ZT280

So here's the deal, this year I noticed a lot of steam coming out the exhaust tips (steam, not smoke). It's a '99 502 EFI. Last year I shredded an impeller. Pulled a bunch of large chunks out from the raw water pump, but smaller pieces circulated through the cooling system. I run through a PS cooler, fuel cooler and then an oil cooler before flowing into the thermostat housing. I pulled the hose off the bottom of the oil cooler and found what I thought was the rest of the shredded pieces packed solid on the honeycomb grate on the bottom of the oil cooler. Ran it the next weekend with no steam, all seemed fine. Now yesterday I was steaming again, mostly out of the starboard exhaust tip. I checked the oil cooler grate again - nothing. I ran the boat with the hose off the bottom of oil cooler and seemed to have good flow, so I'm thinking there's nothing blocking the system between the raw water pump and the oil cooler.

Could something have gotten past the oil cooler? Could there be some blockage in the starboard manifold or riser?

The manifolds and risers are only a year old, and the temp never got over 175, even before I found the old pieces.

Any thoughts on this?? I don't have a water pressure guage.

ZT280

any ideas??

Griff

Anything is possible, but pieces small enough to get past the oil cooler will just run through the entire system. Use a laser temp gun and take temp readings off each riser to see if there is much of a difference.

Ted G

iTrader: (1)

If you didn't replace the housing when the impeller failed it could be scored up, which will markedly reduce water flow.

ZT280

Thanks guys, here's an update...today I pulled the water pump housing (the housing was replaced along with the impeller last year) and it was fine. However, the hose feeding it was fraying quite a bit and could be impeding water flow. I also pulled the riser off the starboard side, water jackets seem good and I filled them from the bottom of the manifold and they held their water level, so they're not leaking. The gasket is real tough to tell since I basically destroyed it taking the riser off. I'm going to bring what's left of it on the riser to my local marina and see what they think. One thing I did notice though is that the end of the riser that goes into the pipes was painted. The paint has peeled off substantially and definitely looks like it could be blocking the flow of water out of the water jacket discharge. Anyone ever hear of this? To the touch the manifolds didn't feel too hot, but if the blockage was at the discharge then I imagine they wouldn't. I'm hoping the steam is from the water that actually is getting through hitting the hot exhaust pipe. Thoughts?