TOPIC: Mark78 Running Issues

Today it sounds like it's running good but yesterday in the water it sounded like crap. Isn't water supposed to come out of the exhaust hole top of midsection?? I'm going to post another one at idle waiting to run the gas out and I hear clunking and clanking. Don't know if that's a normal sound..

Joe place your hand on the exhaust cover(portside)
you should be able to leave your hand there while motor running and not feel uncomfortable to touch, they dont get that hot

I still say that while you were putting along at head way speed you picked something up and when you went to throttle up you were already overheated. This happened to me with my Mark 30 years ago. You may have shaken off the lower unit the bag or whatever may have been obstructing the water intake. It also could be that your impeller was on its way out anyway. When was the last time it was changed? You should see a good amount of water coming out of the exhaust and pee hole if that motor has a pee hole.

Yep def check the exhaust cover it should stay cool or just warm to the touch. Remember water muffs can "help" a bad impeller or duck valves. So if it gets by on the muffs(your flush attch.) it may fail and get hot on the water.

Conrad

What would it be if the water isn't flowing from exhaust? The impeller was changed a couple of years ago when it was pulled out of storage and doesn't have many hours since then. thx,joe

I am not sure if the dock bashers take different impellers or not but I would assume starting in clockwise motion and then counter clockwise it does not take much to wear them out. Shorter lifespan than an impeller that only rotates clockwise.

I would assume starting in clockwise motion and then counter clockwise it does not take much to wear them out. Shorter lifespan than an impeller that only rotates clockwise.

Especially if sitting for any length of time as yours has, they get a set in the blades.whether you used it or not doesnt stop the rubber from aging

There is also a tell tale hole on the left side of the motor (facing fwd from behind motor) It is a small hole right in the top of the leg before it meets the lower belly pan. They normally all get plugged and are hard to get open again with out taking the pwerhead off. Try a long wire and work it around in that hole.

Do the temp check by putting your hand ont he exhaust cavity. But also you can take the top cowl off. There is I believe a small plug on the top of the water cavity, on top of the block. It usually has a big flat screwdriver slot to get it out. If you have that, take it out and run it. you should get water pumping out the top of there if the pump is good. Check it like this in a barrel or on the lake.


Conrad

That rattling ( clunking, clanging ), doesn't sound good to me. Most likely you blew out the vital duckbill ( forward ), or, you may have taken out the key for the impeller, or the bushing has spun. Start it in reverse and see if it pumps water, if it does, the forward duckbill is bad. But, I fear you may have hurt the powerhead with all that noise........sorry, don't shoot the meesenger.....

I'm going to go out and check it out and reverse and it definitely Doesn't piss out the side like yours!!!

Keep us posted Joe! I definately prefer the cav plate attachment I'm using over the screw in type you're using. You're still gonna have to change that impeller though if it ran dry. I just pray, for your sake, you didn't hurt the powerhead! Let us know......

JS

Thanks, went out and started in reverse and not pissin'out the side and maybe a little better out of exhaust. Stays cool, can hold my hand on it even after running awhile. The clanging is coming from L/U, pronounced when stopping.I tried running a trailer wire through that hole on side, no luck. when I drop l/u will I be able to clear that line?? Thx, Joe