MerCruiser 3.0 - loud metal noise when in gear

Bomber2

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Jan 12, 2023
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We took our boat out last week and noticed that when we put it in gear a rattling noise started in the engine and the boat began to vibrate pretty bad at high rpm. Noise sounds like something loose and it’s rattling around - maybe a bearing or rod.

- Haven’t hit the prop on anything
- Replaced the impeller water pump on return - no metal found in the gear oil
- sounds normal when in neutral

Only other issue I have had with it was the trip before last - cable on starter motor broke off so we had to jump it a couple of times to get it back to trailer

Does anyone have any ideas on what it could be or had similar issues.
 

stresspoint

Lieutenant Junior Grade
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Sep 19, 2022
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1,045
remove the drive and see if the noise goes away , to get water to the motor stuff the garden hose into the hole where the rubber O ring is .

iv had a drive plate bolt break and it was rattling around in the bell housing that mad a weird noise.
 

alldodge

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when we put it in gear a rattling noise started in the engine and the boat began to vibrate pretty bad at high rpm.

I'm thinking something in the lower section of the drive. Spin and wiggle the prop (motor off in neutral), is should be quite and no wiggle
 

Bomber2

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Jan 12, 2023
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We took our boat out last week and noticed that when we put it in gear a rattling noise started in the engine and the boat began to vibrate pretty bad at high rpm. Noise sounds like something loose and it’s rattling around - maybe a bearing or rod.

- Haven’t hit the prop on anything
- Replaced the impeller water pump on return - no metal found in the gear oil
- sounds normal when in neutral

Only other issue I have had with it was the trip before last - cable on starter motor broke off so we had to jump it a couple of times to get it back to trailer

Does anyone have any ideas on what it could be or had similar issues.

Thanks for the info - i will do each of these things this weekend
 

Bomber2

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Jan 12, 2023
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Found the problem

We have water in the bellows, U joint rusted and ceased and gimble bearing blown and the bearings have destroyed what i think is the housing.

I wasn't able to pull the bell housing off as i need to get a hinge pin tool but just wondering if the damaged part in image can be fixed without removing the engine?

325618194_2053332105056320_6057924455183787449_n.jpg
 

flashback

Captain
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Jun 28, 2002
Messages
3,963
Try to get the rest of the bearing out of the gimbal housing and check the splines condition in the coupler.
 

dubs283

Vice Admiral
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Jul 27, 2005
Messages
5,322
Flange on the right side of pic is broken off. That is the sealing surface for the u joint bellows. I've never seen one repaired, only choice is to r and r gimbal housing which requires engine removal
 

Lou C

Supreme Mariner
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Nov 10, 2002
Messages
12,654
Yep that flange is what seals the bellows, so you need a new or used gimble housing. That is the Achilles heel of I/Os. The drive needs to be pulled at the end of each season to check the bellows for water, so you can fix it when it's still a small problem, way before it becomes a BIG problem.
 

stresspoint

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Sep 19, 2022
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some sikaflex 5200 , sheel be right mate.

that looks like a nasty mess.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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49,540
Sika makes Sikaflex

3M makes 5200

3M and Sika are two different companies

neither will repair the broken aluminum.
 

stresspoint

Lieutenant Junior Grade
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ome sikaflex 5200 , sheel be right mate.s

that looks like a nasty mess.
same stuff , different bucket .

ok seeing as Op wont be able to use 5200 :eek: , maybe , just some spit and angle grinder with 24 grit ,buff it up and stick a bit of bondo on the ring to hold it in place.

in other words , Op needs to discard the element that is chopped up ( IE: the gimble housing ) and get another one ,there is no point trying to fix that mess no matter what you use .. the result will be the same.
 
Last edited:

Bomber2

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Jan 12, 2023
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4
Found a new housing which we will be putting in

Safe to say the service history that came with the boat is dodgy- doubt anything has been changed or serviced.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
12,654
And all this could have been prevented with yearly maint. SAD
Like I said. Do I always feel like dragging out the outdrive jack at the end of the season, not always but I DO It!
20 years salt water mooring & no major problems with a 1988 OMC Cobra.
 
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