454 Bravo 1 engine overheats on first run only then works fine
07-20-2011, 01:53 PM
#21
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Since we're on this topic, I just had the same problem with my 87' 454 mag, she over heated but I wasn't so forunate to catch it so quickly. It pegged out at 250. I found the overheating problem which was a bad impeller, I also replaced the stat just to be safe.
Here is my dilemma now, after firing it back up she don't run right. I put in new plugs and wires but still no better. It doesn't seem like much exhaust is coming out of the pipe closest to the center of the boat and it sounds like it's out of time or loping/surging.
Any ideas???
Here is my dilemma now, after firing it back up she don't run right. I put in new plugs and wires but still no better. It doesn't seem like much exhaust is coming out of the pipe closest to the center of the boat and it sounds like it's out of time or loping/surging.
Any ideas???
07-20-2011, 02:57 PM
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Since we're on this topic, I just had the same problem with my 87' 454 mag, she over heated but I wasn't so forunate to catch it so quickly. It pegged out at 250. I found the overheating problem which was a bad impeller, I also replaced the stat just to be safe.
Here is my dilemma now, after firing it back up she don't run right. I put in new plugs and wires but still no better. It doesn't seem like much exhaust is coming out of the pipe closest to the center of the boat and it sounds like it's out of time or loping/surging.
Any ideas???
Here is my dilemma now, after firing it back up she don't run right. I put in new plugs and wires but still no better. It doesn't seem like much exhaust is coming out of the pipe closest to the center of the boat and it sounds like it's out of time or loping/surging.
Any ideas???
the question is going to be how long it was at 250 before you saw it... and if it caused any damage. only you have some sort of feel for that... especially if it was on its way DOWN when you saw it at 250... like all things like this you start with the basics... it ran well before this happened... now it doesn't. is there anything you could have done during the repair to screw it up ? wire knocked off, sensor broken, wires on in the wrong place... retrace your steps and look at all that stuff. if all th's correct then pull the plugs and look at them. that will tell you something... then do a compression check and leak down... those will tell you if any obvious damage.. etc etc... one thing at a time. eliminate all the big easy stuff then go deeper. that's all you can do. maybe it lost a head gasket... maybe it detonated and broke all the rings on one piston... maybe it did nothing at all... you need to get at it and do the basics first... like shoot the timing... why ? because if the timing was good before and its bad now, you might find the timing chain has jumped which i have seen during massive overheats for some reason...
you just have to dig in... oh... and look in the ends of the oil cooler for bits of that impeller...
07-21-2011, 02:43 AM
#23
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I have Mercruiser 454 with bravo 1 it's 1999 with only 55 hours on it, it was in storage for 6 years, last 2 times I took it out, the engine overheated to 210-220 then turned it off, I lifted the engine to check if the lower drive intake was plugged up but it was fine restarted and went back to 170 worked great for the next five days.
After 2 weeks I took the boat out and same thing happened, on the first run about 10 minutes the engine started to over heat I shut it off at 210 before the alarm went off. lifted the outdrive to check for blockage seems fine restarted the engine and went back down to 170.
Any ideas or advice what could be causing the overheating.
sam
After 2 weeks I took the boat out and same thing happened, on the first run about 10 minutes the engine started to over heat I shut it off at 210 before the alarm went off. lifted the outdrive to check for blockage seems fine restarted the engine and went back down to 170.
Any ideas or advice what could be causing the overheating.
sam
The alarm system and temp gauge are completely independent of one another.
I had a Gaffrig/Livorsi water temp gauge doing about the same thing you describe. The gauge would go to 220*+. I would shut it off for 2 seconds and restart and it would read normal.
The problem was the gauge and nothing else.
Last edited by Griff; 07-21-2011 at 02:45 AM.
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