4.3L hydrolock

[riverratjody]

This is my first post to iboats. I've been reading for hours/days the wealth of knowledge found here and finally got my thoughts together to seek help. I've read everything I can pertaining to hydrolock on this site and hope I have my problem diagnosed, but I need you help.
4.3L (Gen+) Mercruiser, 262, 2bl carb. 1998, SN 0L319057.
Boat ran fine all summer until about a month ago when I thought the starter broke. But it hydrolocked. It had dieseled for a very long time and from reading here, I thought it had sucked up water through the exhaust. Since I also thought I broke the starter when I tried to start it, I went ahead and replaced it. I forced the water out, oiled the cylinders, replaced the plugs and learned how to decrease the chances of dieseling. It ran like a charm for about a month until this weekend. It ran great for 2 days and on the 3rd evening on the water, I went to crank it for one last run and it was hydrolocked again. It sounded like it broke my starter bendix again. It had not dieseled, I did not stop suddenly, I idled for a long time from the no wake zone to the shore, and as far as I know it has never run hot. I got it home and pulled the plugs and all 3 cylinders on the starboard side were full of water and the rear cylinder on the port side had a little water in it. I'm guessing that both of my exhaust manifolds are rusted through on the inside and allowing water to enter the cylinder. I have the one piece batwing manifolds so I can't look inside them or use the acetone method to see if they leak. I do see a little rust around the bolts that hold them on. Does this sound right, or do I possibly have worse problems? If I have to change the manifolds to a 2 piece, that will be another post, but I think I'm on the right course there also, thanks to this site. Thanks so much for any help.
Jody

 

[riverratjody]

Re: 4.3L hydrolock

No ideas from anyone? Did I give too much information? I sure need help. Maybe I should have been more direct, like this:

Is having water enter all 3 cylinders on one side, and 1 cylinder on the other side of the engine a clue that the exhaust manifolds have rusted through?

I know Don S is a genius on this particular subject, as I've read all his posts, but no one has stated their question like this. Please someone give me some ideas. Thanks.

 

[Chris1956]

Re: 4.3L hydrolock

Well if you run in saltwater, it is time to change the manifolds. If you run in freshwater, they may have developed cracks over the winter or had some defect.


I suppose you could test them by removing them from the motor, and filling the waterjacket, to see if it leaks into the exhaust passage.

 

[jtybt]

Re: 4.3L hydrolock

Yeah, if this is a saltwater boat, 11 years is WAY overdue if these are original manifolds.

It's good you do the long idle/cool down period after a run. It also sound like you went thru the right procedure after the hydrolock. Lets hope a manifold change fixes your problem.

 

[fishingman220]

Re: 4.3L hydrolock

i had water in my cylinders and it ended up being the gasket between the manifold and riser. but you say you have one piece manifolds so that cant be it, i would say pull manifolds and look indisde, and do the test you said in your post, also pull the exhaust and look at your flappers

 

[riverratjody]

Re: 4.3L hydrolock

Thanks guys. You've got the same idea I had so I'll pull the exhaust and see what they look like. Never been in salt water, but either the exhaust or the flappers could be rusted. Thanks for the help.