stevewix

i'm working on a 99 wellcraft right now with around 250 hours.

brought in because it runs hot- only on full throttle.
customer wanted to know more about the boat, so i started with a compression test. 7 cylinders were 120psi, +-3.
cylinder #5 was at 90 psi.

i'm hung up on what to recommend, boat has 240-280 hours (estimated); with one cylinder low, but livable (for a while anyways); should i even chase the cooling gremlin or yank the motor and start a rebuild?

it's a toss up in my book;
a. freshen the motor while it's in one piece,
b. hope it's ok and run it.

maybe tomorrow's leakdown test will tell me more.

until then, ideas?

MACDAD260

Compression should be between 150 & 160 on a healthy 502 Mag. Since all your numbers are consistently low, except #5, and the fact that the engine is low hours and runs good, I would recheck the compression with a different gauge and see how it compares to first check. Also, a leakdown check will help tell if you have excessive pressure loss. Your compression gauge may be off or the engine is ready to puke. Rings could be toast if the engine has been overheated. #5 could be a partial seizure. Good luck.

articfriends

iTrader: (1)

These guys are right,150-160 is more like what you want to see. If your gauge is correct you shouldn't waste your time or your customers money doing anything other than planning a rebuild.By the way,was hour meter missing or broke(estimated time?). Probably a 600 hour boat (the old "my hour meter was broke for a FEW YEARS!!)that someone sold the poor guy that currently owns it.

Big Boys Toys

The real qustion is why is it running hot???
How are the elbows on the manifolds, sea water pump impella etc.?
You would hate to toss money at it do a nice rebuild job and have the same problem!
Check the back inlet fitting coming in from the intermediate housing and make sure it is not corroded and filled with oxidation, I had a problem with that connection, Mercury used a tapered plastic threaded fitting that screws inside of the hose to make it tight, but over time if the boat owner does not flush oxidizes and starts to reduce the ID of the hose.
Boat will run at normal temperature up to 3500 then the temp starts creeping up as you increase rpm's. I think they may have had a recall on this I'm not sure.
Keep us posted on what you find!
Brian

cig1988

BBT, I had that problem a few years back and took while to figure it out. I am anal when it comes time to flush/wash etc and it still happened. Piss poor design on Merc's part.