Nissan 90 problem

[PrplGld]

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

This motor is on a 16' Skeeter. It's been running great. Bout a week ago I got stuck in a bayou in a mass of water hyacinths. The way ahead was bad so I turned around. I was in the middle of the 65,000 acre Maurepas Swamp with spotty cellular reception so I pushed the motor to get the boat out. After about 20 yds of slowly trudging through the mess, I was just about in the clear when I noticed no cooling water was coming from the check port. I cleared hyacinths and hydrilla away from the motor and restarted, the motor was peeing again.

Went out today and the motor was running fine at first, although cooling water didn't come out of the check port for 5-10 seconds after first starting. Later in the morning I was heading back to the landing and the RPMs suddenly dropped. Couldn't get it to go much faster than idle. I limped backed to the landing at idle. The buzzer sounded 2 or 3 times earlier in the morning, I planned to take it to the shop and get it checked but now it will get there with much more concern.

I imagine the impeller might be damaged, or worse. Is there a feature in the motor that automatically lowers RPMs when the temp is too high? Any ideas?

Thanks for any help.

 

[TOHATSU GURU]

Re: Nissan 90 problem

There is a rev limiter that kicks in on low water pressure. Change out with an impeller kit and see what happens.

 

[PrplGld]

Re: Nissan 90 problem

There is a rev limiter that kicks in on low water pressure. Change out with an impeller kit and see what happens.

Ok, I'll do that and post the results.

 

[PrplGld]

Re: Nissan 90 problem

There is a rev limiter that kicks in on low water pressure. Change out with an impeller kit and see what happens.

Do I need a whole water pump kit or can I replace only the impeller?

 

[TOHATSU GURU]

Re: Nissan 90 problem

I would always recommend replacing with a kit due to possible wear on the liner and plate.

 

[PrplGld]

Re: Nissan 90 problem

There is a rev limiter that kicks in on low water pressure. Change out with an impeller kit and see what happens.

I found the owner's manual, it says revs will also be limited for an overheat condition. I just removed the lower unit and checked the impeller, it looks new. The rubber looks great, soft and rubbery.

I tried to remove the screen to check the water intake but the nut is slipping, I take it off later. What do you think?

 

[TOHATSU GURU]

Re: Nissan 90 problem

You can look at the rest of the cooling system to see if the issue is an obstruction, but...Kit the water pump first and try it. A worn plate, liner or impeller is still the most likely cause. If that doesn't fix the alarm it could be:

headgasket
thermostat
damaged block and/or piston
obstruction in the cooling system
bad ground on the electrical system
water pressure sensor
heat sensor

 

[PrplGld]

Re: Nissan 90 problem

I had a pdf file of an exploded parts view for my motor, can't find it now. Do you have a link for something like that?

 

[TOHATSU GURU]

Re: Nissan 90 problem

I have sent the parts book file to your email address.

 

[PrplGld]

Re: Nissan 90 problem

I have sent the parts book file to your email address.

Thanks!

 

[PrplGld]

Re: Nissan 90 problem

Later on the trailer, I looked under the cowling and found a loose black wire. There was a small black rubber cover over a round object with two blade terminals. Another black wire was connected to one of the blades and the top blade was empty, the loose wire had apparently disconnected from the empty blade.

That was earlier this year, in July. The loose wire was from the overheat sensor, as was correctly pointed out. I'm wondering if the previous owner somehow learned that the sensor was bad and disconnected it. I reconnected it in July but have only had the boat out for 3 short runs since.

I may replace the overheat sensor and the thermostat also $$$

 

[PrplGld]

Re: Nissan 90 problem

You can look at the rest of the cooling system to see if the issue is an obstruction, but...Kit the water pump first and try it.

Ordered it today. Got a great deal, and free shipping!