2 problems: temp guage/H20 oil

[rather_be_boatin]

Hello, I'm having 2 issues with my boat (99 Maxum 2400SCR, 220hp merc 5.0 2bbl), the 1st is the oil gets very slightly hydrated after a few hours of run time. Not enough to make the dipstick level increase but noticable. Upon close inspection it seems to somehow be sucking moisture in through the valve cover breather hose that runs to the carb. Has anyone heard of this? Is there a cure? My 2nd problem is an erratic temp. guage, it will rise slow, drop fast, go all the way to 280 and down to 0 than hold steady for awhile, buzzer never buzzes and verification with a temp gun indicates steady t-stat housing temp, steady riser temp. Impeller, risers, manifolds, guage, & sender are all new. I'm not sure weather to trust the thing or not, I've put plenty of hours on with this problem but would like to solve it. I'm baffled. Thanks in advance for any help.

 

[mkast]

Re: 2 problems: temp guage/H20 oil

Upon close inspection it seems to somehow be sucking moisture in through the valve cover breather hose that runs to the carb.

verification with a temp gun indicates steady t-stat housing temp

There is pressure in the valve cover, not vacuum, kind of hard to suck moisture with pressure.

What temperature is this engine running at? 280 to 0 ??? If the engine temperature is too low, condensation.

You state you checked engine temperature, with a temperature gun, you don't state what the temperature is.

 

[rather_be_boatin]

Re: 2 problems: temp guage/H20 oil

Oh, it was around 150(f) on top of the housing and 80 on top of the risers.

 

[paultjohnson]

Re: 2 problems: temp guage/H20 oil

Tryin' to picture how the breather hose could be sucking moisture ??? Is it cracked ? And yes there is pressure in the valve cover [tho slight] The hose connected to the carb does draw a vacuum. The PCV valve provides resistance to the vacuum draw of crankcase fumes untill there is enough RPM to create enough vacuum to pull crankcase fumes thru the pcv valve. Why do u feel moisture is getting in the oil thu that hose..?
As far as temp gauge, I bet you have a bad sending unit, or its not grounded properly. You didnt use teflon tape on the sending unit did you ?

 

[rather_be_boatin]

Re: 2 problems: temp guage/H20 oil

No teflon tape on the sending unit, and its new, acts just as old one did. These 2 problems may be related (like Mcast stated) if the temp is for real and I'm getting erratic temps, colder ones causing condensation? Or would the hotter temps burn it off? I'm going to test the (new last season) thermostat. Then verify flow through the power steering cooler, although the hose coming out of it, for cooling supply, is always nice and cool, about seawater temp. I'll do those 2 things and post results, although may not be for a week with my work schedule. The milky oil is most prevailant on the starboard side valve cover where the hose goes into the cover (most milky white at that location) and there is no PCV valve on that side, only on the port. (unless thats the problem, there should be a PCV valve on both sides?) That is what lead me to that being the source of moisture ingress. Thats about all I can think to do? I've been chasing this monster for 2 seasons now, very frustrating... Thanks for the help.

 

[paultjohnson]

Re: 2 problems: temp guage/H20 oil

Only 1 pcv valve I believe On the other valve cover there is air inlet. Looking at my old car right now. Opposite the pcv [positive crankcase ventilation ] valve is a air supply hose connected to the air filter assembly, with a small inlet filter installed. Fresh air is drawen into the valve cover, circulates thru the engine and is sucked out thru the pcv and pulled thru the combustion chamber and burned up...