New 6.2 Mercruiser Fails after 36 hours

[vandal]

You went and put a closed cooling system on an engine that was set up with a computer for a raw water cooled engine did you change computer to the one for closed cooling they are not the same at all from timing to a lot of other stuff. If youII

 

[aerobat77]

I think the engine was never right out of factory. A 6.2 mpi is direct replacement for the 454 and should spin about the same pitch prop. If you had to go from a 24 to an 18 pitch prop then it lacked massivly in power before finally failing. A lean burn might indeed be the answer.

 

[jgyatesjr]

"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 ?"


I am dealing with Mercury directly. I had a one year warranty. I dealer which is in NJ has not said that Mercury had called them about the install and initial sea trial.

 

[jgyatesjr]

"You went and put a closed cooling system on an engine that was set up with a computer for a raw water cooled engine did you change computer to the one for closed cooling they are not the same at all from timing to a lot of other stuff. If youII"

Good question. I didn't know that ECM changes would be needed but I would have assumed that the installer would make any needed adjustments. I will check with him.

 

[jgyatesjr]

Why would you take out a 454 and replace it with a smaller engine?

Well, the 454 was 15 years old and showing its age - lots of corrosion; needed heads, etc. The marina had to pull the engine because the transom assembly had to be replaced. When they examined the 15 year old engine, they said it needed heads and manifolds. Didn't seem to make sense to pay marina to purchase a long block (which at the time would be a reman unit and not new) and then transfer over all the 15 year old accessories.... the smart thing seemed to be replace with an entirely new engine...

 

[jgyatesjr]

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!

We checked on a 496 but unfortunately it would not fit in 260 engine bay.

 

[jgyatesjr]

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.

Well marina said Mercury has not identified fuel as an issue for this engine.

 

[jgyatesjr]

I think the engine was never right out of factory. A 6.2 mpi is direct replacement for the 454 and should spin about the same pitch prop. If you had to go from a 24 to an 18 pitch prop then it lacked massivly in power before finally failing. A lean burn might indeed be the answer.

Well I was told that to get the right RPM at WOT, I would most likely have to lower prop pitch or change gearing in the Bravo III outdrive. My boat had a 454 and Bravo III had a 2.0:1 gear ratio. I did not change gear ratio but decided to change prop. We will see how it runs with new engine runs and if RPM at WOT is between the required 4800 and 5200.

 

[jgyatesjr]

Just got boat back in water with new 6.2. Ran at 5,150 RPM at WOT with 18 pitch Hill Marine 4 blade cupped wheels. WOT is supposed to be between 4,800 and 5,200. Impressive hole shots. For now, I am very pleased. (I did not re-gear outdrive). Mercury is warrantying this new engine but only if don't re-install the Monitor 5320 cooling system that I paid $1,200 for. I didn't install it and it is for sale. Mercury claims the aftermarket cooling system caused the valves to tulip and plug electrodes to burn up. Monitor says this is unheard of and the original engine installer said they have installed many many Monitor systems and never had this issue.

 

[Tonka Boater]

Just got boat back in water with new 6.2. Ran at 5,150 RPM at WOT with 18 pitch Hill Marine 4 blade cupped wheels. WOT is supposed to be between 4,800 and 5,200. Impressive hole shots. For now, I am very pleased. (I did not re-gear outdrive). Mercury is warrantying this new engine but only if don't re-install the Monitor 5320 cooling system that I paid $1,200 for. I didn't install it and it is for sale. Mercury claims the aftermarket cooling system caused the valves to tulip and plug electrodes to burn up. Monitor says this is unheard of and the original engine installer said they have installed many many Monitor systems and never had this issue.

Glad you got a new motor but I'm pretty sure you're not supposed to run WOT during the break-in period. I think 3/4 throttle max and only for short bursts until 20 hours. I'm going from memory though.