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piston ring compressor needed?

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dalefan4lyf

Member
I am rebuilding a 95` 4 cyl 40hp outboard. I need some help with the piston rings. I am not wanting to pat $250 for a set of Mercury piston ring compressors. Any tricks to getting the pistons back in the block without killing the rings?

Thanks in advance!
 
Luckily you have the "broken cap" rods, you can install each piston separately and use your fingers to squeeze ring to allow it to slip into cylinder.
 
Correct , on the newer motors the different technique can be used.-------------You must work carefully to install those " fractured " caps !!
 
That's how I do it as well. Here's the drill:

1. Using spray paint, color each rod and cap a different color on one side ONLY. That not only keeps from mixing them up, it garantees that the cap is on the correct way (which is hard to see on the later rods).

2. Install the pistons, pushing them all the way in and then greasing the rod bearings in place.

3. Put the crank in and attach the center rods first, followed by the outside rods. Keep careful track of the needles to be DAMN sure none of them drop in without you seeing it.

4. The last and most important step of all: Using a pick, poke at the rod bearings, rotating them around the journal to ensure all of the needles are there. Sometimes this will require rinsing the grease out with lacquer thinner (AKA cut finder).

Jeff
 
Here's what I used to do on an auto engine. Cut the top and bottom from a tin can which leaves a tin cylinder. Cut the cylinder end to end to open it up. Wrap it over the piston and rings, wrap a string around the tin can and tighten the string to squeeze the rings. Then tap the piston into the cylinder.
 
The outboard in question is built a little different ( pistons go in from the bottom ) and there are pins in the ring grooves to keep rings from catching on the ports.-----------Not the same as an automotive engine.
 
Did my first inline 6 with 2 pulleys over the workbench, crank assembly hanging on cord with a cinder block counterweight. Worked the rings in one at a time. After that we went out and got some ring squeezers.
 
UPDATE: Got my rebuild kit. Installed the new pistons on the connecting rods. Found that with alot of fogging oil and some patience the pistons went in without tools. The top of the cylinder is machined with a tapper in it. It was very easy to work the pistons into the cylinder. At least one thing went easy so far!
 
Good for you!

Jeff

PS: Those car only motorheads would learn a few new words if they ever did a Merc outboard!
 
Oh, I learned a few new words along the way. I am a gearhead at heart so this boat stuff is a real challenge. This may be a new addiction though.....
 
..."All four letter word are those the ones your talking about or the bigger ones with two or more syllables. "

All of the above--and more!

..."I am a gearhead at heart so this boat stuff is a real challenge. This may be a new addiction though....."

Careful! It quickly bercomes a lifetime obsession.

Jeff
 
"I am a gearhead at heart so this boat stuff is a real challenge. This may be a new addiction though....."
And there ain't no addiction clinics for this disease... yet..:D
 
Have a Mercury 1150 looking for the ring compressors to fit my motor nobody can tell me where to get them new or used they can't even provide me with a serail number can any of you please help thank you for your time
 
I bought a cheap ring compressor and cut it into strips and used large hose clamps just deburred the edges with emery cloth once the piston slips into the cyl you inscrew the hose clamp and waa laa.
 
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