Clunk Test – – Wrist Pin Test

[Mike Nazarenko]

Just purchased a 1957 Evinrude Sportwin 10 hp and have been reading about the dreaded clunk test to test for wrist pin play. Can someone point me to what and where that test my be in the forum and how it correlates to compression and if the motor is worth repairing.

Thank you.

[Bob Wight]

Rotate the flywheel until the piston is just past top dead center and on it’s down stroke. Insert a wood dowel or screwdriver thru the spark plug hole and push in on the piston. If the wrist pins or rod bushings are worn, you will feel the free play and hear the clunk. A tiny bit of play is probably OK but a big clunk will let you know the engine needs some big work.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

1 user thanked author for this post.

Mike Nazarenko

[olcah]

Sometmes the test can be misleading. Before major disassembly see this thread. If you think there is a problem you can check by removing the exhaust cover and plate.
https://www.aomci.org/forums/topic/connecting-rod-bearings-1956-johnson-30-hp/

[fleetwin]

Well, both points are valid. There will always be a very slight bit of movement due to sideways piston slop against the cylinder. You will know if there is a big problem, you will feel definite movement and hear a clunk. Don’t know if I would pull the exhaust cover though, that is a messy job that usually involves broken fasteners.
Sloppy wrist pins are usually pretty evident when running the engine also…You will hear the clunking at dead idle, will probably dissipate when the throttle is advanced a bit…

[Mike Nazarenko]

Thank you all for the counsel.

I checked yesterday and there is virtually no play when pushing on either cylinders after top dead center on the down stroke, so I won’t fix what doesn’t appear to be broken and prepare it for the water and see how it does.

Thanks again.

[fleetwin]

Sounds like the perfect approach to me…..

[Author]

Posts