94 200hp Mercury water temp high at idle

oledave

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Joined
Jun 29, 2011
Messages
3
I have a 94 Mercury 200 that I have replaced the temp gauge, T stat's which do not tell me the temp range, and installed a pressure gauge yesterday. I had another temp gauge that only read from Cold to Hot not very useful I wanted to know the actual temp so after installing it and the sending unit that came with it I have an idle temp of 170 water pressure is 2psi and the pee hole water stream is what I would call week.
After seeing the temp and psi I took the Tstats out and ran it with out them. Water temp came down to 130 water psi was about 1psi and the water stream from the pee hole was fantastic, but I called a buddy and he told me not to run it like this as the water needs to run down the inside of the housing across something he called an exhaust plate. So I put it all back like factory. Obviously the temp came back to 170 and psi stayed at about 2psi.

So then I clamped off the rubber water hose that travels from the center top of the engine down to the bottom of the block to something I think it is a poppet valve not really sure. This brought my psi up to 10 psi where I think it should be. water stream from pee hole is still weak.

What should the temp be at idle?
What should the psi be at idle?
What is a poppet valve and do I need it?
Where do I start looking from here?
I know these are alot of questions But I figure the more I ask the more I learn.
Thanks in advance for your intelligent feedback.
 

carholme

Rear Admiral
Joined
Sep 4, 2010
Messages
4,845
Re: 94 200hp Mercury water temp high at idle

Dave;

What is your engine s/n?

Gerry
 

oledave

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Joined
Jun 29, 2011
Messages
3
Re: 94 200hp Mercury water temp high at idle

Gerry engine # is OD 232279
thanks forgot to add that
 

carholme

Rear Admiral
Joined
Sep 4, 2010
Messages
4,845
Re: 94 200hp Mercury water temp high at idle

Dave;

That s/n comes up as:

MERCURY - (200 H.P. (1993 ))
Serial No: 0D232279 Model No: 1200412ND

Parts List for model 1200412ND:

135/150/175/200 XR6/MAG. III - Mercury, Mercruiser, Force, etc. Parts Lookup

Service Manual P/N: 90-824052R3

If you PM me with an email address, I can send you a copy of the service manual.

For the poppet valve question, see emckelvys response here. I couldn't explain it better than that.

http://forums.iboats.com/mercury-mariner-outboards/poppet-valve-function-364513.html

The only spec I can find for the water pressure is 12psi@5500rpm

Gerry
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 94 200hp Mercury water temp high at idle

Do not operate the boat with the T-stats removed, it may over-cool the motor and cold sieze a piston.

Test the stats in a pan of water on the stove, they should begin to open @ 138 and be fully open by 143

I suspect your new temp gauge is not accurate.

P stream is dependent on T-stat opening, depending on water temp and engine load they can cycle open/closed and the stream can come and go, a partial stream indicates a stat is only partially open, and can be if the motor is simply idling with no load.
 
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