Muff Testing for any cylinder water intrusion

[wireready]

This is more of a question of whether muff testing will verify if you have a water intrusion problem than necessarily telling you what kind of water intrusion you have.

But after I've inspected risers, manifolds etc etc- and I want to be confident I don't still have water coming in anywhere else- Can I just run the motor on muffs up to temperature then shut down with the water still going on the muffs and then open the plugs, crank the motor and if no water comes out- is that a good indication that I won't have water inflitration when I put it on the water? If the engine runs and starts smooth, compression is good and oil is clear- is muff running a good enough test ?

Or can manifolds behave quite differently when you're actually on the water boating vs just running up to temp at idle and shutting down while still on the muffs?

I'm assuming that it's a lot better and less stressful to the engine to find out you have water in the cylinders by pulling the plugs and cranking - than trying to start a hydrolocked motor.

Lastly can an engine hydrolock when it's up to speed at high RPM or is hydrolock something that only occurs when trying to start an engine back up? The idea of hydrolocking at high RPM gives me shivers... Never happened to me. The torque from the starter motor is one thing - the torque/inertia involved with a motor running at high RPM scares the crap out of me. Just want to know if it's possible. If so maybe I'll do a little more tear down than just running it one more time on the muffs. I've already inspected my riser/manifolds and it looks reall good and I'm beginning to think water just got in their thru my carb because it wasn't covered with plastic and we had some thunderstorms and downpours while it was in "dry" storage. I'm hesitant to pull more stuff apart if a muff test is a good indication if I still have any water issues.

 

[HT32BSX115]

Re: Muff Testing for any cylinder water intrusion

Or can manifolds behave quite differently when you're actually on the water boating vs just running up to temp at idle and shutting down while still on the muffs?

Howdy,


You get a better "test" by running the engine in the water. More power means more heat stress on an engine that might not be detectable at idle. also, the raw water pump puts out FAR more water at "speed' than at idle.


Water that leaks into the exhaust area from a cracked manifold or riser cannot cause a hydrolock while en engine is running because the water gets blown out along with the exhaust. (UNLESS you have a SEVERE reversion problem due to the wrong type of camshaft installed...........but you would get reversion even if the exhaust system has no cracks......)



The hydrolock happens immediately after shutdown (if you try to crank it right away) . The crack/leak allows water to run right back into the exhaust system and into exhaust valves that remain open after the engine stops turning.

Those cyls with open exhaust valves will have water in them when you try to crank the engine later.

When I had that problem, I didn't get a hydrolock if I let the engine sit for a few hours (or over night) The water simply leaked past the rings and into the crankcase.

It would start right up then......The little bit of water would then evaporate out of the oil if I ran it long enough to warm up completely.

 

[NHGuy]

Re: Muff Testing for any cylinder water intrusion

Have you already found any water? if so, where was it? Was it on first startup of the season? Are you in an area that freezes during winter?

 

[wireready]

Re: Muff Testing for any cylinder water intrusion

Yes just the first startup of the season on muffs after I changed spark plugs. #1 and #6. #1 is rear port and #6 is rear starboard... (1995 4.3LX V6)

Yes Kansas boat- cold winters. Bought boat at an auction at marina cheap- previous owner of this 1996 boat hadn't paid his bills. I found the boat in winterized condition- he had several hoses disconnected at the lower junctions. I pulled drain /manifold plugs last fall and verified there was no water. Granted I didn't think to remove the spark plugs because it appeared to have been winterized. I have no idea how long the boat had been out of the water by the previous owner. He was wrestling with a sheered starter motor bolt that he was unable to extract. That was the first thing I worked on and it came out easy. I then checked fluids, drained old gas changed the spark plugs etc- put in a new starter and she was hydrolocked on the first crank. I then cranked the water out- checked compression, and she starts and runs great on muffs. Granted I've only been running a couple minutes at a time- I haven't run her up to temp yet because I was looking for advice whether it was safe to even try that.

Water that came out was rusty so I'm assuming this was not fresh water from my garden hose -and best case was condensation that formed in the engine compartment since February - if it had been in the cylinder since the last time he ran boat then it was in there all winter.

It only hydrolocked the first time when I pulled it out of storage. I Have run it on muffs, starts and runs fine- granted I've only run for a couple minutes at a time. starts first turn of the key- runs incredibly smooth and quiet- and oil is staying clear. I can start, run a minute or two, shut down, and start it immediately back up. I was thinking of running her fully up to temp- (5 or 10 minutes?) and then immediately trying to crank and fully drain the oil and take one more look at the oil. and if it remains clear- I'm assuming my block and heads are fine.

Compression is also good and consistent on all 6 cylinders.

I'm trying to know the pros and cons of just putting her on the lake for some light sea trials to make sure she continues to start and run smooth and the oil remains clear as a good diagnostic - vs risking the time and money pulling manifolds off the motor or taking it to the mechanic. If this was an ocean boat I wouldn't risk it with salt water. But in a reservoir lake- I'm trying to know how risky it would be for me to put it in the lake- try it out- do a shutdown and quick startup and if the oil remains clear to count my blessings.

 

[Bondo]

Re: Muff Testing for any cylinder water intrusion

-and best case was condensation that formed in the engine compartment since February -

Ayuh,... I'm thinkin' maybe Rain water from before you got it....

Put a new Impeller in the raw water pump, 'n Splash it for a Test drive....

You mighta got Lucky....

It more important to Work it under load, than just bringin' Up to temp....