4.3L Mercuiser Water in Cylinders

[mceagle]

1997 4.3L Mercruiser (carbureted) installed in a 19? Bryant. Freshwater only.

Replaced engine this spring due to damage to the starter mounting flange on block caused by hydrolock. Certified local Merc dealer installed a new engine which now has 20 hours on it and, up to this point, has run great. Last ran the boat July 4, loaded on the trailer and brought it home. That night torrential rains hit the area and the boat was uncovered. The following Wednesday I launched the boat, turned the key and the engine turned less than ? revolution and stopped. Fast forward to last night. Removed all plugs. #2 cylinder was filled with water. Checked oil ? oil was not milky but the dipstick indicated a very high level. Opened oil drain valve and of course, the first fluid to drain, and lots of it, was water. Cranked the engine and water from ALL cylinders spewed out. Removed both manifolds and tested (with risers attached) by simply attacing a hose to the water inlet No water breeched the exhaust ports and, there was no sign of rust or water in the manifolds. Someone suggested that water is draining into the carb (see rain above). Inspecting the plastic carb cover I noticed a crack, approx 4? where it appears that someone over tightened the cover. Opening the carb fully reveals some rust in the intake. Help and advise is greatly appreciated

 

[Bondo]

Re: 4.3L Mercuiser Water in Cylinders

Someone suggested that water is draining into the carb (see rain above). Inspecting the plastic carb cover I noticed a crack, approx 4? where it appears that someone over tightened the cover. Opening the carb fully reveals some rust in the intake.

Ayuh,.... I'd say Mystery Solved,..... Welcome Aboard.....

 

[mceagle]

Re: 4.3L Mercuiser Water in Cylinders

Thanks for the replies. I never would has guessed this. Having had the experience of diagnosing and repairing a Mercruiser with a bad manifold, I was certain that this was the same problem with my friend's Bryant. Time to look for a new cover and Mercury's fastening and sealing system. Darn, learn something new everyday. Again, THANKS!

 

[45Auto]

Re: 4.3L Mercuiser Water in Cylinders

Usually the plastic carb cover just covers the spark arrester. Shouldn't make any difference whether it's cracked (or even on there or not). Hard to see how a crack could let that much water into the engine with the spark arrester below it.

Was the boat stored on the trailer with the bow higher than the stern? If so, I'm having a hard time visualizing how the water ran uphill to the #2 cylinder, unless the whole intake manifold filled up with water. Then it had to drain down past the rings into the oil pan, all in 3 days?

I would be taking a close look at your exhaust manifolds and risers before I blamed it on the rain, or you may be buying another engine .....

 

[mceagle]

Re: 4.3L Mercuiser Water in Cylinders

45 Auto - Thanks for your post -
The boat is stored on the trailer basically level. That much water through the carb into cylinders and into the oil pan doesn't pass a sanity check to me either. Covering the flame arrestor and the plastic cover is the upohstered sun deck as well. On the uderside of the deck, directly above the carb is a vent which the previous owner filled with silicone. I tested the risers and manifolds, as an assembly which did not indicate anything has failed. Any other ideas or clues would be much appreciated - Vortec v-6 marine engines are quite pricecy. Thanks

 

[Bondo]

Re: 4.3L Mercuiser Water in Cylinders

On the uderside of the deck, directly above the carb is a vent which the previous owner filled with silicone.

Ayuh,... Sanity Check or Not,... Sounds like it's been an On-going problem...