Mercruiser 350 mpi hydraulic locking

[QBhoy]

Hi all. Needing some advice. This one has me stumped.

A friends engine recently locked up when out. Was at high speed, slowed down and stopped it. Went to start it and it locked up.

So having spent some time at it myself, we have ruled out the manifolds and risers. They have been pressure tested as good.

All 4 plugs on the port bank have water.

Now here is the weird bit....with manifolds and risers off...it will still lock up with a terrible noise, when trying to crank. BUT....if I trip the lanyard cut out switch to kill ignition and fuel pump...it cranks over just fine and doesn’t lock. This would make me think the water is coming from the fuel injectors ??...but I’m pretty sure it doesn’t have cool fuel or an interface for the fuel and water to mix....and the other starboard bank is clear of water...so surely not from the fuel ??

just to recap...it cranks over fine with no ignition or fuel...but with ignition and fuel it locks up. What’s going on ? It’s run since winter, so not likely to do with frost damage we think.

Thanks all.

 

[Scott Danforth]

look at the flappers.
have the injectors tested, you may have a leaking injector.

 

[QBhoy]

look at the flappers.
have the injectors tested, you may have a leaking injector.

Hi Scott.

I had tjoight of the flappers but ruled that out after clearing the water from bores when stationary and it happened again afterwards.

Injectors leaking are a thought but where is the water coming from ? It’s water that’s locking it, pretty certain not fuel

thanks

 

[Scott Danforth]

verify its not fuel.

only place for water to get into the cylinders is cracked block, leaking exhaust manifolds or reversion / bad flappers

if it was a fuel cooler breach, you would have water in the cylinders along with fuel and it wont run on water.

 

[Luv2fish36]

Not saying this is your problem

I've seen a bad crap cap (distributor cap) cause one to turn over really hard , sounding very similar to one hydrolocking.

 

[TyeeMan]

I was going to say, any chance the distributor could have moved enough to make the timing go way off?

 

[scoflaw]

Timing could be way out, and it's trying to fire with an adverse crank angle.

 

[alldodge]

just to recap...it cranks over fine with no ignition or fuel...but with ignition and fuel it locks up. What’s going on ? It’s run since winter, so not likely to do with frost damage we think.

Not saying this is your problem

I've seen a bad crap cap (distributor cap) cause one to turn over really hard , sounding very similar to one hydrolocking.

My votes with Luv2fish, out of time, either cap or something was damaged during first hydrolock

 

[QBhoy]

Not saying this is your problem

I've seen a bad crap cap (distributor cap) cause one to turn over really hard , sounding very similar to one hydrolocking.

Thanks luv2fish it’s defo not that. There’s water in all 4 of the cylinders.

Thanks though

 

[QBhoy]

My votes with Luv2fish, out of time, either cap or something was damaged during first hydrolock

Ad. The distributor does have an issue for sure. You might remember from previous posts. It’s the same boat. But you reckon it’s causing that horrible noise ?

 

[Bondo]

It’s water that’s locking it,

Ayuh,...... I went down this road a few years back with 1 of the boats I maintain,.....

I wasn't told it had been overheated,.....
I couldn't figure it out for awhile, but eventually did,.....

The heads were cracked in the intake, 'n exhaust ports,......

 

[alldodge]

Ad. The distributor does have an issue for sure. You might remember from previous posts. It’s the same boat. But you reckon it’s causing that horrible noise ?

Just trying to understand the post and for this old guy not clear enough.

Crank with ignition and fuel and it cranks over but stops.
Crank over without ignition and fuel and it keeps spinning

Don't know if its the same kind of stop of not, just reading

 

[QBhoy]

It may well be. If that diz has been damaged it could cause the firing to work against each other and stop it dead with a bang. Good thinking guys. Would explain why it only happens with ignition and fuel on.
Could the water have came from a bad gasket perhaps on the exhaust manifold to riser ? It certainly had nothing like as much water coming out it with plugs removed there, with manifolds off it. Only a slight wisp...instead of the previous pumping of water out the holes.

It threw the serpentine belt off when it initially happened

 

[QBhoy]

Just trying to understand the post and for this old guy not clear enough.

Crank with ignition and fuel and it cranks over but stops.
Crank over without ignition and fuel and it keeps spinning

Don't know if its the same kind of stop of not, just reading

With the lanyard kill switch in normal position it has fuel and ignition. Turn it over and it stops dead with a bang. With the lanyard kill switch off it has no fuel or ignition but allows cranking. Like this it will crank over as long as you like. Doesn’t sound out of the ordinary either.

 

[QBhoy]

Ayuh,...... I went down this road a few years back with 1 of the boats I maintain,.....

I wasn't told it had been overheated,.....
I couldn't figure it out for awhile, but eventually did,.....

The heads were cracked in the intake, 'n exhaust ports,......

Hi bondo. Thanks for replying. This is also a possibility. It previously overheated slightly when the belt came off it last year. But not anything past 190o apparently. I wasn’t there. It has ran fine since, but only for a few hours or so.

 

[alldodge]

kill on - Turn it over and it stops dead with a bang.
kill off - will crank

Might have a bad injector pouring fuel in, but if this is the case, then there should be fuel pushing out the plug holes with the mans off

Do agree, with exhaust mans ON and water present, it could be the exhaust mans. If no water without mans and it still does it, then injector(s)

 

[achris]

MPI Engine... Doesn't use distributor position for spark timing. Uses the crank angle sensor.

QBhoy Have you put a Diacom-loaded laptop on it yet?

Chris..........

 

[QBhoy]

Might have a bad injector pouring fuel in, but if this is the case, then there should be fuel pushing out the plug holes with the mans off

Do agree, with exhaust mans ON and water present, it could be the exhaust mans. If no water without mans and it still does it, then injector(s)

Perhaps AD, but it was defo water in there and you’d think the fuel pump would keep cutting in to maintain pressure if injector leaking bad enough to lock it ?

the timing being so far out may be making sense now guys. The engine has always popped and never ran right since he has had it, it has a blue capped diz unit that was replaced entirely and untested until he bought it. A replacement cap, for what should fit that motor doesn’t fit on the unit fitted currently. All the caps I’ve seen on these engines are black. Never seen a blue one. To get it to run even close to well, I had to turn the unit as far as it would go anti clockwise. We even suspect it was a tooth out. This was put on hold when the water ingress issue came about at the weekend.

 

[alldodge]

To get it to run even close to well, I had to turn the unit as far as it would go anti clockwise. We even suspect it was a tooth out.

Think more now that something broke inside, Gaskets are not real cheap, but cheap enough to find the problem. Suggest pulling heads and timing chain cover

If its black or blue but still looks like a crab cap it should be the same

 

[QBhoy]

Think more now that something broke inside, Gaskets are not real cheap, but cheap enough to find the problem. Suggest pulling heads and timing chain cover

If its black or blue but still looks like a crab cap it should be the same

Is it possible the chain could slip or break maybe ?