Overheating and now blowing smoke...
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Overheating and now blowing smoke...

  1. #1
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    Default Overheating and now blowing smoke...

    Towards the end of last summer I noticed that my temp gauge was almost instantly pegging past the 250 degree mark.. I felt the exhaust logs and they were cool, hoses all felt cold so at that time (in my infinite wisdom) I figured I lost a ground wire or something and was getting a false reading...

    This summer got the boat all set after winter storage, while starting it up in the driveway I noticed that the temp was climbing fairly quickly but never pegged. Went out with the kids for a quick day of fun and she got realllly hot! what tipped me off was at one point some water dripped on the intake and it sizzled away in a steamy cloud ..

    Brought it home pulled all the hoses flushed the block and everything flowed fine (Fresh water only boat).. What I DID notice now was the overflow valve back in the bilge which I must have opened all the way at one point last year, which didn't allow for enough restriction to force the water through the block then out the overflow/exhaust....

    Temp was still higher than I would have liked, checked the oil (milky DAMMNIT), I just changed it this spring before our first trip out...

    I'm thinking I may have blown a head gasket, best case scenario based on the excessive overheating.. Worst case, cracked a head or part of the block...

    When the boat was running yesterday I could feel the heads, and both were cool to the touch, block both front and back was cool, center of the intake was actually fairly hot. At idle it ran fine, water flowing both through the exhaust and through the overflow on the drive. But when I raised the throttle to around 1500 - 2000 white smoke started blowing out the exhaust... At idle normal no smoke. Best I could tell was white (water) not blue (oil) but the oil is milky(ish) now...

    It's an early style SBC, from what I can tell pretty much stock with the addition of a high rise intake and edelbrock carb.


    What would you guys suggest as my first steps to diagnosing how much damage I did.. Figures it happens just at the start of our otherwise short boating season around here in Wisconsin..

    Compression test?
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

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  3. #2
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    Yes, blown head gasket!!!! If the engine got that hot it cooked the rings (loose tension), water in the oil will rust pit crank journals, camshaft and cylinder walls, etc. The engine needs to come out and all apart to save what you have. Hopefully it didn't destroy the block and or heads, etc.

    Good luck!

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    I'm hoping it is just the head gasket.. I can swap those out in a good day in the driveway.

    If the cylinders are not super smooth, and or scored think I could get away with just doing the head gaskets and praying for the best? Just trying to minimize downtime for the boat,, I do have another sbc that I could put in there but that would be another day or two worth of work.

    Are there any big differences between a marine head gasket and automotive head gasket? I see some that say they are for "Marine" engines but nothing really distinguishes why or what makes them different..
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

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  6. #4
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by steve_g View Post
    Towards the end of last summer I noticed that my temp gauge was almost instantly pegging past the 250 degree mark.. I felt the exhaust logs and they were cool, hoses all felt cold so at that time
    If your engine has a thermostat, replace it... may be stuck closed and bypassing most of the water out the exhaust
    Also, if you haven't yet, put a new water pump impeller in too.


    Quote Originally Posted by steve_g View Post
    ...what tipped me off was at one point some water dripped on the intake and it sizzled away in a steamy cloud
    Quote Originally Posted by steve_g View Post
    When the boat was running yesterday I could feel the heads, and both were cool to the touch, block both front and back was cool, center of the intake was actually fairly hot.
    If your intake manifold has an exhaust crossover, it will get pretty damn hot in the middle, even if everything is up to par. I wouldn't read too too much into it.


    Quote Originally Posted by steve_g View Post
    Compression test?
    Compression test is a good place to start. My guess is, it will simply confirm what you already suspect... which is the point anyway.
    No matter what, sounds like you're gunna end up digging into the engine. Hope it's simply head gaskets.

    Good luck!

    -Seth-
    Last edited by Budweiser; 06-15-2012 at 08:24 AM.

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    Thanks Guys,

    It does have the thermostat housing, but the person before I had the boat did something and while the "majority" of the thermostat is in there, the spring and plate to close off the flow was taken out,, basically I'm guessing just allowing freshwater to flow all the time.

    I did put in a new raw water impeller this spring as well and there seems to be plenty of flow out the exhaust and overflow.

    Here's a picture of the what I came up with when I was trying to figure out what the initial cooling problem was.

    Click image for larger version. 

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    I've also seen items like this from CP. I was thinking if I installed one of these, I could totally eliminate the "power robbing" circulating pump and have fresh water go directly into the block via the raw water pump, then come out the T-housing directly into the exhaust logs.. Would that be to much water going through the exhaust, I'm thinking the raw water pump would definitely pull enough water to keep up with the system,,, its the only thing drawing fresh water into the engine now.

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    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

  8. #6
    Or Seth, either one Budweiser's Avatar
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    Click image for larger version. 

Name:	boat_cooling.jpg 
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Size:	98.6 KB 
ID:	164634








    Last edited by Budweiser; 06-15-2012 at 10:16 AM.

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    Yeah, I know.. Its a HUGE rats nest under there... But I'm trying to do the best with what I inherited... Someone was REALLY creative when they plumbed this thing.

    Just because you can dosen't mean you should! ! this thing is a mess!
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

  10. #8
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    I'd LOVE to clean this up!

    With this being my first boat I'm not real sure where to start though.. I saw on the Glenwood site there was a diagram of how they suggest the flow to go..

    From the Raw water pump to the input of each exhaust log,, out the back of the exhaust to the inlet on the front of the block... Out the top thermostat housing to the exhaust dump.. Does that makes sense?

    Basically eliminating the circulating pump on the front of the engine where an automotive water pump would typically go...
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

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    here's a copy of what I saw that they suggest the plumbing to be..

    cooling flow.pdf
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

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    excuse me...just askin'...is this a jet drive or a v-drive?

  13. #11
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by FastRat View Post
    excuse me...just askin'...is this a jet drive or a v-drive?
    I'm assuming it's the one listed in his sig line.
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.
    Guess again... LOL
    Last edited by Budweiser; 06-15-2012 at 06:12 PM.

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    Sorry guy's,, yeah its a Volvo Penta out drive.

    Just out of curiosity, how are you guys running the water lines? Sorry if this seems like an obvious question but just trying to sort this thing out as best I can
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

  15. #13
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    So I did a compression test on the engine tonight after work just to see what I was getting at before I started pulling the motor apart.

    Here's the readings

    1- 79psi 2- 85psi
    3- 60psi 4- 75psi
    5- 75psi 6- 52psi
    7- 72psi 8- 80psi

    I used a screw in type tester no carb on the engine and it was cold. Those numbers seem a bit on the low side, but I have no idea when this thing was last rebuilt. 25% average of the highest reading would net me around 63.75 as a low from what I read online. Another thing I read was that you should start with #1 and crank (counting the number of times it takes to reach max psi) then use that same number of revolutions for each other cylinder. I didn't read that until after I was in and now its to dark to start again tonight. I just went until the pressure guage stopped climbing, should I retest tomorrow after work? Also going to try the wet test and add a bit of oil to each cylinder to see if the numbers change.

    Does it make a huge difference if this is done with a cold or warm engine?

    After pulling the plugs all were fairly dark (rich) except for #'s 5 and 7 which were a light brown. Could be the blown head gasket between those two cylinders that is causing the oil/water mix and smoke when throttled up?
    1982 Eliminator 21' Sport
    Chevy 350
    Volvo Penta 250 Outdrive.

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