Went to go for an afterwork session yesterday and boat fired up, but the belt was just squealing. Upon further inspection it wasn't moving at all. I had my mechanic take a quick look at it and he simply removed the belt and put some force on the water pump pulley and it freed up. He said somehow the engine made a turn backwards when I shut it down and turned the impeller vanes backwards. He said that it was rare for that to happen on a fuel injected engine. I am so glad it was a free and easy fix. Any of you guys with the Mag MPI 350 have a similar experience and if so are there any preventative measures I can take to keep it from happening again?
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On my old Dodge with a Cummins, one of the pulleys seized and kicked backwards. Snapped every pulley. Luckily it was still under warranty. -
That happened once on our '01 21V RE many years ago. In our case it was time for a new impeller in the water pump. Might be a good indication in your case as well. Ours was the Merc 315 but same water pump and engine, just different fuel injection.Originally posted by hossdog View PostComment
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Yeah, that's what I would of thought accept the impeller in it only has 3-5 hours on it. It also has all new belt, cap, rotor, wires, plugs, fuel filter, oil and oil filter. It was brand new two weeks ago. He said if I've been running it hard to make sure and let it idle for a bit before shutting the engine off. I hope this isn't something that happens often as it was pretty embarrassing with the crazy squeal at the launch with 4 of my buddies ready to go ride and several other audience members waiting to get their boats out at the launch! Another guy I know was there who owns a Malibu and I'll probably catch crap over this for years to come.Comment
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I'll add that when the boat is shut down the impeller is warmer and probably more flexible making the veins easier to reverse direction. When I went to start it they were probably colder and stiffer or the belt probably would have just forced it to go the right direction with minimum squeal. I'm just not sure why the engine would have done a backwards revolution in the first place.Comment
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Originally posted by hossdog View Post
Now that I think about it. We might have had the problem just AFTER we replaced the impeller... I think it was due to not lubing it up enough when we installed the new impeller. If you look at a brand new impeller, the 'oars' are like spokes on a bike wheel, the can be pushed either way. After a bit of use, they lean away from the direction of rotation and it become much harder, if not impossible for them to reverse. On a brand new impeller it may not take a full rotation of the engine for them to flip the wrong way, just a quick stop. I think the problem went away after a bit of break-in. This was at least 5-6 years ago so my memory is a little hazy.
We replaced it every couple of years and I don't recall us having the same issue since we made sure to use way more goop each time after.Comment
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Its a pretty common occurance on a mercruiser. Seen a bunch of them do it.Comment
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Its happened to me just once a few years ago. It killed the belt too, so I would recommend buying one to throw in just in case. I usually have an impeller/housing unit, starter, belt, fuses and jump pack for those situations.Comment
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Seems weird that the belt wouldn't have enough force to just right the impeller, but oh well at least know what to do if it happens again.
Thanks,Comment
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