MARK 55 CLUNKS WHEN SHIFTING

[jrm80]

I DID A RESTORATION ON A MARK 55 AND AS PART OF THE PROCESS, I REMOVED THE LOWER UNIT AND REPLACED THE SEALS, WATER PUMP ETC. NOW THAT IT IS BACK TOGETHER AND RUNNING, I HAVE A CLEAR AND DISTINCT CLUNK WHEN SHIFTING INTO GEAR, EITHER FORWARD OR BACKWARDS. IT IS THE KIND OF CLUNK YOU WOULD EXPECT IF YOU SHIFTED AT TOO HIGH OF AN RPM. . I DON’T HAVE A TACHOMETER, BUT I’M GUESSING MY IDLE SPEED IS 5-600 RPM WHICH SHOULD BE SLOW ENOUGH TO SHIFT WITHOUT ANY PROBLEM. ONCE IN GEAR, THERE IS NO NOISE AND IT PERFORMS PROPERLY AT HIGH AND LOW SPEED. I DOUBLE CHECKED THE GREASE AND FIND THE GREASE LEVEL TO BE CORRECT. THE PROPELLER IS ALSO SNUGLY ATTACHED AND SPINS FREELY. I AM AT A LOSS TO EXPLAIN WHY THERE IS THIS CLUNKING SOUND WHEN SHIFTING AND WOULD APPRECIATE ANY SUGGESTIONS AS TO WHAT MIGHT BE CAUSING IT..

[dave-bernard]

If you have a brass prop it will clunk more then an aluminum prop. do you have oil or grease in it should be grease I use John Deer corn head grease

[jrm80]

THANKS FOR THE REPLY. I DO HAVE A BRASS PROP SO THAT MIGHT EXPLAIN SOME OF IT. I HAVE 105 GREASE IN IT NOW WHICH I’LL BE CHANGING TO CORNHEAD GREASE WHEN THE TIME COMES. THE CORNHEAD GREASE IS MUCH CHEAPER AS YOU KNOW.

SO SHOULD I JUST GET USED TO THE CLUNKING? IT REALLY GIVES ME THE WILLIES HEARING THAT CLUNK AND CONJURES UP VISIONS OF STRIPPED GEARS, DRIVESHAFT SPLINES ETC. I SUPPOSE I COULD TRY AN ALUMINUM PROP AND SEE WHAT THAT SOUNDS LIKE.

ANY HOW, THANKS FOR THE REASSURANCE.

[dave-bernard]

you should be OK see if you can lower the idle.
1 914 310 7086

[frankr]

I thought they all clunk. But they don’t wear out clutch dogs. Much as I hate to admit that.

[billw]

No, they don’t wear out clutch dogs but sometimes they will shatter a clutch dog, if they clunk too much. Clunking is normal to a point; but if I were in that situation and wasn’t exactly sure of the RPM, I would get a tach and check the speed, to BE sure.

Long live American manufacturing!

[fleetwin]

The mercs do “clunk” when shifting normally. Clunking is one thing, but is it “chattering” when shifting into either/both gears? Chattering indicates incomplete/partial engagement and spells trouble. Did you have this engine running with that prop before replacing the seals? If so, how did it clunk prior to servicing?
“Cornhead grease” in this Merc’s lower unit?? I’m not a merc guy, but I wouldn’t use that grease in the gearcase, I would use the usual gear oil that Merc prescribes? You just replaced the seals so leakage shouldn’t be an issue. I will let the Merc guys pass judgement on this…
Again, one “clunk” is normal and OK, chattering spells trouble.

[dave-bernard]

Mercury does NOT prescribe oil in that lower unit. it uses Grease. later jet prop exhaust lowers use oil.

[jrm80]

THANK YOU FOR THE ADDITIONAL COMMENTS. I DON’T USE GEAR OIL IN THE LOWER UNIT, I USE GREASE AS PRESCRIBED BY MERCURY. THE CORNHEAD GREASE IS A SUITABLE SUBSTITUTE FOR THE 105 GREASE THAT IS BECOMING HARDER TO COME BY AND MORE EXPENSIVE AS WELL. IT’S A MOOT POINT THOUGH AS THERE IS 105 GREASE IN IT NOW. I AM NOT EXPERIENCING ANY CHATTERING SO THAT IS NOT AN ISSUE. IT SOUNDS LIKE I’LL JUST HAVE TO GET USED TO THE CLUNKING, BUT I THINK I’LL TRY AN ALUMINUM PROP TO SEE IF THAT HELPS. I ALMOST HOPE NOT AS THE BRASS PROP LOOKS REALLY NICE WHEN IT IS ALL SHINED UP.

THANKS AGAIN FOR THE HELP.

[fleetwin]

OK, thought this engine would use conventional gear lube….

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