2008 mercury 50 ELPTO 2 stroke

Hey everyone just looking for some opinions on my motor. I just bought a 2009 bass tracker pro team with a 08 50hp 2 stroke. It has a knock I didn’t notice when I purchased the boat. Starts fine runs perfect just has a slight knock at idle and low rpm goes away at 1500-2000 rpm or just can’t hear it. It sounds like it’s comming from the mid section of the motor if I put my stethoscope on the mid section it’s loud. I checked the top end for rod play and piston slap with the wooden down everything seems to be tight to play in the flywheel as i push pull try to get play out of the crank. The motor looks like it’s brand new and very well maintained not a scratch or stain on it looks like a 2016 which I know doesn’t mean alot. I’d say very low hours. I’m just wondering if anyone has an opinion on what it could be. Does it neutral reverse forward doesn’t matter. At mid to full throttle just seems to quiet to be top end. Is there anything in the midsection that could cause a knock. It’s slight not a hammering. And more of a slow knock not racing fast. I also noticed it has a brand new prop and skegs missing a small piece.

The new prop and piece of skeg missing might indicate a hard strike on the lower unit - may have bent the propshaft or buggered up some of the guts. I would rule that out before moving on to engine mechanical possibilities...

I should mention Its not a loud tick or hammering just noticeable it may just be normal I’ve had a few people say sounds like a 2 stroke

What Graham said. So, if the skeg has a piece out of it, maybe there was a hit and does it really have a new prop? I've dinged many props in my life and had them repaired to look like new; however, there was never a repaired one that was in balance and thus producing vibration that wore out the seals and bearings. To see if it is lower unit or engine, can you put your stethoscope on the lower unit? I learned the hard way to always have a new spare prop and never run a damaged or repaired one.

Yes it is a new prop I will get some pictures and post them up tomorrow. I put my stethoscope on the mid section and it’s the loudest just above the cavitation plate. You can hear a little in the powerhead but I’d say it’s traveling I can get a video also. I put my borescope in all the cylinders and tested again for any piston slap everything looks a1 and tight in the powerhead.

Is there any water in the gear lube in the lower unit and is the lower unit full??? If repair is needed on the lower unit, I know that takes a bunch of special tools and shims, but, I think good marine mechanics would have that. If water - then bad seals; if no water and lubricant is low, you need to get the right Merc gear lube to fill it and also a pump to pump the fluid from the lube container to the bottom of the unit up to the vent screw.

Heres here’s a video at idle and wot works great other than the noise at idle.


[video]https://m.youtube.com/watch?feature=youtu.be&v=AgeCrGe-phs[/video]


[video]https://m.youtube.com/watch?feature=youtu.be&v=GZXzTLtqlwg[/video]

Sounds normal to me.

Jeff

I have a 1992 Merc 40 4 cylinder 2 stroke; when it does idle, the only sound coming out of it is normal exhaust noise. It does not have a clatter like yours; can't tell from your video where that clatter is coming from; but maybe as Jeff above said, that is normal for that year model. I have had other 2 stroke outboards 1956 Johnson and 1968 Evinrude that made no such clatter. Had a Merc 233 drivetrain and lower unit in my 24 foot Searay, no such clatter. Tough decisions to make.

Be nice if it was normal but I’d say it’s definitely in the lower. I’m have to order a water pump kit and remove lower and then start it see if it goes away. Maybe someone else with the same motor may chime in. Thanks for the feedback guys

I've replaced the water pump in the lower unit on my Merc 233 lower - not hard to do - just have to get the rubber impeller wings twisted in the right direction - don't remember how I did that. There isn't much in the water pump - curious to see what you find. On the 233, I had to put the throttle lever into forward to drop the lower unit - don't know if that is necessary now.

If you are replacing the water pump, are you having cooling problems??

Update: I dropped the lower to change the impeller. Everything in the lower was fine I started the motor with the lower off and the noise still existed. I checked the powerhead over again. Flywheel is tight no loose parts. I did the wooden dowl test on the pistons rods everything is tight. Looked inside with a borescope and cylinders look perfect. Am I going nuts haha. I don’t know if I should just order a powerhead from merc or just drive it until it gives up may go for a while may be normal.