'92 Nissan NS90A - water pressure sensor

'92 Nissan NS90A (SN 3B7-1-15212)

Experiencing the limited revs problem once again. My motor wouldn't go over 2500 rpm. I think I'm finally down to a water pressure sensor problem. I took off the water pressure switch assembly and looked at the switch on the back. There's a light blue wire cut with copper exposed. The parts catalog only shows the ground and one other wire (the one currently connected is red, as can be seen in the first pic). Seem the parts catalog indicates that a light blue wire should be coming from the switch.

Should the switch maybe be replaced or adjusted? Is it wired incorrectly?. I'm not sure how to adjust it though. My mechanic can't get to it for 3 weeks. I checked the thermostat, there's no trash caught in it.

I'm wondering if the adjustment screw is set too low (bottom pic, without the black switch box).

Re: '92 Nissan NS90A - water pressure sensor

Nissan 90 hp running fine one minute then it drop down to 2000 rpm

1992 90 hp Nissan Outboard - rpms drop to 2800 and wil not come back??

90 Tohatsu alarm when in gear

It looks like the above threads are about the same problem I'm having. I suppose I could use some specific advice on adjusting the pressure switch.

Re: '92 Nissan NS90A - water pressure sensor

!/4 of a turn at a time until the sensor quits activating...If that is actually the problem.

Re: '92 Nissan NS90A - water pressure sensor

TOHATSU GURU said:

!/4 of a turn at a time until the sensor quits activating...If that is actually the problem.

Click to expand...

Ok, I wasn't sure if there was a measurement or I just needed to "eyeball" it. Correct, if it's the problem. Thanks.

I think the impeller was part of the problem. The kit I got from you made a very noticeable increase in flow from the check port.

Re: '92 Nissan NS90A - water pressure sensor

I'm still experiencing limited rpm's even after disconnecting the water pressure sensor and the overheat sensor. But then there's the oil level sensor. The buzzer stops, however, when I disconnect the water pressure sensor and the buzzer is supposed to sound with the oil level sensor.

So like an idiot I didn't have my manual when I had the boat on the water. Next I'll disconnect all the rpm limiting circuits and, according to the manual, if I'm still having the problem then I should replace the CDI unit.

I suppose you guys are wondering when I'll save some money and take the thing to a competent mechanic.

Re: '92 Nissan NS90A - water pressure sensor

Guru, I got tired of tinkerin with it and last week I took it to my certified Nissan mechanic in Gonzales, La (Jerry Lanoux). He says it'll be 3 weeks before he can get to it. I'll let you know what he says, just for sake of discussion. That diagnostic stuff is beyond my abilities.

Re: '92 Nissan NS90A - water pressure sensor

"That diagnostic stuff is beyond my abilities."

Sadly enough it's beyond a lot of certified techs ability today as well.

Re: '92 Nissan NS90A - water pressure sensor

OK Elvin, can you shed some light on this for me? Got my boat back, mechanic says the water pressure sensor needed adjusting and all 3 carbs were ridiculously dirty. He rebuilt the carbs, changed spark plugs, and replaced a fuel hose. I got it back in time to put it on the muffs, ran beautifully. Then I went out of town for 2 weeks.

I finally put it in the water yesterday. The motor started on the first turn of the key, warmed for 3 minutes, and idled perfectly. I then ran the boat about 1.5 miles down a canal and the motor sputtered when I hit the first idle zone. It sputtered for about 10 seconds and died, wouldn't start again. Turned over good though.

Got towed to a nearby pier and, to make a long story short, the boat sat for an hour. I came back to it and it fired up again, it idled really rough. Got out of the idle zone, still running rough. I eased up the throttle and felt what I can best describe as a light "bump" and the motor went from rough to smooth. Headed back to the landing at 4,000 rpm. It idled perfectly once back at the landing.

bad fuel, trash in the gas line, gremlins?

Re: '92 Nissan NS90A - water pressure sensor

Fuel system or electrical system...I would vote on the fuel system. The most likely culprit is contaminated fuel.

Re: '92 Nissan NS90A - water pressure sensor

TOHATSU GURU said:

Fuel system or electrical system...I would vote on the fuel system. The most likely culprit is contaminated fuel.

Click to expand...

OK, thanks. I'm gonna try it again in the morning instead of haulin it to the mechanic.