder with a flashlight. Scored walls are a real minus while scored pistons are replaceable. You do not need the special ring compressor. It makes the job easier but the job can be done by hand, carefully, patiently and with a buddy to help. Hopefully someone close to you will chime in and you’ll fine a seasoned technician. Good luck.

"Fox News" isn't.

[billw]

A Hoskins wrote:

I, as well, am nowhere near you but can offer this: You do not need to take the engine apart to asses the damage. On the starboard side of the block you can remove the intake port covers to look at the pistons and cylinder walls. If a piston is scored, rotate the crank to put the piston at the bottom of its’ stroke and look through to the other side of the cylinder with a flashlight. Scored walls are a real minus while scored pistons are replaceable. You do not need the special ring compressor. It makes the job easier but the job can be done by hand, carefully, patiently and with a buddy to help. Hopefully someone close to you will chime in and you’ll fine a seasoned technician. Good luck.

You may not “NEED” a special ring compressor set but you will NEED a number of cocktails, after busting a couple of rings off.

Long live American manufacturing!

[fleetwin]

A Hoskins wrote:

I, as well, am nowhere near you but can offer this: You do not need to take the engine apart to asses the damage. On the starboard side of the block you can remove the intake port covers to look at the pistons and cylinder walls. If a piston is scored, rotate the crank to put the piston at the bottom of its’ stroke and look through to the other side of the cylinder with a flashlight. Scored walls are a real minus while scored pistons are replaceable. You do not need the special ring compressor. It makes the job easier but the job can be done by hand, carefully, patiently and with a buddy to help. Hopefully someone close to you will chime in and you’ll fine a seasoned technician. Good luck.

Good point! Forgot about those little bypass covers….

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