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VetteLT193
07-02-2017, 12:31 PM
i have twin 6.2 mpi mercs. I had not used it for about a year, there was a sensor issue and life got in the way. I just serviced the boat to get going again... oil, drive oil, raw water pumps, etc. one engine runs fine, the other overheats within a few minutes of the dock. I assumed thermostat and changed it.... same behavior. It doesn't overheat without load.

blockage? Something else? I need some ideas to check. Anyone have a "how to" on backflushing the engine?

Morgan's Cloud
07-02-2017, 03:25 PM
Overheating issues can be a serious :censored: nuisance .
A little bit more background ?
It wasn't doing it before you laid it up ?
Salt or fresh water use ? FWC ?
Running the cast iron exhaust ?
I assume Bravo , not Alpha ?
How old is the package ?

VetteLT193
07-02-2017, 03:38 PM
It wasn't doing it before, I had a sensor issue but otherwise it ran fine.

Boat is a 2008. Factory exhaust. Salt water, flushed with saltaway, bravo. Has silent choice.

I'm leaning towards the manifolds being blocked. I'm just baffled as to why the other engine is running fine when it is in the same environment

Morgan's Cloud
07-02-2017, 04:00 PM
I have a friend who had a 28zxo . I think it was a 2003 or so . It was kept high and dry on a lift . After a few years he developed an overheating problem , first on one engine . It drove the mechanics totally mad. At low , off plane , speeds it was fine though.
They went through everything on both engines about 20 times . Water pumps fine , even the stock manifolds and risers were spotless.

In the end , at which point his bank account was almost empty , some whiz came along and said , 'have you checked the plastic grommets in the transom plate that connect the exterior water hose to the interior hose ? Salt water boat , dry stored , it's about time'

Be damned if that wasn't it !

In time the salt (even fresh water sometimes) gets inbetween the hole in the trans plate and grommet and the corrosion crushes the grommet down creating an air leak in the system . At idle / low speeds the connection is below the water but as soon as you get on plane the problem shows itself.
For some strange reason it also seems to be more common on dry stored Bravo boats than ones left in the water .

Of course, this might not be your problem at all but it's useful to know !

gcarter
07-02-2017, 04:42 PM
A friend had a similar problem. After disassembling the engine, he found the
aluminum intake manifold/iron head water passages were completely corroded
closed. Salt water and dissimilar metals can do these things crazy fast.

Morgan's Cloud
07-02-2017, 05:39 PM
A friend had a similar problem. After disassembling the engine, he found the
aluminum intake manifold/iron head water passages were completely corroded
closed. Salt water and dissimilar metals can do these things crazy fast.


And what's really shocking George, is that nearly all of the new marine engines are made with all sorts of dissimilar metals and no-one tells you.
I never knew that our 502 had dissimilar metals in it but thankfully got FWC from the factory. The dealer I got the Volvo from said at the time of ordering that he orders FWC on all his engines . Much later I find out that it too has amongst other things an aluminum intake manifold .

From here on it's FWC on everything for me !

Ghost
07-02-2017, 07:24 PM
And what's really shocking George, is that nearly all of the new marine engines are made with all sorts of dissimilar metals and no-one tells you.
I never knew that our 502 had dissimilar metals in it but thankfully got FWC from the factory. The dealer I got the Volvo from said at the time of ordering that he orders FWC on all his engines . Much later I find out that it too has amongst other things an aluminum intake manifold .

From here on it's FWC on everything for me !

I love FWC--wouldn't have it any other way.

BUIZILLA
07-02-2017, 07:30 PM
awhile back, Mark in JAX had the same issue on his 22ZX, he fought it for over a year..

might want to date back a couple years, and look up his fix