1992 Nissan NS90A alarm at low speed, Dies above 3/4 Throttle

[EastsideMidge]

I have a 1992 Nissan 90 HP outboard. Lately it has been having issues with running with the boat on plane, anything above 1/2 to 3/4 throttle will kill the engine. It acts like it has the fuel cut out. bogs and stalls. It can sometimes recover by returning the throttle to neutral, sometimes it does not. Usually it will restart, but it cranks slow. Last time this happened, the motor would not restart and I pulled the boat until it can be resolved. My initial impression was it may be a fuel issue, starving for fuel at the upper end of throttle, but I am starting to second guess myself after reading threads about the water pressure switch. I was getting an alarm at low speed that would clear up after 1/4 throttle. I am wondering now if the engine is getting hot under load and cutting out via the high temp sensor or the pressure switch. Any help or opinions are appreciated. I am not sure on the theory of operation of the high temp cutout and water pressure switch, if they could cause an issue like this. I do not have factory Tohatsu/Nissan gauges to indicate whether the motor is getting hot.

For reference, I am running a new-ish fuel line and primer bulb, new-ish aluminum 12gal tanks (2yr old for both) which have not given me issues in the past. I installed an impeller last year. The impeller may have had an extended out of water run event, and is going to be replaced ASAP along with the thermostat. Also on the list is a link and sync. I currently have a factory service manual as well. This is a freshwater boat.

Thanks for any help.

 

[alldodge]

Welcome
Never worked on a Nissan but your getting an alarm and then the motor starts to die. Need to do some testing

Did find that the Nissan is actually a Tohatsu just rebaged

Crank slow can come from a weak battery, bad connections or the motor is over heating. Take a IR temp gun and measure head temp under 1/2 throttle and what happens above that

Don't think it's fuel because there is an alarm and it's 2 stroke

 

[Arky86]

I have a 1992 Nissan 90 HP outboard. Lately it has been having issues with running with the boat on plane, anything above 1/2 to 3/4 throttle will kill the engine. It acts like it has the fuel cut out. bogs and stalls. It can sometimes recover by returning the throttle to neutral, sometimes it does not. Usually it will restart, but it cranks slow. Last time this happened, the motor would not restart and I pulled the boat until it can be resolved. My initial impression was it may be a fuel issue, starving for fuel at the upper end of throttle, but I am starting to second guess myself after reading threads about the water pressure switch. I was getting an alarm at low speed that would clear up after 1/4 throttle. I am wondering now if the engine is getting hot under load and cutting out via the high temp sensor or the pressure switch. Any help or opinions are appreciated. I am not sure on the theory of operation of the high temp cutout and water pressure switch, if they could cause an issue like this. I do not have factory Tohatsu/Nissan gauges to indicate whether the motor is getting hot.

For reference, I am running a new-ish fuel line and primer bulb, new-ish aluminum 12gal tanks (2yr old for both) which have not given me issues in the past. I installed an impeller last year. The impeller may have had an extended out of water run event, and is going to be replaced ASAP along with the thermostat. Also on the list is a link and sync. I currently have a factory service manual as well. This is a freshwater boat.

Thanks for any help.

I have the same engine and am having the same problem. Hoping to get some answers off your post. I have replaced the fuel pump, all the fuel lines, the spark plugs, and the primer bulb thinking it was a fuel issue as well. After mine dies it doesn’t want to idle. Hopefully we can get some answers! I can putt around in mine all day with zero issues, but like yours at 3/4 or more throttle after a short time it dies.