I am trying to do a little PM on my boat I baught last July.

I don't think my temp gauge is working correctly ( tested by grounding out the Blue/Brown wire on the temp sender as suggested on another site) While reading articles and a few post, it appears I may be better off possibly if I installed a water PSI kit, then replace the temp gauge later.

I am looking for peace of mind and I don't think the Temp gauges are 100%, but If I can get a bench mark, then I will be able to notice changes in the norm for my motor.

Any thoughts or insight??

So far I have put in 2 new thermostat kits ( there where none installed ) Also rebuilt the Poppet valve and now have good flow. Impeller replaced last Aug.

Thanks.

psi first, no water it gonna overheat anyway at least with psi you know when it is circulating

That's what I was thinking too. I have come to have less faith in the Temp gauges reliability. If it's working I have at least a reference point. The PSI gauge at least would give my a bit more physical evidence, at least that's the way I see it.

Thanks for the thought

I have a psi guage on my 150 johnson and to be honest I am not sure what it should read. It is about 10 lbs at idle and 30 lbs at full throttle. My trim guage does not work. Should the pressure drop if I over trim the motor? Thanks.

Jake,

That's what I understand can happen if you over trim, I think it changes the water flow over the intakes. I have read where the drive was to short and that happening also. I'm guessing here, but it seems the flatter (or parallel to) the intakes are with the "rush" of water, the better the flow into the L unit will be.??

Jake, on my old Xpress boat if it was over trimmed water pressure fell off pretty far.

I personally either don't know how to read one well or just don't have much luck with them because trim gauges seem to be a waste on every boat I've had. I trim by steering feel and bow lift I suppose. When the steering is nice and light and the bow is up and boat is responsive it's perfect. According to the gauge though I'm still low.

OK, I have the PSI kit, Now I can't figure out which place to put it. Or better, not 100% sure mine has the "water by pass" or not

It is a 1991 mercury 135 V6, S# 0C283114


To double check, on top of my block is a 90* fitting, that would be the "water by pass" line??

Im with Slodsm, I trim by feel and conditions. I also know when I hear the motor hit that nice hollow sound, im in the sweet spot.

I am looking to hook up a PSI gage myself. Last time out, the water was shallow and I went through a bunch of mud. The telltale stopped working. The heat alarm did not go off, but it woried me. A lot of times when the alarm goes off, it can be too late. I made it back in and found the motor was fine, there was just mud clogging the hose to the telltale.

To me the only time a trim is gauge is useful at all is timming down going through a NO Wake zone like a bridge. I talked to my mechanic about temp gauges and he said they are good on I/Os but on an outboard he thought they were not real reliable. PSI is the way to go. On my Merc there was a plug on top of the motor on the starboard side that I replced with the fitting from the PSI kit.

OK, found it. On my motor (merc 135 v6) there is a water by pass on top. the 90 degree fitting with the hose running to the Poppet valve. Found it on the DIY site, so all mounted and tested for leaks.

Easy job too!