2000 V6 Mercruiser overheated, water in cylinders

[Jkrt125]

Hi all,
I've been reading here, learned a lot from the experience here in the forum.

We've acquired a used pontoon boat, 2000 model with Mercruiser V6 Efi model. It's been sitting a few years, not running. I pulled the plugs and on the starboard bank, got quite a bit of water out of the middle cylinder, but all of the cylinders on that bank had some water in them. I spun the engine over on the starter and pushed all the water out, then sprayed WD40 into the cylinders and let it sit for an hour or so. Installed new plugs, and just for the heck of it, tried to start the engine, and to my surprise it fired the first time! Ran a little roughly, but all cylinders firing, so I let it run on the hose for 40 minutes or so. It held 175 on the temp gauge and smoothed out as it ran.

I shut it down and decided to remove the manifolds to check the flapper valves, and both sides were completely gone, only the shafts left. Oil in crankcase looks great.

I'm going to put new flapper assemblies in, and new boots, most likely will replace the "batwing" manifolds with 2pc replacements.

Question; Anybody run an engine that has had water sitting in the cylinder for a while (2-3 years??)? How long before I break a ring? Should I pull the engine now, and bore/hone, new pistons, etc...?
Boat will probably only run 20 hours per season.

thanks in advance

 

[nofuss]

Re: 2000 V6 Mercruiser overheated, water in cylinders

Just my 2 cents. I am a pretty experienced mechanic but new to these GM type V engines, they are rare where i come from in trinidad.
I would say that your engines went through similar treatment as mine,, 2000 4.3 EFIs left to sit for a few years, Mine have 300 hrs on them, I am not sure of the initial "recommissioning" of mine as the person i bought it from got it started up and running. I however soon after buying realized that i was getting water in my cylinders. After removing my manifolds I generously lubricated my cylinders with automatic transmission fluid, through the plug holes, this is a good lubricant, and is also a pretty good rust remover, then I turned over the engine a few times to ensure i spread the lubrication. Yeah the fluid coming out made a mess but that could be easily cleaned up using degreaser.

In your case I would ensure and change the flaps, and change out the manifolds. I pressure tested mine to ensure that, that is where the water was coming from. all failed.
about the rebuild, I would say you have started and run the engine, so good chances its ok. lubricate the cylinders and run it with the starter a few times. Do a pressure test, if all the cylinders are close to each other, get it back together asap. then start it, allow it to warm up at idle. (or and i forgot change the oil) then gradually increase the rpm a little at a time, until u have it running high rpm in neutral, watching your temperature, better done in the water, as u may over heat because of supply on a hose.
then run the boat gradually increasing the speed as in neutral, until u have it really running. this gradual increasing of the RPM would reduce the chance of ring sticking if u do have any rust, and it should wear off any edges that may cause problems. then try to get more than 20hours out of the season

No Fuss

 

[zbnutcase]

Re: 2000 V6 Mercruiser overheated, water in cylinders

I would perform a leakdown test on it before you do anything.

 

[Jkrt125]

Re: 2000 V6 Mercruiser overheated, water in cylinders

Thanks for the replies; I will compression test and try to leak down test in the next day or so.

Hope to have new manifolds this week, will post more results.

 

[dannyual767]

Re: 2000 V6 Mercruiser overheated, water in cylinders

You've run it for 40 mins on the hose and I'm going to assume that it was running pretty decently once all the rust was knocked off the cylinder walls.

You're planning on replacing some exhaust parts and doing a compression and leakdown check. If the checks come out decently, I'd just run the boat and have fun. Sure, your ring seal probably isn't perfect but I bet you got a good deal on your boat purchase and you weren't expecting a showroom new boat/engine. It could give you many years of fun but keep a close eye on the oil level.

 

[Jkrt125]

Re: 2000 V6 Mercruiser overheated, water in cylinders

So,
I checked the compression tonight, and got between 140psi and 170 on a stone cold engine. I think with these kinds of compression numbers, I don't have any huge problems in the engine (yet).
I'll get it back together and run it up slowly and see how it goes...

 

[Jkrt125]

Re: 2000 V6 Mercruiser overheated, water in cylinders

I thought that I would post a follow up to my original post on the water in the cylinders of my Merc V6 I/o.
We replaced the original "bat wing" one piece manifolds with GLM alum. two piece replacements. Ran it for what was left of last season and put about 30 hours on it, and the engine ran great no problems. We left it in the water, did not winterize as we utilized an "engine room" automatic heater in the engine bay. I checked on it several time during the winter and the engine bay was staying over 40 F.
I moved the boat earlier this year to do some out of water projects, and the boat started fine and ran to the boat ramp no problems. We were ready to put the boat in last weekend, and it wouldn't turn over on the starter, roh-oh. I pulled the plug on the middle cylinder bank (#4 same as before) and out comes water! Pulled all the plugs on that bank and pushed the water out, and the boat started and ran fine. Ran it for maybe half and hour, stopped, and it restarted no problem and ran back home no issues.

So, all you veterans out there, would a minor crack in the cylinder wall display these types of symptoms? I guess it could be a manifold, but being the same cylinder as I first experienced the problem, I'm thinking the block/head maybe cracked.

 

[Bondo]

Re: 2000 V6 Mercruiser overheated, water in cylinders

Ayuh,... It Could be a cracked head, But,...
I've personally had sealing Issues with GLM manifolds...
Pull the risers of, 'n inspect 'em for water intrusion...
On Mine, I had to machine the tops of the manifolds so's the gaskets would seal...
The inner exhaust gasket face was lower than the outside edge gasket face...

 

[Jkrt125]

Re: 2000 V6 Mercruiser overheated, water in cylinders

Thanks, I'll check out the risers, but what are the odds of the riser on that bank being bad??
How much material did you have to remove from the riser to square it up?

thanks,