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Mercury 150 4 stroke vibration

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sdk8103

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While doing a good deed and towing a boat that ran out of gas, I ran into a problem as we approached the dock. The engine shook and then stalled. It would start and then stall when put into gear. This happened a few times and then I was able to idle to my dock. It was when I raised the engine that I found a line wrapped around my prop. I cut the line off and everything looked fine. Tonight I took it out and I have a slight rough idle even when out of gear, and a vibration when running. I am wondering if maybe I fouled a plug(s) with it stalling and restarting? I am replacing the prop in case it got bent. Any other ideas? It ran like a champ before this incident. Thanks in advance.
 
How fast were you pulling the boat... where was your throttle sitting....1/4, 1/2, more? If you were up around 1/2 or more I'd guess you burned a (hole in) a piston. I had the same thing happen to a friend who loaded his boat with a lot of camping gear and took off on a 40 mile trip doun the Intercoastal Canal in S. Tx. to his fishing cabin. Had he changed propellers to allow the engine to run in its RPM range, he would have gone slower (probably) but wouldn't have burned up his engine. His was a 2 stroke Johnson 125 V4.

But I know nothing (to speak of) about 4 strokers (outboards) per se but you might get a fiber optic scope and remove your spark plugs and have a look at the top of your pistons.
 
Texasmark said:
How fast were you pulling the boat... where was your throttle sitting....1/4, 1/2, more? If you were up around 1/2 or more I'd guess you burned a (hole in) a piston. I had the same thing happen to a friend who loaded his boat with a lot of camping gear and took off on a 40 mile trip doun the Intercoastal Canal in S. Tx. to his fishing cabin. Had he changed propellers to allow the engine to run in its RPM range, he would have gone slower (probably) but wouldn't have burned up his engine. His was a 2 stroke Johnson 125 V4.

But I know nothing (to speak of) about 4 strokers (outboards) per se but you might get a fiber optic scope and remove your spark plugs and have a look at the top of your pistons.
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Just idle speed. It only happened after snagging the line so it had nothing to do with the tow.
 
I would say that you have a wad of material wrapped around your prop shaft behind the prop but you said it does it in N also which negates that thought. Pulling the prop off to change props is a good idea to check for debris anyway. A lot of times, especially when fishing places that are popular you will pickup discarded fishing line which will wrap around the prop shaft and can mess up the LU shaft seal. I pull my prop off periodically to check for this as I have had that event happen to me.
 
Texasmark said:
I would say that you have a wad of material wrapped around your prop shaft behind the prop but you said it does it in N also which negates that thought. Pulling the prop off to change props is a good idea to check for debris anyway. A lot of times, especially when fishing places that are popular you will pickup discarded fishing line which will wrap around the prop shaft and can mess up the LU shaft seal. I pull my prop off periodically to check for this as I have had that event happen to me.
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I bought a new prop thinking maybe it got bent and I wanted a spare anyway, so I had the prop off and there was nothing on the shaft. I also changed the plugs thinking maybe they got fouled, which was a long shot, but worth a shot, but no change.
 
sdk8103 said:
I bought a new prop thinking maybe it got bent and I wanted a spare anyway, so I had the prop off and there was nothing on the shaft. I also changed the plugs thinking maybe they got fouled, which was a long shot, but worth a shot, but no change.
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Positive attitude. Sometimes you just happen upon a fix to a complicated problem. I just had an occurrence yesterday.
 
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