New 6.2 Mercruiser Fails after 36 hours

jgyatesjr

jgyatesjr

Member
Oct 27, 2008
51
Live in Waterford, VA and boat in Potomac River
Boat Info
1999 Sundancer 260
Engines
Mercruisre MX 6.2 MPI with Bravo III (repowered from 7.4)
I have a new 6.2 with closed cooling in a 1999 Sea Ray 260 Sundancer and the engine has failed after only 36 hours on it. I have babied it since it was installed last September 2014 only going over 4,000 after 20 hours. I was running 22 pitch props but it would only rev to only did 4,200 RPM at WOT so I switched to Hill 4 blade Signature 18 pitch props. On the first test run, I got it got to 4,800 but then engine lost power. There were no alarms. When I put in neutral it died. When I got it restarted, it was missing terribly so cut it off and got tow to slip. I called Mercruiser and they said have local Mecruiser dealer ck it out. He quickly determined that there was no compression in two cylinders and low is the next one, all on the right side. The plug electrodes were gone in the cylinder with no compression. This seems un-real to me. Engine goes bad in first 36 hours! Anyone have similar issue with 6.2?
 
what you describe is detonation from a very lean mixture. Depending on your cool fuel unit ,it could have been painted inside and is now flaking off into the fuel system clogging the injectors.
It would be beneficial to have them removed and tested.
 
Like mentioned, not sure which fuel system you have but, I would think fuel restriction or improper timing maybe combined with an overheat. Any 1 of those 3 could do it.
 
Standard sea Ray tank. I think plastic. It is brand new Mercruiser MPI engine and fuel system has filter with only 36 hours on it. You suggesting fuel filter clogged?
Doesn't ECM set timing? But it has always been slow to start and I swear it has had a miss since new. ECM do wonderfully in correcting to make engines run but may hide issues.
 
If this is a brand new "crate" motor from Merc, it's not a CF3 issue since they switched to CF4 in 2009 (maybe 2010). CF3 had problems with the paint they put inside the fuel chambers of the Cool Fuel Unit flaking off (ethanol to blame????) and moving down the line to the next stop....the injectors.
 
What warranty did they give you ? disclaimers ? Was this a plug and play unit or was there fine print on the install ? Does the installer have any liability here ?
 
Just a thought if you took it to a Certified Mercruiser mechanic did he pull the fault codes out of the ECM? With what you have described there should be enough info in the ECM to get an idea of what's happening with your setup, it should have at least put you in guardian mode. Are there any error codes on the smart craft? More info on your setup would sure help.

I do have a friend with a 2001 5.7l repowered to a 6.2 horizon mpi with his smart craft he spent months troubleshooting compatibility problems between versions of the ECM & smart craft.
 
Update: Mercruiser rep asked for the PDI (Pre-delivery Inspection) form from the initial install in Sept 2014. I requested a copy from the installer and sent it to Mercruiser rep. The form was incomplete for example it did not list the props size or RPM at WOT. Evidently, the installer also entered the info in MercNet but it too was incomplete. So, now Mercruiser has decided to have the marina pull the engine and ship it them for detailed examination. I will get back when we again hear what Mercruiser says.
 
jgyatesjr said:
Update: Mercruiser rep asked for the PDI (Pre-delivery Inspection) form from the initial install in Sept 2014. I requested a copy from the installer and sent it to Mercruiser rep. The form was incomplete for example it did not list the props size or RPM at WOT. Evidently, the installer also entered the info in MercNet but it too was incomplete. So, now Mercruiser has decided to have the marina pull the engine and ship it them for detailed examination. I will get back when we again hear what Mercruiser says.
Click to expand...

That's encouraging. I've nothing but great experiences with Merc and I trust they will do the right thing.
 
Update: Background: Re-powered Sea Ray Sundancer 260 with a 454 with a 6.2 (383) Mercruiser Stroker with aftermarket freshwater cooling. It only last 35 hours before rear port spark plugs had disappearing electrodes. Mercury dealer first said I was overproped. But unlikely. The 454 had a Bravo 3 with 24 pitch props; the installer replaced with 23 pitch but still didn't achieve 4800 to 5200 rpm at WOT so we put on 18 pitch. Just when I started getting to 4800 rpm the engine died. Anyway, Mercury is replacing the engine but now claims that the aftermarket fresh water cooling system was the culprit. The cooling system is a MPS4320-B by Marine Power Systems in New Jersey. Marine Power said they have installed many of these systems and have never had an issue. So, who to believe. Anyway, Mercury is replacing the engine but will not provide a warranty if I install the aftermarket cooling system. Guess I have no choice in the matter. Hope to be in water in April! What a saga. Oh, when the technician checked ECM on failed engine, there were none indicating a problem.
 
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If your cooling system wasn't doing it's job, the engine would overheat. Alarm would sound, and it would be recorded on the ecm. More likely, it's a fuel delivery problem or lack of it, which the ecm wouldn't record.. Hole in pistons, damaged spark plugs, are a result of sky high cylinder temperatures and could happen without an increase in coolant temp.

Look that over real close or you'll be cooking another one.
 
Tim Jodice said:
Why would you take out a 454 and replace it with a smaller engine?
Click to expand...

I'm very sorry to hear of these troubles with a brand new small block turn key installation.

Just a option for the next person in a similar situation.
The 454/7.4L marine engine in brand new from the factory long block form is alive and well.
This workhorse of a platform has been hauling big boats around for years and doesn't break a sweat pushing nominal horsepower reliably.

Respectfully, I've not heard any rave reviews of anyone going from a big block to a small block.
260 pounds lighter isn't significant in many boats and....the swap likely costs more than a new 7.4L long block..all-in.

Just a thought,
 
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I guess a better question is why wouldn't you replace it with the exact same engine? From what you are saying it sounds like the engine is not up to the task. Needs less pitch in the prop and needs to spin 400 rpm more to get max power. Obviously works but is stressed alot more for a little more power. Why not the other way like a 496? I ask all this because of what little experience I have in boats. When I was shopping for a boat I tested a sundancer 260 and it had a 350 MPI it needed to be at about 3700-4000 to be doing about 25 knots. The mechanic in me didn't like running it constantly at such a high power setting. When I test drove the 280 that I bought I was happy to see the 4.3s spin about 3200 rpm to get the same speed. I forget exactly how much more fuel the 280 burned but I know that it was a little bit more. Not sure if it was because of being a little bit heavier of two less efficient alpha drives hanging in the water. Those with more experience than me I would love to hear from you!
 
Air O'Nautical said:
I'm very sorry to hear of these troubles with a brand new small block turn key installation.

Just a option for the next person in a similar situation.
The 454/7.4L marine engine in brand new from the factory long block form is alive and well.
This workhorse of a platform has been hauling big boats around for years and doesn't break a sweat pushing nominal horsepower reliably.

Respectfully, I've not heard any rave reviews of anyone going from a big block to a small block.
260 pounds lighter isn't significant in many boats and....the swap likely costs more than a new 7.4L long block..all-in.

Just a thought,
Click to expand...

I was just having a discussion with a friend that is re powering and he claims he has not yet found new 454's. I would like to pass your source on.
 
velooce said:
I was just having a discussion with a friend that is re powering and he claims he has not yet found new 454's. I would like to pass your source on.
Click to expand...

If you read performtech info it is not direct 454 replacement , it is wider and 1-1/2" taller just to name few problems. Re-building or re-manufacturing of exsisting blocks or going with small blocks seem to be the only option at this point in time if you have space restrictions.
 
velooce said:
If you read performtech info it is not direct 454 replacement , it is wider and 1-1/2" taller just to name few problems. Re-building or re-manufacturing of exsisting blocks or going with small blocks seem to be the only option at this point in time if you have space restrictions.
Click to expand...

I did this back in 2013...

http://www.1800runsnew.com/newbase-details-NLM.html#454

Great guys to buy from...454/7.4L new long block.
I bought 2, the blocks were cast in 2013 and built new from the GM supplier.

Also, have various new options here...
http://www.michiganmotorz.com/categories-c-0.html

I apologize for the hi-jack from the OP's topic :)
 
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