water pressure alarm

[Ripple5]

hello all, I have a 97 Johnson 175 hp v-6 2 stroke on my Grady White and i'm having temperature issues. It seems the water temp pressure gauge moves fast like a tach and when it max's out at 30 shortly thereafter the HOT alarm go's off and the motor bogs down. Ok fine, replaced the water pump and both thermostats but got the same results I know there is a temp switch in each head or is the gauge bad and sending a false shut down to the motor ?Even when i ride over someone's wake the needle rocks a bit it starts right up ok runs normal, and the compression is good . the water pisser is shooting out the back fine and i always flushed after a salt water run. Thoughts ?? Thanks .

[Solarman]

Well when the over temp alarm goes off, carefully feel the water out of the pee hole, if cool them feel each side of the engine at the heads (bottom, middle, and top). If pee hole water and heads feel closely similar, then probably a bad sensor on one side?

Then if pee hole water is too hot to hold hand in, most probably so are the heads, and this means you have other problems. Maybe a blockage in the heads (could try running in large plastic trash barrel with ”salt away” for a couple hours), or possibly corrosion has allowed exhaust to enter water supply chamber slowing water flow rate? Maybe other corrosion issues? And maybe only have blockage in one of your six cylinders (a top cylinder) near one of you heat sensors?

So if water temp is cool you could still have one or more hot cylinder heads (be careful when feeling them by hand), a temp gun is the best way to go.

Good luck, let us know what you find out.

[Ripple5]

On seconed thought, when i was testing the water pump after install with a hose with ear muffs for a good amount of time the right side cyl head was cool the whole time and the left slowly got warm then hot to the touch. It was then i read up that there is senors on each. Hummmm. Is it normal for that (water temp pressure) gauge to react so quick ? in the past i noticed it mostly maxed out under high speed but never any issues. Thanks for your input.

[Solarman]

The water pressure doesn't set off the alarm, the temp sensors do. If one of your heads was too hot to touch, you probably have salt/corrosion blockage around that cylinder, or the pas-sages leading to that area. If running it in a large plastic trash can/ container big enough, and deep enough to fit your foot (with salt away, or vinager- 5-6gals) for a couple hours, or until the head temp is cooler to touch, then you might have to take the cover off that head to clean it manually.

Your temp sensors are doing what they're supposed to do.
Your pressure gauge tells you the water pump is pushing water, a good thing! By changing the impeller, it will push water, more better, also a good thing. That's why it's reacting better.

Flush the motor with a corrosion cleaner, it may fix your problem.

Let us know how it's going. Good luck.

[Ripple5]

Thanks, this all makes sence now. sounds like a weekend project. Will get back and report. thanks again.

[Ripple5]

*** ! Just got back from the water and what a comeback! I did what you said with flushing it out with SALT AWAY ( eight times in fact ) used the whole quart bottle 4 oz at a time with ear muffs. It foamed up big time running down the driveway but after a while with my red lazer temp gun i noticed both sides of the heads were starting to be close to the same heat. Replaced both heat sensors as well and double checked thermostats to be sure. I believe it was the flushing that did it. Also that pressure gauge moves slower and never gets above 15 as before it flashed right up to it's max of 30 under high speed. no doubt the passage ways were cloged and creating higher pressure. Thanks for your insight and ideas as to what could be wrong , I got my baby back and were making WAKES Thanks again. If you were a waiter i'd give you a HELL of a tip .

[Solarman]

Love the idea of a tip.lol

Just happy you're boating again. Keep a check of head temps for a little while. Flush motor thoroughly each time used. Salt buildup is a problem for all of us in saltwater.

Good luck, happy boating.