Major issues with the new boat...help!

[2UNREEL]

I have a 1985 Sea Ray 250. It has a mercruiser 260 FWC. I am going through doing a tune up before I put it back in the water. I am running on ear muffs. The engine sounded good at higher rpm but at low rpm the engine would surge. Occationally off and on I would hear what I would call piston slap or something not firing. I was suspect of the #6 cylinder when I pulled the plugs cause to me it looked like water on the plug along with some oil fowling. So after the new plugs were installed I pulled the #6 plug while running and the engine did not skip a beat. So I pulled the plug and found water on the new plug. I installed new water shutters a few weeks ago cause when I test drove the boat I could hear them slapping the y-pipe. The new shutters I put in seem to be tight fitting and seem to somewhat stick closed. The shutters do not close comepletley either? Could I get water backing up from those shutters into the engine? Or will the pressure from the exhaust blow and keep those open? I sanded the inside of the pipe to allow the shutters to be smoother but they are still somewhat sticky. Also I have evidence of water leakage at the base of my risers? Is this an indicator that the gasket could be shot and I may get water into the exhaust from there? Or do I have my garden hose turned up too much and somehow getting excess water in the engine? On another note it seems like I have what I call steam comming out of my vent tubes from the valve covers to the flame arrestor....Is that normal?........ I am at witts end I need help anything please.... I think my next step is a compression check that I should have done before I bought the boat:confused:

Andy

[Tad Pole]

I would do a compression check to rule out a blown head gasket

[boomerang]

try not so much hose pressure on your ear muffs, remember you boat sitting in the water has NO positive water perssure forcing water into the impeller pump, then you can eliminate that causing that trouble then go from there, for sure you got something bad going on....id bet the high hose perssure is causing it, but i am not a marine mechanic but frank is try calling him... calumet marine...708-862-2407

[2UNREEL]

My father in law came over last night and he is a pretty darn good mechanic. We checked the compression and #6 had 40lbs and #5 on the opposite side had 50lbs. All the rest of the cylinders had 150lbs. We fired the motor up cause he wanted to hear it and he says there is no doubt in his mind that I have a couple of sticky exhaust valves, you can hear the motor at low idle and sometimes they are working and sometimes they are leaking. Also the noise that I am hearing that I thought was piston slap is comming from the new flappers that I put it. They must be sticking occationally, I don't know what to think about those if there in upside down or what. So I suppose I am going to try some magic formula of some kind in a can and run it for a while in the yard and recheck the compression to see if it helps and maybe be able to use it untill I have time to tear down and do a propper valve job. I am going to pull off the exhaust risers and check them cause there is evidence of water around them and replace the gasket, it could be a combo of the flappers and risers letting a tiny bit of water in through a stuck open valve.

[Nailer]

I'm no marine mechanic but, my first guess would be head gasket. How can water get in through the valve?

[GLF]

I'm no marine mechanic but, my first guess would be head gasket. How can water get in through the valve?

I had this problem with one of my engines. The exhaust bellow broke/came off at the lower unit and scooped up a bunch of water. My shutter valves were broken, and I had water in several cylinders.

The valves do not instantly close at the end of the exhaust stroke. If his valves are sticking, its very possible to get water in the cylinder.

I was also told about the garden hose/muffs and water issue.

[2UNREEL]

Last night I pulled the exhaust manifolds and I think that gasket between the riser and the manifold has been been for a while. I belive the water definely came in from the exhaust, just not positve where. I am trying to determine if I need to replace the manifolds and risers or not. While I'm half way there I am going to pull the heads and probbably do a valve job on them just to make sure everythings ok. I still need to determine why I had low compression in the two cylinders. I'll be on the water someday......Hopefully before the next tournament.