dna

Also another dumb question. I know when running the engine on shore that I must have muffs and hose water on at all times because even a few seconds of dry running can damage the rubber impeller. So being that the water pump turns with the crank, does that mean I need muffs and water on when even doing my compression tests being that I'm turning over the engine 4-6 times per cylinder - is this 'dry' turning damaging my impeller.

Thanks

Knot 4 Me

Rotating the engine by hand or bumping the starter dry will not hurt the impeller. Do yourself a favor and buy the Mercury muffs with the wire that passes through the water pickups and won't allow the muffs to fall off and ensures a tight seal.

Warship2k15

Ok on the one the nut was loose.
Are you sure the valve isnt hanging open.
That would cause a loss in compression and a loose rocker.

dna

Not sure yet. Plan to get #5 to tdc after work today and put in 100psi (leak test it) - this should tell me if the valve is tight and also if the ring is OK - I'll provide update once it get this done (might be tomorrow as it has been raining all day so far). But thanks for the suggestion - gives me another possible thing to investigate and look into as I diagnose it alter today.

dna

Have another dumb question.

Still wanting to understand what happens to the exhaust if an exhaust valve is stuck closed (like mine was due to the rocker not able to push the spring/valve open). When I first lost power I did limp it back to my dock - likely ran it for 5 minutes at 2000rpm that way. Since it was getting fuel in and thus combustion, where would the exhaust have gone - can this cause damage in 5 minutes? From the reading I've done, I think it will eventually burn the valve face or head seat. Just wanting to know whether this is a high probability for me by running it for 5 minutes with no exhaust valve opening on #5?

Second, after I figured out there was an issue on my dock (through the compression test showing 50psi on #5), I had to drive it back to the launch. I left the spark plug in #5 but removed the plug wire (thus no spark/combustion). Drove it for about 7 minutes to the launch at 15000rpm that way. Could this have caused more issues? I now guess fuel would have gone into the cylinder, but no combustion would occur and there would be no where for the fuel to go being the exhaust vlave was not opening - what would this cause? Where would the fuel have gone? Would it just fill the cavity between the piston and head and stay there?

Thanks

phragle

iTrader: (3)

At worst excess fuel would wash the cylinder. Think suck bang blow. If you fill your fridge with beer, then chill it but do not take any out to drink, you aren't going to put more in very easily except for maybe replacing a couple that fall out when u open the door.

dereknkathy

It would backfire into intake with plug hooked up. Otherwise it'll just push unburnt charge into intake and suck it back in. This is nothing like running with blown head gasket the way it flame-cut the head.

F-2 Speedy

iTrader: (6)

Sounds like a gal I dated

phragle

iTrader: (3)

Sorry Bro...I think I inadvertently banged your girl.....

dna

OK, did some more work today - there is good news and bad news. Need some good advice.

So in the end I was wrong -- the rocker arm that came off was the intake of #5 (not the exhaust of #5). Either way I reinstalled the nut with proper lash and with the valve cover still off (and the exhaust manifold loose and riser off) I did a new compression test of the 4 cylinders on the right side (1,3,5,7). 1,3,7 were all good and same as before (between 120 and 140). #5 was now at 82psi (was closer to 90 before this new issue occurred). I then removed both intake and exhaust rocker arms on #5 and hit the top of the valves with a rubber hammer (just to make sure it was seated as best as possible) and then introcued 100psi - confirmed no air coming out dipstick (good piston and rings) and no air from intake or carb (good intake valve), but major air coming out exhaust. So the cause of 82 psi is a bad exhaust valve, either it needs to be reground or maybe the valve is burnt.

So my dilemma. I know no 1 cylinder should be under 100psi and no 1 cylinder less than 30% of the higher psi cylinder (30% of 140 is 98). However, after I first installed the heads I only had 90psi on #5 and the boat still ran better than it ever did. Can I leave it for this season with the 1 cylinder at 82? Will/can this cause more damage? There is only another 2 good months of boating here in Calgary and I'd rather be out on the lake versus spending another 2 weeks to do the repair now. I could always save the valve fix for the winter. Your thoughts????

Oh, did some googlin too. Read that some guys put in a shim ontot the bottom of the spring to add more tension/pressure which sometimes causes the valve to reseat or seat better (less leak). Does this sound like a good idea? How bout if I got one of the spare springs from my old damaged head and stretched it half an inch (to add tension). Your thoughts? Again, this would only be a temp fix so I can use it now for the rest fo the season. BTW - realistically, being that the boat primarily would be used during weekends, we are talking like 20 hours or running til end of season.