1998 Merc 4.3 Hydrolock

[lanthoma]

Our 1998 Monterey with a 4.3L Mercruiser carb engine (0L038882) hydrolocked yesterday. The engine had dieseled about three engine cycles and when we went to start it again about 20 minutes later I heard the dreaded clunk. I pulled the plugs and water came out #5. The starter would not engage.

Today I cranked the engine by hand and water came out all cylinders. After reading several forums about hydrolock I pulled the exhaust manifolds (bat wing). They look to be in OK condition, but flappers on both sides are gone. New starter will be here Friday. I examined the flywheel through the stater hole and no missing teeth.

This happened before in 2006 and I took it to a mechanic. He told me he replaced the flywheel and starter.

1) Shall I even bother to upload pics of the manifolds or do an acetone test? I suspect the answer will be consider myself lucky that they lasted 20 years and convert regardless of condition.

2) What is the procedure now? The Mecruiser bulletin on hydrolock wasn't very clear about this. I assume replace plugs, change oil, new filter, check timing and idle to eliminate dieseling.

3) Is there anything else I should check? We only use it in freshwater.

Thanks,

Lance

 

[alldodge]

exhaust manifolds (bat wing)

Bat wings need to be tossed, and pics not needed

Dieseling is caused by incorrect timing or running to rich and/or hot. Get the fuel supply fixed after tanking care of motor

Pull all plugs, spray oil in cylinders, change oil. Crank it over a bunch without plugs, and do it now. Once done spray more oil in cylinders and change oil again if needed.

Get it running as soon as possible

 

[Bondo]

I suspect the answer will be consider myself lucky that they lasted 20 years and convert regardless of condition.

Ayuh,..... Welcome Aboard,..... Ya got this part Right,.....
I've lost count of motors I know of, destroyed by those manifolds,.....

The dieseling caused yer current situation though,.....
Ya know that funny soundin' shutter ya hear, Just as it finally dies,..??..??
That's the motor spinnin' over,.... Backwards,......

Lotsa causes for dieselin',....
Track that down, 'n fix it, or the same will happen again, regardless the exhaust system used,.....

 

[lanthoma]

Thanks guys. I didn't think it would even be worth buying acetone to test these manifolds. And I'm sort of into recycling so that negates the old float test, but if the scap metal yard will give me $0.05 then they are out of here.

The good news is that since everything is apart I can get a nice line on the crank for timing. Hope that solves the dieseling.

 

[Scott Danforth]

Idling for one minute after a long run often prevents dieseling

Get rid of the batwings. Problem prone design from day one, they make bad anchors and kind of suck as paper weights or tire chocks

Since the weight is under a ton, not sure they have much scrap value

 

[lanthoma]

Well they sure felt like a ton when I lifted them out of the boat today. Theres a scrap yard in town that pays by the pound so I *might* get enough money to buy half a gallon of gas.

I had an 1971 Ford truck that would diesel no matter what I did to the engine. The only solutoin, as you suggested, was to let it idle a bit before shutting it off.

 

[cableguy1979]

Do a compression test. Water doesn't compress and something can give like a bent rod. My question is are the manifolds bad or did water get in through the exhaust another way? I know its unlikely but before you call it done I would check them although it sounds like they are junk.

 

[JoLin]

One more thing to check. When it happened to my 4.3 (hydrolock), trying to restart it broke the starter boss off the block. It's an "ear" cast on the block that the outer starter bolt screws into. When I started researching it, I found numerous accounts of that piece snappong off GM 4.3's, 5.0's and 5.7's. It means either welding the block (tricky) or replacing it.

My .02

 

[lanthoma]

Cableguy - I don't know for sure how the water got in the cylinders. It could be the manifolds, but I think it most likely occurred when the engine dieseled. Both exhaust flappers were gone, so that's a possibility too. The manifolds might be OK, but it sounds like it wouldn't be worth the gamble. I'll be sure to do a compression check... it's one of those things I'm sort of afraid to do because it could identify additional damage, but if it looks OK I'll be happy I did it.

JoLin - That would be bad. I put the starter in tonight so I guess I was lucky that the ear didn't break off. After the first Clunk the starter was toast so it didn't have much of a chance to break anything else.

 

[JoLin]

JoLin - That would be bad. I put the starter in tonight so I guess I was lucky that the ear didn't break off. After the first Clunk the starter was toast so it didn't have much of a chance to break anything else.

Glad to hear it. It was a real shocker to me when it happened. Expensive, too.

 

[Rick Stephens]

Glad to hear it. It was a real shocker to me when it happened. Expensive, too.

That's for sure. Be the last thing I would expect and the last thing I would be ready to spend to spend biggish dollars on. Wow.

 

[gergAlicious]

My 4.3 used to diesel and when I put it back together I found the timing was almost at TDC. Once corrected, it hasn't dieseled at all.

 

[lanthoma]

Alright, everything is back together with a new starter and conversion from batwings. The engine started right up! However I noticed that the port side exhaust and riser were hot compared to the starboard side, which were cool enough to touch. If I pull the blue drain plugs a lot more water comes out starboard than port. The hose from the top of the engine to the exhaust manifold is clear. Any ideas? Maybe the new exhaust flapper is misaligned and blocking flow?

 

[alldodge]

This is not an issue, the port side will always be a bit hotter, just the natural flow of water. Water flows the path of least resistance. So lang as you can touch it without an instant burn, your good

 

[lanthoma]

Thanks everyone for your help. I took the boat out today and it ran great. Bondo was right about dieseling causing the engine to run in reverse. I saw the serpentine belt going backwards after I shut off the engine to hook up my timing light. Timing turned out to be OK. I think the problem with dieseling was high idle. The carb linkage attachment to the engine was too much Aft so reattachment pulled the carb opne a bit and kicked up the RPMs to about 800. A little adjustment and now it sticks at 600.

One last question - I noticed these replacement exhaust manifolds have several brass plugs in them that were not present inthe bat wings. Do these need to be pulled out when I winterize or do I stick with the the blue spigots and plugs in the block?

Thanks again.

 

[achris]

Just pull the plugs out of the bottom, stick a nail or small screwdriver in to ensure the holes are clear and all the water drained out...

Chris.......

 

[Bondo]

Bondo was right about dieseling causing the engine to run in reverse.

Ayuh,..... Sorry,..... I just enjoy readin' that,......

The core plugs in the manifolds are just like the core plugs in the block,.....
Left over holes from the castin' process,.....
Drain the manifolds just like the block, through the drain holes, 'n make sure to poke the crud outa the way with a screw or nail,.....