Mercruiser 350 mpi hydraulic locking

[alldodge]

Is it possible the chain could slip or break maybe ?

Anything is possible, could also have bent rods or other things

 

[QBhoy]

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..........

Hi Chris. Was hoping you would also turn up. Appreciated.

You’re of course correct about how the timing is controlled but is it not possible for the cap to cross fire if damaged perhaps.

AD has a point about the timing chain ? It’s a hell of a bang when it happens. Not like any water lock I’ve heard and doesn’t sound as if it’s from the starter like usual. Almost as if the engine is firing against its self.
Wjen it initially happened it was bad enough to throw the belt off it.

Although previously thinking along the lines of inlet manifold after ruling out exhaust side...surely it would lock whether it’s getting fuel/ignition or not (with the kill switch on or off ?).

With the exhaust system off completely on that bank there is nothing like the water or was seeing previously at the plug holes. Almost nothing now if at all.

havent had it plugged in at all. The local merc guy is up to his eyes in the usual frost damage and servicing stuff.

 

[achris]

If it had broken the timing chain, with the ignition and fuel OFF, you'd hear a difference in the way it was cranking. You'd hear some cylinders not compressing.

Also, with the chain broken/gone, the ECU would get on cylinder position information, so you'd get no fuel injector pulses or sparks.

A really quick and totally positive check for the chain is to lift the dissy cap and crank the engine. Dissy turns, chain good, dissy no turn, chain not so good.

Chris.....

 

[QBhoy]

If it had broken the timing chain, with the ignition and fuel OFF, you'd hear a difference in the way it was cranking. You'd hear some cylinders not compressing.

Also, with the chain broken/gone, the ECU would get on cylinder position information, so you'd get no fuel injector pulses or sparks.

A really quick and totally positive check for the chain is to lift the dissy cap and crank the engine. Dissy turns, chain good, dissy no turn, chain not so good.

Chris.....

Thanks Chris. Head is scrambled this late at night here.

I think next time at the boat i have a few things to try. Going to pull king lead off and try cranking and see if it’s the same or if it turns over with out locking. This would rule out the fuel. Don’t think it’s that anyway. If it was then the other bank would have been affected. I’ll also rule out water ingress (or further ingress if it was initially caused by exhaust gaskets passing) by draining it down and isolating the water from the pump discharge side. Now thinking it’s immediate issue may well be timing related after the initial lock up force.

What you think ?

 

[achris]

...What you think ?

You're the man on the ground. We can only advise based on what you tell us you're seeing/hearing.

Me? I'd be putting my Diacom-loaded computer on it and see what the ECU is seeing and if there are any codes set... I'd use that to rule out any ECU/sensor problems, then start on with the mechanical side. But until you can rule out the ECU/sensors, it's a complete guessing game.

Chris.......

 

[QBhoy]

You're the man on the ground. We can only advise based on what you tell us you're seeing/hearing.

Me? I'd be putting my Diacom-loaded computer on it and see what the ECU is seeing and if there are any codes set... I'd use that to rule out any ECU/sensor problems, then start on with the mechanical side. But until you can rule out the ECU/sensors, it's a complete guessing game.

Chris.......

You’re spot on Chris. I’ll see if the merc dealer will lend me the rinda. I know him well enough.
I’ll report back and see what I find. Try get a video too.

 

[alldodge]

Sensors show high or low, so if one comes on sooner.later then expected it still comes on/off. Going to be interesting to see what a scan for codes will show for a mechanical issue

 

[Luv2fish36]

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.

Were you on the boat when it happened? Did the motor suddenly shut off out on the water at high speed or accidentally get shut off at high speed when it threw the serp belt? If so that would explain water coming into the cylinders.

 

[QBhoy]

Were you on the boat when it happened? Did the motor suddenly shut off out on the water at high speed or accidentally get shut off at high speed when it threw the serp belt? If so that would explain water coming into the cylinders.

Hi again.

I wasnt on it at the very moment. I was on my own boat and later towed him and family in. Just to get off the water safely.

Since posting this I’ve talked to him more. Exactly this happened.

He was running wot flat out for a few mins...slowed down to idle. Didn’t stop engine (as first thought). Idled for a few minutes. Went to take off and opened throttle and it stopped at little more than idle rpm. It then would start again. Noticed belt was off. Put back on. Same.

A few few days later I pulled all plugs and lots of water from port bank. All cylinders. Oiled bores and replaced plugs. Cranked for less than a second. Same again. Figures all plugs and cylinders being wet, must be from a common source like manifolds and risers. The usual. Despite it being a slightly heavier noise than anything I’m used to when the starter locks. Didn’t sound like the starter locking. Took exhaust and risers off to pressure test. All good.

Currently port exhaust and risers off. Plugs in and dry. Turns over freely as you like with no noise with lanyard kill activated so no fuel pump or ignition. Turn it on and crank. Big Bang and halt. Doesn’t even get to fire up. Slight kick and bang instantly. Pulled plugs. Not much sign of water. Perhaps only slight residual.

What are you thinking about the belt ?

 

[achris]

... Going to be interesting to see what a scan for codes will show for a mechanical issue

The idea is that if no codes show up, then you trot off looking for a mechanical issue. Obviously a mechanical issue wouldn't throw a code... Use code checking to rule out things, and then go looking at what hasn't been ruled out...

Chris........

 

[Grub54891]

HHmmmm… I think it's a timing issue myself. After messing with it a few times, it's pretty easy to mix up the plug wires. Or the chain jumped a tooth or so.

 

[achris]

HHmmmm… I think it's a timing issue myself. After messing with it a few times, it's pretty easy to mix up the plug wires. Or the chain jumped a tooth or so.

Chain jumping a tooth wouldn't change the timing. This is an MPI engine, timing is controlled by the ECU and the crank angle sensors, not the distributor...

 

[QBhoy]

Chain jumping a tooth wouldn't change the timing. This is an MPI engine, timing is controlled by the ECU and the crank angle sensors, not the distributor...

This is ultimately true Chris....but the timing can be altered by the diz moving. I know it’s not the way to adjust it, but it does alter it. The failure of the cap would surely cause issues too ? Wonder if the cap has been damaged by the initial trauma when it first took water (perhaps by a failed gasket) lots to look at next time.

Thnaks to all.

 

[achris]

Moving the distributor will NOT change the timing, only the firing order (moving it one step round)....

Chris.......

 

[QBhoy]

Chris. It’s not the way to do it. Totally agree, but it does slightly change by doing this. I had to do it to get this engine to even run at all initially. Only a few mm though.

 

[Luv2fish36]

Hi again.

I wasnt on it at the very moment. I was on my own boat and later towed him and family in. Just to get off the water safely.

Since posting this I’ve talked to him more. Exactly this happened.

He was running wot flat out for a few mins...slowed down to idle. Didn’t stop engine (as first thought). Idled for a few minutes. Went to take off and opened throttle and it stopped at little more than idle rpm. It then would start again. Noticed belt was off. Put back on. Same.

A few few days later I pulled all plugs and lots of water from port bank. All cylinders. Oiled bores and replaced plugs. Cranked for less than a second. Same again. Figures all plugs and cylinders being wet, must be from a common source like manifolds and risers. The usual. Despite it being a slightly heavier noise than anything I’m used to when the starter locks. Didn’t sound like the starter locking. Took exhaust and risers off to pressure test. All good.

Currently port exhaust and risers off. Plugs in and dry. Turns over freely as you like with no noise with lanyard kill activated so no fuel pump or ignition. Turn it on and crank. Big Bang and halt. Doesn’t even get to fire up. Slight kick and bang instantly. Pulled plugs. Not much sign of water. Perhaps only slight residual.

What are you thinking about the belt ?

What model boat is this? Big tub? Has the original motor been replaced? Is the riser height vs water line correct? Does this exhaust system have spacers? Sounds like he came down off plane and sucked water back in through the exhaust . Perfect storm would happen if the riser height was too low, burned out shutters, extra weight in the back of the boat.

after you turned the motor over to get the water out and oiled the cyls, the second time you turned it over and more water came out was most likely just left over water from the initial gulp. Can be hard to get it all out of there. I usually get out as much as possible, fog the cyls then Run it right away on the hose. Hard to start but it'll eventually start and smoke like mad for a bit.

 

[QBhoy]

Agree I shouldn’t have to...but suspect something isn’t right when it was fitted with a new unit by dealer and sat untested until he bought it. But to get it to run without popping and not even making 1200 rpm. I turned it slightly anti clockwise for it to run and get the boat on plane. Not conventional but essential on this thing.

 

[QBhoy]

What model boat is this? Big tub? Has the original motor been replaced? Is the riser height vs water line correct? Does this exhaust system have spacers? Sounds like he came down off plane and sucked water back in through the exhaust . Perfect storm would happen if the riser height was too low, burned out shutters, extra weight in the back of the boat.

after you turned the motor over to get the water out and oiled the cyls, the second time you turned it over and more water came out was most likely just left over water from the initial gulp. Can be hard to get it all out of there. I usually get out as much as possible, fog the cyls then Run it right away on the hose. Hard to start but it'll eventually start and smoke like mad for a bit.

It’s a maxum 2400 scr cuddy.

 

[Luv2fish36]

It’s a maxum 2400 scr cuddy.

Thats a Tub. That would definitely need spacers in the exhaust to raise the riser height. Probably 3" spacers at a min. Or if your dry joint they have differnt configurations. taller risers, different sized spacers to achieve what you need.

You should look at the current exhaust setup.

 

[alldodge]

Probably 3" spacers at a min.

Not really true, a boat can be large but so long as there is 13 inches between the water line and top of the exhaust. In most cases the distance will only need to be increased if the motor is modified