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Thread: 2.4 ltr running hot?

  1. #1
    gregg canavan
    I just got back from the lake...2nd time out this year, boat ran great...62mph at 5000 rpm. Here's the question...I run a 28' offshore V-hull with tripple mercs. My temp gauges are perhaps screwed up. 2 of my motors are running cool, but the 3rd is running hotter than the others. It has 14lbs water pressure at 5000, but the tell tale stream isnt as strong as the other 2. also the temp of the water coming out of it is hotter. I checked the temp of the hot water coming out of my faucet in the sink with a laser temp gun and that was 140 , it was so hot you couldnt keep your hand in it, but the boat temp wasnt THAT hot, so I'd guess it was less than that. I dont run thermostats, so rule that out and the water pressure is up to 14 lbs...what do you think?

  2. #2
    Boat Racer
    My bet is the impeller, those things need a couple runs, on them, to soften up.....
    One thing, have you made any changes over winter, to kill time LOL? I don't know which engine it is, middle, or outside, but if you made NO changes, I bet on the impeller!
    You need to run washers, where the thermostats would go, that water has to be slowed down to cool the heads!
    Hope this helps..

  3. #3
    gregg canavan
    well I should have told you, the lower unit is a fresh rebuild with a new lower housing,impeller, and upper housing. the motor has all the thermostats cut out so they are only the shell and gasket, eliminating the spring and pellet. What I want to know is how hot is too hot, and how long does it take at 4500/5000 rpm to cook a motor?

  4. #4
    gregg canavan
    more thoughts...I ran this motor HARD today, I just dont know if the guages are accurate. Remember, I do have 14 psi of water pressure and a decent stream of water at the tell tale tube. by the way, its the starboard motor, a 20" right hand nose cone low water pick up unit

  5. #5
    Boat Racer
    MY VOTE IS STILL THE IMPELLER... A new one takes a while... I have started running mine two years, before I replace it(unless a drastic change in temp. occurs)YOU STILL NEED SOMETHING IN THOSE HEADS TO SLOW THE WATER DOWN...
    I can find out what size washers are in mine and post it for you if you'd like!!!
    As for how hot is too hot, I'd say head temp. of 180 deg. would cause me to back off the throttle...
    What about fuel, you aren't leaning it out, is it a carb. or EFI?

  6. #6
    gregg canavan
    ok...I DO have restricters in the heads where the t stats go...instead of using washers I removed the moving parts of the t stats(you know, the spring and the copper pellet as well as the 2 little arms that hold them all together) so the t stat is now a washer with a gasket, no parts to open or close.All 3 motors have new water pumps and this is the only one that runs hot. The other two are mercury impellers, but this one is an aftermarket impeller...still its brand new...I just ran a compression test, 120 psi in all 6 cylinders, even. These are carb motors, no oil injection, I premix all my fuel 40/50:1 merc oil non synthetic all motors run the same fuel, through 2 holley electric fuel pumps at 5 psi to mechanical pumps on the motors. I never run lean, all motors jetted right #2&5 cylinders 82 mains 1346 80 mains. how wet or dry should a piston top look throgh the spark plug hole with a little light...?I need to know whats up here before I have a problem...youre help and thoughts are appreciated.

  7. #7
    Boat Racer
    Plum each head seperately, the right head will run hotter than the left( water travels up higher).. I really don't believe you have a problem..... I think the impeller needs some time on it, mine was the SAME way, until i got some hours on it...
    If you feel you do, you can buy a complete water impeller kit( will have gaskets, the plastic tube( which could be cracked),& a couple other things in it and replace it all....
    Piston tops on mine, look dry.
    [ May 11, 2003, 03:00 PM: Message edited by: Boat Racer ]

  8. #8
    gregg canavan
    hi...thanks for the input...I have found and fixed the problem today...check this out. I sent this lower unit to a marine mechanic over the winter to rebuild. I have used this guy before on other small jobs, he says he is certified and was the top mechanic at the local marine service dealer until he went out on his own. Now mind you I own an auto repair facility, have 2 full time employees and turn a wrench every day...I just dont want to be 15 miles out to Block Island when a lower unit blows up because I did something wrong...so I dont mind paying someone who claims to be a pro a couple hundred bucks in labor to do a job right so I dont have to worry. Well this guy put the WRONG water pump base in...The one he used was for an inline 6, not a V 6, and has a 5/16 HOLE in the side of the water pump base! It wasnt until I blew into the nose cone and heard the air rushing out that I knew where the loss of pressure was. Once I put in the correct water pump base and replaced the unit back on the motor was I assured the problem was fixed. Now I have all the water pressure AND volume to keep that motor cool. And the tell tale stream is twice as strong as yesterday and nice and cool to the touch. Thanks for all your input

  9. #9
    Boat Racer
    QUOTE BY BOAT RACER!!!
    One thing, have you made any changes over winter, to kill time LOL?
    AHHHH, now we're talkin'!!!!!! GOOD TO HEAR.
    [ May 11, 2003, 07:27 PM: Message edited by: Boat Racer ]

  10. #10
    gregg canavan
    if this motor ran warm, almost to the H on the gauge, but not overheated, do you think any harm was done to it? I mean can these motors run a little hot for a couple of minutes or do they get damaged easily? Remember, I still had 14 lbs water pressure, the tell tale water was hot to the touch but not scalding hot, and my compression is even at 120 psi all 6 cylinders. I ran the motor yesterday after replacing the water pump base and it ran perfectly, but I still havent put it back in the lake. Next weekend I plan to head out to the ocean with it? what is your feeling on this. Remember, it never overheated...it only ran to the high side of the guage for a couple of laps around the lake, and the lake is not very big. Tell me what you thinkn. Gregg

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