Runnin hot...bah!

[TheTinMan]

Pullin my hair out here. My 98 Merc 200 EFI gets an overheat alarm over 4000 rpm's. I replaced the waterpump, thermostats and the dealer did the poppet but still getting alarm >:(

I replaced a 15 psi water pressure gauge with a 30 psi one, 15 is too low for my motor. I also installed a Faria cylinder head temp gauge and sender.

I launched the boat today to run the Seafoam process....good stuff, try it! I needed to run the boat pretty hard after the Seafoam. Water pressure is WAY too high. The 30 psi gauge gets pinned at only 3000 rpm!

I did get her up to 50mph @ 5600 rpm ;).....and an alarm too! :'( :'( Temp gauge was only reading 145-150F. I really need one of those infra red thermometers that you just point and get a read on all cylinders to see if I'm actually running hot or not. Could just be a temp sensor maybe???

The really high pressure kind of points to the poppet valve not working properly. I have that pulled out and will take to the dealer tomorrow. If that doesn't fix the pressure problem I have a blockage somewhere. I'm hoping that's not the case because I really don't feel like pulling the power head and lower unit off.

Any Merc heads have any ideas? How bout you BigShrimpin?

Thanks

[spareparts]

i think you are on the right track with the sender, pull the sender out and float test it, replace with a new.

[msbhammer]

Sorry to hear of the high temps Tin, Hope it works out for ya.

[Airslot]

How old are the T-stats? They aren't that expensive, 12 each or so, might be worth changing out.

Airslot

[TheTinMan]

thanks, stats are new. :-/

[bigshrimpin]

Tin - My pressure at idle is about 3-5psi . . . 12 - 15 at cruise and 18 - 20'ish at WOT. 30psi is too high . . . something is wrong. I can't see the poppet causing pressure that high . . . Spares is the man here. There was a post about this on S+F a while back . . . about blown head gaskets causing some steam pressure.

http://forums.screamandfly.com/forum...ighlight=30psi

[spareparts]

if you want ot buy one of those temp guns, Harbour Freight has them for under $50. NAPA sells them for $75, They really are handy to have around. Other wise go to a welding shop and get some temp sticks, they look like a crayon, they melt at a prescribed temp, get one for 150, 175, 200, 225 temps, when your alarm goes off, stick it to the head and see which one melts. Your block pressure seems high, but not knowing the accuracy of your gauge( all instruments are subject to question), I would verify that you do have a heatiing problem first, tehn look at the poppit valve, theres not much in that block to restrict water flow other than the poppit valve. You may have a bad alarm module screwiing with you.

[TheTinMan]

While the head gaskets are definately a possibilty, I don't think so. A compression test should tell me that, correct?

I'm thinking it's an outlet obstruction now. I have a bad feeling I'm going to be removing the powerhead

[TheTinMan]

This is interesting too;

http://my.boatus.com/forum/forum_pos...amp;KW=225+EFI

[TheTinMan]

My thread over at "Scream"

http://forums.screamandfly.com/forum...d.php?t=120793