Water on top of pistons and rockers

[jeremiah89]

I have a 1991 Renken Seamaster 2688 with a OMC 350. My motor hydrolocks only while in water. It doesn't do it on muffs. I am getting water on both sides of the motor when i pull the plugs snd spin it over. The rocker box on both sides are milky but the oil in the pan is clean. It may be do it 10 minutes on the lake or 3 hrs just depends. The most recent time i was idling and the boat started missing bad until it stalled. I pulled all the plugs and water was on both sides. I took it to a buddy he thinks head gaskets, the motor hasn't been overheated since I've had it the motor has 82hrs on it. I'm not sure if it's risers/manifolds, head gaskets, cracked heads. Any help would be greatly appreciated.

 

[Lou C]

Are the exhaust flappers intact and installed correctly?
Do you see any leaks around the joint between the exhaust elbow and the exhaust manifold?
does this boat sit very low in the stern? You need 13-14" between the static water line and the tops of the exhaust elbows to prevent water from spilling over into the cylinders.
A blown HG can let water in but usually it won't be all the cyls, maybe one on one side, depending on where its blown. I had this on mine 3 years after an overheat.
I might pull the boat out, remove the exhaust manifold/elbow as a unit and test them. Prop it up level hook up a water hose to the inlet and run water through it for a while then shut it off, see if any water drips down to the exhaust ports that mate up with the cyl head exhaust ports.
If they pass, then you have to go further. There is a way to check for bad head gaskets, what you do is replace the manifold feed hoses with clear hose. Put the boat in the water and run it till the engine warms up, and the thermostat opens (160-165* on the gauge) get someone to run the engine above idle speed, and see if you see air bubbles in the water flow out of the thermostat housing to the manifolds, if so that's a sign of a blown HG or cracked head. Exhaust gas getting into the cooling water. To pull the heads on one of these is not a bad job especially if it was used in fresh water. Usually with overheat damage on a Chevy small block the heads can crack and/or damage the head gasket but the block should be OK.

Was the boat always winterized properly? Cracks can certainly be a result of bad winterization practices too.

 

[vasy]

Good Spam to start off a year? (2nd post)

 

[jeremiah89]

Are the exhaust flappers intact and installed correctly?
Do you see any leaks around the joint between the exhaust elbow and the exhaust manifold?
does this boat sit very low in the stern? You need 13-14" between the static water line and the tops of the exhaust elbows to prevent water from spilling over into the cylinders.
A blown HG can let water in but usually it won't be all the cyls, maybe one on one side, depending on where its blown. I had this on mine 3 years after an overheat.
I might pull the boat out, remove the exhaust manifold/elbow as a unit and test them. Prop it up level hook up a water hose to the inlet and run water through it for a while then shut it off, see if any water drips down to the exhaust ports that mate up with the cyl head exhaust ports.
If they pass, then you have to go further. There is a way to check for bad head gaskets, what you do is replace the manifold feed hoses with clear hose. Put the boat in the water and run it till the engine warms up, and the thermostat opens (160-165* on the gauge) get someone to run the engine above idle speed, and see if you see air bubbles in the water flow out of the thermostat housing to the manifolds, if so that's a sign of a blown HG or cracked head. Exhaust gas getting into the cooling water. To pull the heads on one of these is not a bad job especially if it was used in fresh water. Usually with overheat damage on a Chevy small block the heads can crack and/or damage the head gasket but the block should be OK.

Was the boat always winterized properly? Cracks can certainly be a result of bad winterization practices too.

I was thinking exhaust flappers also but Renken stopped putting them on this year model boat on 91 atleast from the research i did.

 

[Scott Danforth]

first, welcome aboard

second, pull the manifolds and acetone test them for leaks and pressure test your water jacket

third, if they pass, measure your riser to SWL. being a 30 year old boat, if your heavy with water, you may be less than the 14" recommended.

 

[Lou C]

I was thinking exhaust flappers also but Renken stopped putting them on this year model boat on 91 atleast from the research i did.

The flapper would have been installed in the Y pipe by OMC at the factory, I doubt Renken or any boat company would have changed what the factory set up on their sterndrive packages.

EXHAUST & COOLING - 1991 OMC Stern Drive 5.7 574BPERGD | Crowley Marine

part # 32, just like all the first run OMC Cobras. Volvo removed them from '99 on the SX series, but I don't think that was a good decision.

 

[jeremiah89]

The flapper would have been installed in the Y pipe by OMC at the factory, I doubt Renken or any boat company would have changed what the factory set up on their sterndrive packages.

EXHAUST & COOLING - 1991 OMC Stern Drive 5.7 574BPERGD | Crowley Marine

part # 32, just like all the first run OMC Cobras. Volvo removed them from '99 on the SX series, but I don't think that was a good decision.

I removed the risers and piping to the y i don't see any flappers on either side or a spot for them

 

[Lou C]

Are there holes in the Y pipe for the rod that retains the flapper to pass through? If so someone removed them at some point. As long as the holes are there you can buy the parts & reinstall. I certainly would. I’ve had this boat 18 years moored in salt water 6 months out of the year and never had water in the cyls from the exhaust.

 

[jeremiah89]

Are there holes in the Y pipe for the rod that retains the flapper to pass through? If so someone removed them at some point. As long as the holes are there you can buy the parts & reinstall. I certainly would. I’ve had this boat 18 years moored in salt water 6 months out of the year and never had water in the cyls from the exhaust.

If the flappers was missing would it run for hours some trips and 20 minutes other trips? Seems like it would ingest water while I'm backing the boat in the water

 

[Lou C]

not necessarily, if you slow down fast it can surge up the hoses connecting the Y pipe with the elbows. If you never had to slow down fast then it might not happen.
Mercruiser never dropped their flappers. So either you have flappers in the Y pipe, or you remove the exhaust bellows and fit an inboard style flap valve over the exhaust opening in the gimble housing that the bellows was clamped on to. You have to have some way to block the surge of water up the exhaust.

 

[Lou C]

here's what it looks like installed. Not saying it's the only way water gets in but I'd put them back in.

 

[jeremiah89]

here's what it looks like installed. Not saying it's the only way water gets in but I'd put them back in.

I really appreciate all your help man. I pulled everything off in red I'll check it again. If there isn't a spot for it what do you recommend?

 

[Lou C]

I can’t believe that there aren’t the holes in the Y pipe for the steel rod that the flapper pivots on. They would be under the rubber hose that connects the exhaust elbow to the Y pipe. Only thing I could think of is someone removed the flappers and filled in the holes with something like steel putty (JB Weld) or similar. For sure that I/O set up came with them from the factory. For each side you need the flapper, the 2 grommets and steel pin.

 

[jeremiah89]

I really appreciate all your help man.

I can’t believe that there aren’t the holes in the Y pipe for the steel rod that the flapper pivots on. They would be under the rubber hose that connects the exhaust elbow to the Y pipe. Only thing I could think of is someone removed the flappers and filled in the holes with something like steel putty (JB Weld) or similar. For sure that I/O set up came with them from the factory. For each side you need the flapper, the 2 grommets and steel pin.

I'll look again i pulled both bellows off the upper and lower. I wonder if i can purchase a kit to install them or would i need a new Y pipe

 

[jeremiah89]

Do you think i can try this??

 

[Lou C]

nope that's for a Volvo Penta AQ set up. You need the OMC ones, the parts are still available so order up the flappers, pins and grommets.

 

[jeremiah89]

No spot for them at all.

 

[Scott Danforth]

not only is it for an AQ series. its not designed by volvo, not needed on a volvo (they have an external flap) and they are made in china

 

[jeremiah89]

not only is it for an AQ series. its not designed by volvo, not needed on a volvo (they have an external flap) and they are made in china

I don't have holes in my Y pipe for flappers

 

[Scott Danforth]

I don't have holes in my Y pipe for flappers

they may have replaced the y-pipe

however most importantly, what is the water level to riser height (see post #5)