Not so good find on my 502 MPI
03-14-2019, 06:48 AM
#12
Registered
x2,,use cometics gaskets and it won't leak there anymore.sen plenty of felpro's leak like that,not so much on the graphite coated gaskets ,until they get old.
03-14-2019, 07:07 AM
#13
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This is a factory-sealed motor so it has whatever came on it in 1999. The starboard motor has had the top end done. From what I can tell so far, the starboard motor is fine.
03-14-2019, 09:03 AM
#16
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Yep, twenty years is beyond great! A new motor wasn't quite in the budget for this year, but shi!t happens. I have a tendency of leaning toward the less than dark side of things when this stuff happens. I'll try to remain optimistic; I haven't been well enough to spend any real time on it so we're only seeing what's on the outside. I'm hoping to have some time this weekend.
TZ
TZ
03-15-2019, 09:27 PM
#18
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Nothing much to update.
Looked at it a little more tonight. I got the intake off, and I’m down to removing the heads.
The block is corroded but not too bad. I think it’ll live. On inside it looks like a new engine.
I have been thinking about swapping out the injection for carbs, and also doing a valve train update. Since it’s apart this far, it may be time. I’ll probably just leave it, but I have thought about it.
Looked at it a little more tonight. I got the intake off, and I’m down to removing the heads.
The block is corroded but not too bad. I think it’ll live. On inside it looks like a new engine.
I have been thinking about swapping out the injection for carbs, and also doing a valve train update. Since it’s apart this far, it may be time. I’ll probably just leave it, but I have thought about it.
03-15-2019, 11:44 PM
#19
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TomZ
Here's some info. I had the same problem. Solved it using the Mercury 863204A3 pressure regulators. Expensive but worth every penny.
Here is a thread from OSO a few years ago.
Pressue relief valves?
Especially read the comment by MOP.
Here are some comments from me way back on OSO
"502 HEAD COOLING WATER SEEPAGE FROM HIGH WATER PRESSURE. Replying to MOP's old post about the PRV's on cooling water pressure.
These PRV's from Mercury Racing are an engine saver. Expensive but worth every penny.
After reading for a long time on OSO on a lot of articles about 502 head leaks there was one knowledgeble gentlemen that had been around for awhile and said if you are running more than about 20 or 25psi that you would most likely see corrosion/leakage on the outboard side of the heads. Sure enough, i had both heads both motors with corrosion at the gasket and rust on the block below the gasket line.
Bought these PRV's from Mercury and ALL of the seepage stopped completely. Thanks for this one gentlemen's comments. Wish i could remember i would thank him. These PRV's have never stopped up or failed to hold exact pressure.
I actually went out and found a lighter spring that fit, and ground the OD a little bit more to reduce the set pressure on the factory Merc PRV from 30psi to 15psi. The blockpressure runs higher though. - was actually about 5psi higher i presume from the circulating pump at higher rpm.
Ended up with about 20psi in the block which is where i wanted. It." END
These should help. You can always take them off and use on the next boat.
Mercury 863204A3
Here's some info. I had the same problem. Solved it using the Mercury 863204A3 pressure regulators. Expensive but worth every penny.
Here is a thread from OSO a few years ago.
Pressue relief valves?
Especially read the comment by MOP.
Here are some comments from me way back on OSO
"502 HEAD COOLING WATER SEEPAGE FROM HIGH WATER PRESSURE. Replying to MOP's old post about the PRV's on cooling water pressure.
These PRV's from Mercury Racing are an engine saver. Expensive but worth every penny.
After reading for a long time on OSO on a lot of articles about 502 head leaks there was one knowledgeble gentlemen that had been around for awhile and said if you are running more than about 20 or 25psi that you would most likely see corrosion/leakage on the outboard side of the heads. Sure enough, i had both heads both motors with corrosion at the gasket and rust on the block below the gasket line.
Bought these PRV's from Mercury and ALL of the seepage stopped completely. Thanks for this one gentlemen's comments. Wish i could remember i would thank him. These PRV's have never stopped up or failed to hold exact pressure.
I actually went out and found a lighter spring that fit, and ground the OD a little bit more to reduce the set pressure on the factory Merc PRV from 30psi to 15psi. The blockpressure runs higher though. - was actually about 5psi higher i presume from the circulating pump at higher rpm.
Ended up with about 20psi in the block which is where i wanted. It." END
These should help. You can always take them off and use on the next boat.
Mercury 863204A3
03-16-2019, 08:00 AM
#20
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Cap’m,
Thanks for the insight!
I’ve always had concerns about the water pressure. At speed she would peg 35 PSI. I went with aftermarket impellers to lessen the pressure, but it had not made a lot of difference.
I asked the previous owner about it, and he said he’d never known it ran that high until after he installed pressure gauges. He figured after running all that time without issues, there was nothing to worry about.
I have some pressure regulators sitting in the tool box. I made them last year from parts I picked up from CP Performance. I guess it’s time to put them in.
I would encourage other 454/502 MPI owners to keep an eye on this. The problem stems from the new style thermostat housing that came on raw water-cooled versions.
Thanks for the insight!
I’ve always had concerns about the water pressure. At speed she would peg 35 PSI. I went with aftermarket impellers to lessen the pressure, but it had not made a lot of difference.
I asked the previous owner about it, and he said he’d never known it ran that high until after he installed pressure gauges. He figured after running all that time without issues, there was nothing to worry about.
I have some pressure regulators sitting in the tool box. I made them last year from parts I picked up from CP Performance. I guess it’s time to put them in.
I would encourage other 454/502 MPI owners to keep an eye on this. The problem stems from the new style thermostat housing that came on raw water-cooled versions.
Last edited by TomZ; 03-16-2019 at 08:48 AM.
