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

[jhbau1000]

1991 Nissan 90 hp running fine one minute then it drop down to 2000 rpm and will not go any faster. Anyone have any ideas what could be doing this.

 

[TOHATSU GURU]

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

Just about anything. You have to troubleshoot the engine to determine if the problem is related to the ignition system, fuel system or if its mechanical.

 

[jhbau1000]

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

also, I have put in a new water pump new water pressure switch. I have water coming out the check pipe just not enough to turn the buzzer off. I hooked up a water hose to the hose on the check pipe to see if something was stuck in there and I have water come out the water pump tube when I put my finger over it water starts comeing out the exhaust is this normal.

 

[TOHATSU GURU]

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

You have completely lost me.

 

[jhbau1000]

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

Sorry about that but I?m having a low water pressure problem too thought that it may be why I'm losing rpm. Do you know if the water pressure switch
Is just a on or off switch or does it have to reach a perceive Ohm to keep the low speed ESG from coming on. When water is applied and all know water ports is blocked off water comes out the exhaust.

 

[TOHATSU GURU]

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

The pressure switch sends a signal to the warning buzzer. It will in no way cause the engine to drop RPM's. (Yes, it can) Water is supposed to come out through any and all exhaust ports. If your cooling issue is causing the engine to drop RPM's it can only be from the engine seizing up due to heat.

 

[jhbau1000]

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

Its not seizing up it runs fine and the drop in rpm is not all the time.I had it out saturday it ran all day at 4900 rpms sunday it ran to fist fishing hole just fine but after that it was down to 2000 rpms the rest of the day. But this not the frist time it done this (about 2 days out of 5). When it drops it still run fine purs like a kitten just will not due over 2000 rpm.

 

[jhbau1000]

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

p.s. it started doing this when my water pressure warning buzzer started going off so I put all new parts in the water pump and I still have water pressure warning buzzer going off but I get good water coming out the check hole just not enough to turn the buzzer off so I disabled the water pressure switch

 

[TOHATSU GURU]

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

The pressure switch is adjustable...Look on the back of the switch.

 

[rogerwa]

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

I don't have my manual here right now but could this be kicking in a limp mode?? In reading my manual I know there are a couple..

I'll get my manual later and check it out..

 

[TOHATSU GURU]

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

The CD limiter section will kick in for an over rev, low oil or water pressure signal. But, it does not drop it down to 2000. The limter will drop it down to the 3000 to 3200 range.

 

[jhbau1000]

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

Yes I?ve tried to adjust the switch no luck still will not turn off buzzer. I will look in my book I thought it said that it would drop down to 2300 rpm?s on water pressure warning and give buzzer and lamp only on low oil.

 

[TOHATSU GURU]

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

My manual doesn't say anything at all....But, I remembered it as the limiter only coming on if you were exceeding max RPM's and that it would drop you down to 2500. I also remember that the limiter would not activate on low oil or low pressure. However, I brought up your situation with Tohatsu earlier today and was told that the 90A2 models did have a limiter for all three of the conditions and that it would drop it down to the 3000 range. I'm not sure I was wrong to begin with and I will ask someone else there tomorrow to double check.

 

[jhbau1000]

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

Thanks any help would be nice but I may have found the water leak I pulled the power head to put the lock rubber on since I had one on hand and the engine base gasket is blown at the exhaust side that faces the water tube.

 

[jhbau1000]

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

My book says

Abundant number of safety devices
1: Neutral switch
2: Safety switch
3: ESG (Overrun preventing device)
4: Overheating alarm buzzer
5: water pressure sensor ( Capable of instantly alerting operator regarding a clogged cooling water inlet port)
6: Oil level sensor (Lamp & Buzzer)
7: Engine protection system : Lowers engine speed below 3,200 rpm through the operation of low speed ESG in case the water pressure sensor is activated.

It does not say what it will drop to just somewhere below 3,200 rpm's now I remember one day it drop to 2500 rpm's so the ESG may not be very accurate
and it just lowers it to a good running speed range.

 

[TOHATSU GURU]

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

And the final word is as follows:

The ESG will kick on for low pressure, overheat and over rev. In theory, it will drop it down to the 3000 RPM range....

 

[jhbau1000]

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

Is the ESG built into the CD unit

 

[TOHATSU GURU]

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

Yes, it is.

 

[jhbau1000]

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

Is there any way to test the CD unit do not won't to just replace it it's over $300 for a new one.

 

[TOHATSU GURU]

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

Yes, The test procedure is in the service manual. It's involved, but the tests are accurate.