Vibration knocking timing out??

Boat600

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Mar 5, 2015
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So after having carbs cleaned and new thermostat. Took the boat out was running sweet. Way back run poorly and doesn't want to start.

Mechanic says vibration has caused fly wheel to move knocking timing out :(

Paying 8hrs labour now to get timing done but what's the likely hood it could happen again?

On test run it briefy made a fan belt type of noise but then that went.
 

GA_Boater

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May 24, 2011
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Well yes and no.

The NO part - You don't say what Merc you're using to pay for the mechanics' kids college, but I had a similar problem with the Merc 500 in my sig. The timing started jumping because the brand new belt was jumping teeth on the magneto pulley. Turns out the upper magneto bearing went notchy and locking up intermittently and when the mag locked, the path of least resistance was for the belt to jump teeth, throw off the timing and stop the motor.

The YES part - I'm sure the bad bearing caused some undetectable vibration.

Using a Clymers, screwdriver and large hammer*, it didn't take me 8 hours to fix. After waiting a coupla days for two (changed both) bearings to arrive and reassembling, she runs like a top. This was over two years ago.



* Only finest, precision tools were used, but I did use a Clymers. :smile:
 

Boat600

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Mar 5, 2015
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Thanks for the reply it's a Mercury 75hp 2 stroke 99.
The mechanics charging me 8hrs work to retime the engine.
Is it likely they didn't put something in properly? Or another problem that's going to make it happen again :/

I'm on the verge of given up :(

Spent so much an still don't have a running boat
 

racerone

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Dec 28, 2013
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It was mentioned to find another mechanic !!!!!---------It does not take 8 hrs to correct a timing flaw !!!!
 

Boat600

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Mar 5, 2015
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Just canceled with the mechanic! Get some one else on the job. Cheers.
How long do u say it would take?
 

racerone

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Nobody here is standing beside your motor so it is difficult to say what is wrong with your motor.---Posting more info will help.----Start with a compression test.
 
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mr 88

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Should take about a hour,max, if performed by a real mechanic.. Flywheels bolts are installed with locktite/lock washers/bolts peened at the end so they don't back out. I have never seen one move because of vibration,jump a tooth yes.
 

racerone

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I believe these motors have a 1 piece flywheel no bolts to hold a flex plate.------This motor does not have a belt driven distributor.----Therefor it can not ---" jump a tooth " either.
 
Last edited:

GA_Boater

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I believe these motors have a 1 piece flywheel no bolts to hold a flex plate.------This motor does not have a belt driven distributor.----Therefor it can not ---" jump a tooth " either.

Agreed. But it took 2 days to find out what motor.
 

Boat600

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Mar 5, 2015
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Thanks appreciate it.
Fingers crossed it's nothing too bad.
And thanks for guiding me away from the rip off mechanics
 

1nebel0

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Nov 28, 2005
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512
I always index the flywheel to make sure the pointer is set correctly...Sorry don't trust more marine mechanics.. Had a Mac Tool business and called on them and watch the many guys at work...Just got a motor from a buddy for my mini boat...got it out of the shop 3 times and gave up on it buying two brand new ETEC's.. I checked the index which was off...Then did the lync and Sync and found out why it wouldn't start and idle...The carb plates were not closed and lastly, the roller between the bracket that opens the carbs didn't have the necessary gap needed...This was from a reputuable shop..that is why i learned to do everything myself.
 

Boat600

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Mar 5, 2015
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Update ---
New mechanic saw straight away the engine has never had a new fuel fillers and it was the fuel diafram flooding the carbs. No more that ?150 fix.

Thanks so much for all your advice :)

I'd love the kick the other Cowboys arse
 

GA_Boater

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Thanks for the update, Boat600. Make sure you tell other boaters you found a decent boat mechanic. Have fun on the water!
 
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