relaxalot

I have the 600sci with the XR. One thing that really increased the pressure is we plugged all of the vertical holes in the drive except for the bottom 3. We drilled the 4 nosecone bullet holes out slightly oversize. I think that as the rpms increased and the outdrive was lifted out of the water perhaps the top holes were not even in the water thus reducing pressure. My problem was solved by feeding the intercooler with the external pickup and plugging the vertical holes. The boat is a Howard sportdeck (cat hull with a small center pod) I also heard that since the 600 water dumps back into the headers that if the motor has mufflers (mine does) this can cause a problem of too much backpressure setting the boat into guardian. Temp and pressure are definately intertwined.

US1 Fountain

iTrader: (1)

Are the inlet hoses from the transom assembly to the seawater pump of the reinforced type? (wire within the wall) A regular hose has no strength to it and will suck flat when used on the the inlet side of the pump.

racer-x6

Yes it is reinforced type. I called Mercury and they were no help, he says sounds like you tried everything I would have.

Any thoughts on the restriction before or after the pressure guage?

US1 Fountain

iTrader: (1)

I agree with your gauge reading location thought. Blockage afterwards= higher pressure.

Have you considered reading at the block itself to narrow down the problem location?
All your coolers were back flushed?

I assume you mean you have a 'closed' cooling system in the original post, not fresh water??

US1 Fountain

iTrader: (1)

Not following, what hose are you talking about? The one on the outside of the transom that is tucked in behind the bell housing, or on the inside going to the SW pump?

articfriends

iTrader: (1)

Whats wrong with 14 psi,its all I have ever seen even at wot? Smitty

racer-x6

Correct, the motor is closed cooling that is why I moved the water pressure from the block to the tose just after the power steering cooler as shown in the first post.

yes the one behind the bell housing, I ran it from one side under the motors to the other side (port drive to starbord motor and starbord drive to port motor) and the problem followed. the only other hose is the molded one in the drive and I replaced it. the ond one looked fine. I replaced all the orings and the housing is clear. the bottom of the boat has had nothing added.

when I ran it saturday it was down to 10-12 psi at 4000 and the starbord was at 24psi.
I think I can rule out anything with the motor since it is not loosing any fluid or adding any sea water. the oil looks fine also. Even the exhaust headers are on the closed cooling system.
Just to recap, water enters the low water pick-up, flows through the drive---- through the transon assy.---1-1/4" hose to the water pump-----power steering cooler-----fuel cooler----oil cooler--------into the heat exchanger---------out to the tail pipes. the water pressure is inline between the p/s cooler and the fuel cooler.

racer-x6

anything above 3500 the oil temp goes up and the water pressure starts to drop. If I hold it the water temp will start to go up.

US1 Fountain

iTrader: (1)

Seems like you'd be looking at blockage in the drive itself, in the molded hose that is routed on the outside that fits in the groove in the transom assembly or in the plastic fitting that seals that hose to the transom assembly. Have you verified the molded hose on the outside is indeed located in the groove and not pinched when the drive is lowered/trimmed? Also not twisted?

Have you ran water backwards thru the problem area?
Just a simple wire poked thru the hoses to check for blockage probably isn't an accurate test.

Is this a new problem that just happened? What did you change when this happened?

Not familiar with closed cooling systems to know the ideal pressures.

No other ideas comes to mind.
Good luck!

cig1988

http://www.mercruiserparts.com/Show_...Gimbal+Housing

Pull off #20 on both sides. Compare the opening from the good side to the problem side using a deepwell socket. Not sure what size socket but "fit" the good side first. Trust me I had this problem a few years back & drove me crazy for weeks. Usually when you remove #20 chances are good you will see white colored corrosion around the inlet hose.
This problem can also follow into the outer bellhousing where the driver bolts to.