Merc 90 HP 4 stroke Water Pressure

[wed]

I have a problem with water pressure gauge on my 90 Merc 4 stroke. How much water pressure should be indicated @ rpm and where should the gauge be hooked to?

New motor, good stream of water, no more than 5 psi pressure on gauge.

Got a service manual ordered but thought some one might have the information handy.

thanks.

[lakerunner]

Mine runs around 10 at idle and 30 at WOT. Look for kinks in line or some obstruction. Mine started bouncing around yesterday and I am pulling it from motor and trying to flush it.

[wed]

Thanks Lakerunner, that is more like what I would expect water pressure to be. I have had no more than 5 psi at any time, even after having it worked on by dealer. I will follow the sense line and check for damage.

thanks again.

[lakerunner]

I found my problem. Sat night we had a kinda bachelor party for a buddy and while out on lake at far end from home my battery decided to take a dump.

While trying to rope start the motor one of the guys I guess stepped on my wire and shift cable bundle and kinked my water tube.


OH and you can't rope start a 90 4stk Merc on the lake and I doubt on land either. Luckily my neighbor came and rescued us. He had one of those jumper packs. I will have one soon I know.

[wed]

An update on this issue. Dealer moved WP gauge connection several times with no change in pressure. I bought a service manual, did the research and found that Mercury has a water pressure gauge connection on the power head that is plugged from the factory. Had a little problem convincing dealer that the gauge should be hooked up here (they claimed that was for the smartguages). They ordered the special fitting (Leger), from Merc and installed it at no cost to me.

Tested it this past weekend (misting rain & 56 degrees) and it works fine. I get about 5 psi at idle and around 25 psi at WOT. Evidently the gauge must be hooked up to the specified connection on this motor for it to work correctly. Hope this info will be useful to someone.

I finally got some performance numbers on the 90 HP (break in done per factory spec). With just me on board, full tank of gas and about 150 lbs of extra stuff I got 39 GPS out of it. I was able to run 32 GPS with six adults, two dogs and the extra stuff. I am pretty pleased with this. The best I was able to get with the original 60 HP was around 25 GPS.

[lakerunner]

Glad you got it fixed

[brumbyvet.1044]

Wed,
Your performance numbers are almost exactly like mine so I guess we're getting the most out of our boats. I went thru the same problem with the water pressure gauge. Tracker marine had to order the fitting and they were backordered for two weeks. When they finally got it in and hooked up, I get about 5 psi at idle and 20 psi at cruise and above. Hope you enjoy your boat as much as we enjoy ours.

[mike]

wow, you guys are getting some great speed out of your 90's, what props are you running?

[brumbyvet.1044]

Mike, I'm running a Mercury Vengeance 13 1/8 x 16 SS prop. It turns 5900 rpm with full trim and one person in boat. Recommended top rpm range is 5000 to 6000 for this motor. With a boat load it will still turn about 5400 rpm.

[wed]

Mike - I think my prop is a 13.5 X17 but I am not absolutely sure. It is aluminum and one blade is already slightly damaged so I will be looking for a stainless prop soon. My boat props out at about 6100 rpm. I am able to turn about 5500 rpm with six people + stuff on board but it takes a while to get there. I thinnk Tracker got these boats dialed in pretty good.

OK, Tracker is currently NOT offering the NV logs for 2010. I called the factory because I was afraid there was some issue with the design. I was assured that there were no problems with the design and that the decision was a purely economic one based on our current economic climate. Evidently they did not sell enough of them.

Brumby - Good to hear the numbers confirmed and yes we have had a blast on the toon so far. I hope to make several more outings before weather gets too bad.

[dockholiday]

Hmm scratching my head. Running 16 and 17's on a 90. I started out with a 17p merc mirage and could only get 5300rpm with my 150. Dropped to the 15 enertia and got the rpm to the 5800 to 6000 range. Sure can't understand trackers reasoning not going forward with the nv logs getting those kinds of speeds from a 90. Sounds like a win win to me.

doc

[wed]

Correction - My prop is a 13.25 X 17 SOLAS aluminum. I had written it down but could not remember where. Acceleration is not great but it does move out pretty well when it gets up on the strakes.