SmurfOnABoat

My engine is a 98 HP500

Ok, well I had a restriction in my cooling system last season and toasted a headgasket on the last outing of the year. Got the boat back to the dock and went home. Did a compression check and found bank 2 cylinders to all be 50psi or less. After tearing down the engine I found the headgasket blown between each cylinder.

I sent the heads to the machine shop, had them magnafluxed, and refreshed. Replaced the headgaskets with 17048 gaskets. New ARP bolts, sealed all the bolts with ARP thread sealant. I did make a switch from the factory Dart intake to a Weiand Team G. Used the Cometic C5649-060 intake gaskets, and trimmed them so the valley pan could fit.

Fired the motor, all was good, took it to the lake, came back and found about 4-5qts of water in the crankcase. (Also noticed a weird whistling sound at certain RPMs) Immediately flushed the engine and got fresh oil in it. First thought was intake gaskets, so I removed the intake, checked the gaskets and reinstalled everything, being more generous with the RTV. Took it out again and low and behold, it leaked again, but only when you actually drive the boat and put more water and pressure through it. Flushed the engine again, put fresh oil in. Removed the oil cooler to take a look at what was going on. Pressure tested to 120psi, no leaks.

I am ready to remove the cylinder heads and see if something went wrong with the head gasket install, but I am at a loss unless the heads and/or block is cracked. Anyone else have any other ideas?

Thunderstruck

Before you tear it down check the exhaust manifolds. Might've cracked when it overheated. I had a hole in exhaust and it filled up the block by pushing the water past the rings. Just a thought, may be an easy fix instead of the teardown.

SmurfOnABoat

Brand new lightning headers with the motor this year....

US1 Fountain

Are you sure the intake is bolted down tight? Recheck the 1st bolt in the torque pattern after you get to the last one. It took me at least 5-6 times around before all bolts held torque. Mine also filled with water till I ran across this issue. Just the 2 times around the pattern wasn't enough in my case.

That much water I can't see an exhaust problem. Motor would hydro lock, I'd think

SmurfOnABoat

I retorqued and then some on the second reseal of the gaskets. No change.

Will not mix at idle, only under higher pressure.

I forgot to mention that its pulling this much water in about 5 minutes of run time.

DareDevil

head gasket or intake !

compedgemarine

did you check the surface of the block? generally when a head gasket goes it damages the head surface and the block surface.

SmurfOnABoat

I did not have the block machined, I left the shortblock alone. I plastigauged the bearings, and installed a new oil pump.

I checked flatness of the deck, and it was .002" max, I was originally going to run MLS, but since I did not have the correct RA, I ran the 17048 gaskets instead.

Even with a bad surface you think it could mix that amount of oil that fast?

Rockfish71

You need to run these intake gaskets you have a intake leak and what you are hearing is a vaccum leak
http://www.cpperformance.com/p-11759...ular-port.aspx

c_deezy

Pressure test the block with water before you take anything apart. You will be able to hear the water going in and where it's going in.

1) Pull the spark plugs out so if it is indeed a head gasket you'll see it dribbling out of the cylinder - doesn't sound likely based on the above
2) Plug the water outlet hoses going to the exhaust
3) Use a garden hose and clamp it to the inlet hose going into the motor, after all the coolers.

I use a ball valve between the garden hose and intake hose to control how much pressure I build, most municipal water pressure is around 40 psi. If you have a water pressure guage that helps.

But then you should be able to tell pretty quick where your leak is. If you do that and it holds pressure, it's something external to the engine.