My boat has a knock, I don't know how it happened.

[baconbiscut]

This is not a mechanical question is first thing I would like to say. Our Formula 25 PC was re-powered back in 2007 with Mercury's MerCruiser 383 Mag MPI engine. After about 200hrs of use I changed props and really screwed up the engine. I heard what sounded like a knocking sound so I took it in I had tulliped two intake valves. So I had the heads refinished and the intake valves replaced with stainless valves.
Anyway, after about 75 hours of easy running the ticking came back, however, after the engine had warmed up ran in the upper RPM range for a while the ticking went away. When I took the boat in for it's 100 hour (now 300hrs) I asked the mechanic to look into it. He ran the engine and he said it deffinately sounded like a knock or a spun bearing. So I had him pull the engine (I've got a bout grand worths of labor into it now) and tear it down. He called me later to tell me he had bad news. I went to the shop and he showed me the engines crank shaft had scoring where every bearing was it was so bad you could drag a nail through the scoring.
So he pulled up some data on the engine and the engine was supposed to have stainless intake and exhaust valves, which it actually didn't have. I have the old valves to prove to this. My mechanic believes that Mercury didn't clean the block out right and it damaged the bearings from the beginning because he said there's no way the crank shaft could have this kind of scoring from just normal running even if the engine was lugged. The mechanic called mercury and they seemed to want to help even though the engine was out of warranty.
If Mercury isn't willing to offer some sort of compensation should I demand it. Or is this one of "Your SOL situations". Also could this be my fault if so what cause the crankshaft scoring there was no debris in the engine. Anyways, any help or advice is greatly appreciated.

BTW, sorry for the long post

-Dan

 

[Summer Fun]

Re: My boat has a knock, I don't know how it happened.

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The mechanic called mercury and they seemed to want to help even though the engine was out of warranty.

Wait until you hear from them it could be good PR for them to help you .

the engine was out of warranty.

It also could be a your SOL situations.

 

[gss036]

Re: My boat has a knock, I don't know how it happened.

Hopefully they have changed thier attitudes at Mercury customer service, years ago I had a Merc 200 hp outboard throw a rod at 140 hours and 13 months on a 12 month warranty and I was SOL. Luckily, I had purchased an extended warranty and only had to pay the state sales tax on a new head.

 

[jpriak]

Re: My boat has a knock, I don't know how it happened.

Just curious, what rpm are you usually running your motor at?

 

[baconbiscut]

Re: My boat has a knock, I don't know how it happened.

Just curious, what rpm are you usually running your motor at?

My engine usually gets 5100 RPM topped out (4800-5200 RPM range). I'm usually running between 3500-3800 RPMs at cruise. The engine has never been overheated either.

 

[arimatation]

Re: My boat has a knock, I don't know how it happened.

You should have had a used oil analysis done. This would show contaminates that would show up if it was a manufacturing problem. I know coulda woulda shoulda......

If it was lugged the bearings could be worn, but not grooved. The fact it should have had the right valves makes you wonder what is going on with the way the engine was assembled. Hopefully they will do good by you.

If not I would get an engine expert to inspect the engine and give you findings that could be used in small claims court....... Assuming that the factory botched the engine build.

Good luck

 

[Philster]

Re: My boat has a knock, I don't know how it happened.

I'm not saying it's lugging that caused it, but I can't help but pause in thought when reading this:

"...Changed prop and screwed up engine..."

To me, that means you went up in pitch or added some form of load to the engine, which could also be from adding blades.

Lugging = tulipped valves. It's hard on bearings, too. It's hard on everything.

Under load, when the engine is pulling up in RPM, all is good unless the engine is overfighting and losing. Too much pitch and you run at wide-open-throttle (WOT) or with a lot of throttle and it's lugging.. and lugging... and lugging. Eventually, the stress against the metals is too much. If the engine is done accelerating the boat, the throttle must be pulled back. If max speed is hit at 4800 rpms with the throttle 90% open, the remaining 10% of throttle is all at the expense of lugging the engine. Trimming the drive plays a role too, because not trimming it up adds more stress.

I'm not diagnosing your engine because there are sooo many variables, but I can't get past the prop = engine screw up.

 

[baconbiscut]

Re: My boat has a knock, I don't know how it happened.

The damage made from the prop was instantaneous. I put the prop on ( I went from a SS 19p 3-blade to an aluminum 17p 4-blade) and hit the gas for a hulshot it got to about 4600 (200 below rpm range) and I heard pinging I slowed the engine down took back to the dock put it on the lift the changed the prop and when i got the chance i drove the boat to the marina. Was that enough time damage the crank?

 

[180Fisherman]

Re: My boat has a knock, I don't know how it happened.

I've heard the Merc 383 in general has/had more than it's fair share of problems. Seems there are/were some lubrication issues with a relatively large number of those engines.

 

[Philster]

Re: My boat has a knock, I don't know how it happened.

Hmmm... from SS 19 to alum 17. I don't know. But if there were a lube issue, it'd rear it's ugly head under a quick spin up like that. The alum flexes (adds slip) and a 17 is going to spin up faster than a 19, so it might have brought a lube issue to the surface real fast, even though you've done nothing wrong, provided you didn't over rev the engine, based on your quoted RPMs, but my skeptical side says we got part of the story, or your didn't track the tach the whole time you did the hole shot and blew red line big time.

I don't know what you consider 'hole shot', but I hope it's nothing more than a progressive push fwd on the throttle, because I would never go from 0-100% throttle in a couple ticks of the clock. Dropping the hammer is big lugging-potential load, and with a new prop it's also a major over-revving risk.

 

[tashasdaddy]

Re: My boat has a knock, I don't know how it happened.

i will say this for Dan, even though he is 16, he is one of the most competent Captains, in this area. when he says he did not abuse the engine, i do believe him. sounds like he got the LEMON.

 

[ezmobee]

Re: My boat has a knock, I don't know how it happened.

Came here to say that ^^^^

 

[180shabah]

Re: My boat has a knock, I don't know how it happened.

I never caught that Dan was only 16, and it is right there in his sig too.

 

[baconbiscut]

Re: My boat has a knock, I don't know how it happened.

Hmmm... from SS 19 to alum 17. I don't know. But if there were a lube issue, it'd rear it's ugly head under a quick spin up like that. The alum flexes (adds slip) and a 17 is going to spin up faster than a 19, so it might have brought a lube issue to the surface real fast, even though you've done nothing wrong, provided you didn't over rev the engine, based on your quoted RPMs, but my skeptical side says we got part of the story, or your didn't track the tach the whole time you did the hole shot and blew red line big time.

I don't know what you consider 'hole shot', but I hope it's nothing more than a progressive push fwd on the throttle, because I would never go from 0-100% throttle in a couple ticks of the clock. Dropping the hammer is big lugging-potential load, and with a new prop it's also a major over-revving risk.

Remember that the 17p aluminum prop was a 4 blade. Also our boat is a beast (6500lbs) It sometimes takes all the engine has to get up when loaded down with four or more people. From what I've learned about marine engines is that if propped right, which ours is you can bring the the throttle up to wot without causing damage. I understand that slamming down the throttle is bad for an engine but how does a marine engine avoid lugging at hull shot. I did not run the engine for a long period of time with the 4blade prop I already said this earlier.

 

[JB]

Re: My boat has a knock, I don't know how it happened.

How is this not an engine discussion, Dan?? Sure reads like an engine discussion.

 

[grego]

Re: My boat has a knock, I don't know how it happened.

IMHO. The change of prop, should have made little difference, even doing hole shot. "But!!" Doing a hole shot, with a boat that has not been driven for a while and not warmed to operating temp and low "OIL" pressure, Could do a lot of damage.

 

[Philster]

Re: My boat has a knock, I don't know how it happened.

That engine, that boat/size and 'hole shot' should not be used in the same sentence.

Come on... switched props, went alum, up in blade count, had trouble right after prop change AND said "hole shot".

It could very well be a lemon, but I still don't like what I am hearing about how/when she tullipped valves and went a knockin'.

 

[seven up]

Re: My boat has a knock, I don't know how it happened.

I don't know what you consider 'hole shot', but I hope it's nothing more than a progressive push fwd on the throttle, because I would never go from 0-100% throttle in a couple ticks of the clock. Dropping the hammer is big lugging-potential load, and with a new prop it's also a major over-revving risk.

Yup, we always drag the water skiers across the bay while we are ramping up the RPMS.




oops, time to move to the water skiing forum

 

[Philster]

Re: My boat has a knock, I don't know how it happened.

0-100% throttle does not provide optimum performance, so if you're being cute with your comment, you too are doing dumb things to your engine.

You might have virtually identical performance with proper/progressive application of throttle without stressing the engine in ways that are not necessary.

Further, one might get away with it on certain boats/loads/conditions, but given a certain motor, a certain boat, a certain load, and a certain prop and I am not going to be surprised to hear some people over stress their engine.

Hey, hole shot a 6500 lb boat all you want. "Getting a skier up" and "hole shot" are different things to different people. Far too often, hole shot means pushing hard/fast on the throttle in a way that does NOT provide any additional/meaningful acceleration, but it does severely stress all the mechanical components.

 

[baconbiscut]

Re: My boat has a knock, I don't know how it happened.

0-100% throttle does not provide optimum performance, so if you're being cute with your comment, you too are doing dumb things to your engine.

You might have virtually identical performance with proper/progressive application of throttle without stressing the engine in ways that are not necessary.

Further, one might get away with it on certain boats/loads/conditions, but given a certain motor, a certain boat, a certain load, and a certain prop and I am not going to be surprised to hear some people over stress their engine.

Hey, hole shot a 6500 lb boat all you want. "Getting a skier up" and "hole shot" are different things to different people. Far too often, hole shot means pushing hard/fast on the throttle in a way that does NOT provide any additional/meaningful acceleration, but it does severely stress all the mechanical components.

I don't firewall the throttle by slamming it down. I ease it up to full sometimes just to get up. I just don't see how any of that would create scoring on every bearing on the crank shaft that's so pin point you can drag a nail through. This is why my mechanic suspected debris caused this. He found a few metal shavings in the oil pan but he can't any place where they may have come from.

I'm not trying to get a free engine from Mercruiser we bought this engine new, we invested over three grand into it for repairs that didn't have to do with regular maintence fees, I've brought it in for regular maintence. The reason I posted this was to see if Mercury went wrong here. They were already dishonest about the valves they put into this engine what else did they not do. I want to know before i have to spend 5 grand on a new crank.