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View Full Version : Mercruiser 5.7/ 6.2 2005 V drive overheating



marcdups
05-27-2009, 07:39 PM
Sorry guys and gulls it is not a Donzi, but am stumped, Motor serial # is OW 394838. ghecked all systems, replaced water pump impeller, whay a B...., had to remve all eahaust system to get too, so replaced both while at it, checked intake and hose, strainer, all clear, did merc test for 10 quarts of water for 15 secs, on the dot, took thermostat out which looked like crap, excuse the language, ran engine and same problem, let engine cool down 24 hrs per mercruiser" customer relations" and did a compression test, following are from 1 to 8 cyls, 180, 17, 165, 180, 170, 140, 155, 165. 3 squirts of oil in # 6 cyl did not improve compression as per their new test, Did a leak down test and at 30 PSI on the differential gauge only got 4 pounds of pressure, with hssing noise through the intake and exhaust. This engine is not fresh water cooled, so kinda of hard to see if a blown head gasket is causing the overheat, which will not happen at idle by the way, only above 1200, also have the new cool riser system, wow for diagnostics !! So I bypassed Mercruiser flushing system all together and made a contraption to see water flow through the block, removed the thermostat housing and only got a very poor flow, from a garden hose at 60 psi, any thoughts, the guy's corrosion warranty expired April 18 TH, amd he is a hour away from me anytime I go and do something different, did u know a new riser gasket is @ 40 bucks ?? any help would be appreciated, Thanks , Towel boy

mrfixxall
05-27-2009, 08:15 PM
Sorry guys and gulls it is not a Donzi, but am stumped, Motor serial # is OW 394838. ghecked all systems, replaced water pump impeller, whay a B...., had to remve all eahaust system to get too, so replaced both while at it, checked intake and hose, strainer, all clear, did merc test for 10 quarts of water for 15 secs, on the dot, took thermostat out which looked like crap, excuse the language, ran engine and same problem, let engine cool down 24 hrs per mercruiser" customer relations" and did a compression test, following are from 1 to 8 cyls, 180, 17, 165, 180, 170, 140, 155, 165. 3 squirts of oil in # 6 cyl did not improve compression as per their new test, Did a leak down test and at 30 PSI on the differential gauge only got 4 pounds of pressure, with hssing noise through the intake and exhaust. This engine is not fresh water cooled, so kinda of hard to see if a blown head gasket is causing the overheat, which will not happen at idle by the way, only above 1200, also have the new cool riser system, wow for diagnostics !! So I bypassed Mercruiser flushing system all together and made a contraption to see water flow through the block, removed the thermostat housing and only got a very poor flow, from a garden hose at 60 psi, any thoughts, the guy's corrosion warranty expired April 18 TH, amd he is a hour away from me anytime I go and do something different, did u know a new riser gasket is @ 40 bucks ?? any help would be appreciated, Thanks , Towel boy

run engine and pull the block drain plugs, sounds like the engine's coolent passages are full of sand..a head gasket will make it ove heat just so you know or even a cracked head!
as for a dead cylinder,well sounds like you should at leaste pull the head and check the head gasket or valves and cylinder.

MOP
05-30-2009, 02:21 PM
Not to ofetn will you have just one cylinder down between to high reader from a head gasket, more often then not it is a valve issue burnt or bent. Also the fact that you hear the hiss means the escaping air is coming out tells you it is escaping into the air tracts not into the block. I would be pulling the top end apart, if it heated up a few times it needs to be dissected anyway!

Cooling thing! Did you back flush the oil cooler, a bit of eel grass or old impeller shards will cause a huge drop in water flow.

marcdups
05-30-2009, 10:51 PM
Mop, the boat in question has twin application, on the overheating engine, replaced water pump impeller, thermostat, flushed transmission cooler, flushed engine block while by passing Mercruiser,s flushing system, that the customer did not even know he had !! flushed both manifolds, had to remove the flushing system and risers, even though riser gaskets are now @40 bucks a piece for the new cool riser system, and that is four of them :shocking:, as it has the three inch block. Hooked laptop to ECM,s, sea water pressure at 1200 RPM,s on the overheating is 2.9 psi and the other 1.6 psi, so there is a restriction somewhere, but am not getting any help from Mercruiser, Sea Ray or Marine Max for suggestions, as am not a parts changer and see what goes on from there!! Just frustrated ans so is the customer, but if you look at manifolds, blocks and risers the cost is astronomical, and what if it is the block after all or Sea ray,s underwater exhaust systen that they will never admit having a problem with !!

MOP
05-31-2009, 07:16 AM
Tracking down a blockage can be a pain, try back flushing the V drives I have found them full of muck,mud and rust flakes.

Phil

BUIZILLA
05-31-2009, 07:27 AM
the 140 reading is a big clue... that's -22% differential... not acceptable

marcdups
05-31-2009, 08:37 AM
Buzilla, I agree and spoke to mercruiser aboth the low compression issue, but they referred me to http://www.boatfix.com/merc/Bullet/97/97_25.pdf, so go figure ? Bet their tech reps are going to be in the Philippines or India soon!! as they are no help what so ever here. Was told compression was within specs and that was not the problem, I personally believe the water passages in the engine block are clogged, but without removing the long block and getting it boiled out and remanufactured, I do not see how, v drive cooler is clean as a whistle, water pump is new and meets specs, 10 quarts for 15 secs, am about to :hangum: myself, lol

BigGrizzly
05-31-2009, 08:58 AM
And when did mers know all the answers.

BUIZILLA
05-31-2009, 09:00 AM
did you remove the circ pump and inspect the impeller?

marcdups
05-31-2009, 09:07 AM
Big Grizz, how are ya, and good answer, buzilla circ pump running fine, port engine runs like a champ, and does not over heat, even removed boat out of water to check intake grate, nuthing, so I am gonna wait for mercruiser to send their tech rep down, efore I start costing this man a lot of money, he bought the boat new just three years ago and has 284 hrs on it !

BUIZILLA
05-31-2009, 09:30 AM
is the hose from the intake grate to sea water pump collapsing internally? happened to me on the Cary, outside looked good, perfect actually, but the inner layer delaminated and partially collapsed at anything over 1000 rpm.