spike in water pressure

DuckDogTitus · Posted: Mon Jul 21, 2014 11:58 am Post subject: spike in water pressure

what would cause a sudden spike in water psi? the motor is a 90hp merc. while cruising from Blakely to FH suddenly the alarm went off and PSI spiked to 15+psi. I shut everything down and switched to kicker while I could inspect. the motor never overheated and I couldn't find any problems. a gave it a few moments, fired it back up and the problem did not repeat.

I did some reading on poppets being stuck open or closed, but I'm not really familiar with what the poppet is in the first place.

potter water · Posted: Mon Jul 21, 2014 1:17 pm Post subject:

Hmmm. I didn't know that merc's had a water pressure sensor or display. What year is the motor? I owned a 1999 merc, and it had nothing like that. I don't even know why water pressure...in the cooling circuit I presume...would even be sensed or displayed somewhere.

Aurelia · Posted: Mon Jul 21, 2014 1:20 pm Post subject:

Sounds like temporary cooling water blockage if the PSI is for water. Nice to have such a gauge when normally you just get an overheat alarm a few minutes later.

Greg

DuckDogTitus · Posted: Mon Jul 21, 2014 1:24 pm Post subject:

its a 2005 model 90ELPTSW4.
I got the alarm one other time when I realized we went through a nasty kelpy area in rip coming out of bellingham last year. It was the first time I had heard such a thing so I shut everything down and investigated, the motor was wrapped in seaweed. I cleaned it and we were underway again. i did not however notice any difference in PSI (that time) but didn't look. I was concerned about heat.

this time, when i shut everything down I raised the motor and did find a bunch of kelp came off, so the possibility is the same. but what's odd to me is I thought that psi would more likely DROP if there was a clog from vegetation... not increase.

either way everything seems to be fine and I ended up boating another 30-40 miles after that with no weird instances in heat or psi....

DuckDogTitus · Posted: Mon Jul 21, 2014 1:26 pm Post subject:

I just wanted to see if there was anything to be concerned about. I'm planning on taking the wife to Sucia and West Beach in a couple weeks and I want to make sure everything is in tip top shape. the drive alone is about 2-3hrs for us just to the launch, so its a trip.

Bill K · Posted: Mon Jul 21, 2014 3:58 pm Post subject:

I have a water pressure gauge on my 90 Honda and it tells me my water pump is working ok.

I would take a piece of weed eater cord and feed it into water tell tail outlet the next time you get a pressure spike.

Something plugging the outlet is the only reason I can think of for the pressure to spike.

Bill Kelleher

redbaronace · Posted: Mon Jul 21, 2014 4:16 pm Post subject:

thataway · Posted: Mon Jul 21, 2014 4:21 pm Post subject:

Most likely a little piece of debris-as when you went thru the kelp bed. It is also nice to have an IR thermometer on board--that way you can check a number of areas on the accessible parts of the engines--and see if there is localized heating.

95% chance this is OK--and it is not worth looking for that other 5% since it cleared up in short order.

DuckDogTitus · Posted: Mon Jul 21, 2014 5:50 pm Post subject:

interesting, thanks for the feedback guys. I really thought that a clog would have caused the opposite reaction and a drop in pressure.

and in regards to the fuel prices... yes I'll probably top off before we go, but even on Blakely the fuel was about the same-ish. $5.30 or $5.39 if I recall correctly...

digger · Posted: Mon Jul 21, 2014 9:39 pm Post subject:

The kelp could have sent debris through the intake, slightly plugging the discharge pee hole, while also starving new water from entering the engine. That is why I installed the pressure gage to alert a person prior to an alarm...however, usually you only see the pressure change after you hear the alarm and start looking for the problem. I try to look at the gage when I know I went through some debris -- usually, a pressure drop indicates a plug. Most of the boat shops I spoke to wondered why I would want a pressure gage -- that is the reason. Also, sometimes getting debris off the prop is as simple as putting the engine in reverse and giving it a little throttle.