Mercruiser 5.7 with Bravo 2 jammed

[jerryb1]

I asked this question on the end of a long post and didn't get a complete response, so I'll try again here.
The boat ran fine for an hour to a destination, temp, etc okay. Then when I went to start it, the engine turns slightly then jams to a stop and will not budge. The motor oil looks clean with no water. I thought it might have water in the cylinders, but when I had that on a previous boat, the water ended up in the oil.
I can shift the drive into foward and reverse with some difficulty but, someone said it would be difficult with the engine not running on Bravo2, so that seems normal. When I do shift it the prop turns as it should in N,D,& R.

I have 2 questions, before I pull the drive off;
1- If it was hydrolocked, would I see water in the oil, or do I have to remove all the plugs?
2- What else can cause this?

Thanks

 

[rodbolt]

Re: Mercruiser 5.7 with Bravo 2 jammed

pull the plugs and check for hydro lock before you shear off the starter bolts.
after that its either an electrical failure or the engine or drive locked up.

 

[TilliamWe]

Re: Mercruiser 5.7 with Bravo 2 jammed

pull the plugs and check for hydro lock before you shear off the starter bolts.
after that its either an electrical failure or the engine or drive locked up.

Exactly.

Do NOT shift a Bravo without the engine running.

 

[jerryb1]

Re: Mercruiser 5.7 with Bravo 2 jammed

pull the plugs and check for hydro lock before you shear off the starter bolts.
after that its either an electrical failure or the engine or drive locked up.

I'm trying to save hours of work by not taking all the plugs out. Wouldn't the water slip by the rings after a day or so and be in the oil?? That was my question.

 

[Bt Doctur]

Re: Mercruiser 5.7 with Bravo 2 jammed

Eventually but the pistons and rings will bond to the cylinder walls first.spark plugs, 10 minutes at the most

 

[dubs283]

Re: Mercruiser 5.7 with Bravo 2 jammed

I'm trying to save hours of work by not taking all the plugs out. Wouldn't the water slip by the rings after a day or so and be in the oil?? That was my question.

hours of work??

no

half an hour??

yes

pull all plugs and mark the plug boots accordingly, ground the coil wire and have a helper spin the engine over and look for water coming from the plug holes in the heads

if water spits out, yep hydrolocked and time for some t-shooting:

start with the exhuast flappers, then move on...

 

[wire2]

Re: Mercruiser 5.7 with Bravo 2 jammed

Water won't drain very fast past properly fitting rings. There's only a few thou gap on each, and the lower ones have oil on them, repelling water. And by the time you wait for that to happen, lots of rust has started.

"Hours of work"? It takes me 15 seconds to pull the boot off, slip a 3/8 drive ratchet/spark plug socket over it, ratchet it until it gets easy, then spin it out with fingers on the insulator.
8 x 15 seconds = 2 minutes.

 

[jerryb1]

Re: Mercruiser 5.7 with Bravo 2 jammed

Thanks to everyone here.
I've changed plugs many times on cars, so I know what's involved. It's easy as long as they are accessable. My old boat had the log style manifolds and a couple of the plugs were hard to get at,like the ones behind the power steering cooler.

I guess it's worth a try to see if it's hydro locked. What I don't know is typical failures of Bravo 2 drives? When they go, do they typically lock up the engine? Maybe the universal joint broke or something like that. I was running with the drive tilted up because I was in shallow water, but I know I didn't ground out. Also, it drove fine and I shut the engine in nuetral, then it locked up when I tried to start it.

My bet is it's hydro locked!

 

[jerryb1]

Re: Mercruiser 5.7 with Bravo 2 jammed

I took out the plugs( and yes it only took a few minutes to do.) Water poured out of the two middle cylinders on the starboard side((3&5 I beleive). At first I thought it was the manifolds or risers, but when I took them off they seemed fine*. With the manifold off, I get water spitting out of what looks like all 4 cylinders on that side when I crank the engine. So I probably have a bad gasket, cracked head, intake manifold? What could it be?

*When I run a hose through the manifold(off the boat), I do get water into the exhaust ports? It seems like I can't get the gasket between the riser and manifold tight enough. Is there supposed to be a sealant on those gaskets? There was none.

My theory is they leaked while driving, but then when i stopped the boat the water got into the exhaust cylinders. I then kept trying to turn it over and maybe I cracked the head or blew out the gasket trying to compress the water??
I'd like to hear your expert opinions on what the heck is happening?
Thanks,

 

[erikgreen]

Re: Mercruiser 5.7 with Bravo 2 jammed

Time for a compression and leakdown test, and/or pull the block apart to look for cracks.

The leakdown test will tell you where the leak is happening, it's more useful than the compression test.

Erik

 

[jerryb1]

Re: Mercruiser 5.7 with Bravo 2 jammed

How do i do a leakdown test and how do I diagnose from that? Do I put compressed air into the cylinder with both valves closed?