ns40c 40 hp nissan dies please help

[jetties2003]

i just restored a 1957 14 foot starcraft ski champ and i installed a 1987 ns40c 40 hp nissan motor. it was a one owner motor and has always been in fresh water. i just took it out today for the first time and it worked fine except it dosent seem to have alot of power. i mixed the oil 50:1. it has a new battery. the motor acts like a 25 horse. it barely planes the boat. actually it feels like its not planing all the way. probly only 20 mph. the motor takes off fine but does not go very fast. it sounds good though. fires right up. after i run it at full throttle around the canals for about 15-20 minutes it dies. then if i turn the key right after it dies the motor barley turns over and wont start. after about 15 seconds it will barley fire up and the idle slightly rough. the motor makes it to the ramp at idle but if i try to accell it shuts off. seems like fuel. the water pump is shooting plenty of water and the motor never seems hot..... any ideas before i take her to the shop $$$$$$$$$$$$. we tried to wakeboard behind it and it really barley pulled me up and then was very slow. i have never in my life been able to have a boat that just ran. its driving me nutzzzzzzzz. anything helps... thanks. if i let it sit for about 20 minutes it runs good for a little bit but then does the same thing. seems like its getting hot but it does not feel hot

 

[Sea Rider]

Re: ns40c 40 hp nissan dies please help

Carb must be completely clean, check gas tank & engine gas filters for obstructions, check gas pump diaphragrams are in good working condition, check plugs if correct number as factory recommended, gapped tight to 1.0 mm, try a new gas hose, if all mechanical issues are ok, troubleshoot electrical parts...

Happy Boating

 

[jetties2003]

Re: ns40c 40 hp nissan dies please help

ok so i pulled the carb engine fuel filter and tank filter. all looked perfect but i still cleaned them. i pulled the jets out and the needle valve.bowl was very clean. everything is very clean. cleaned em and set them back in the carb. put a new fuel line and squeze bulb on it. plugs looked good and are the right part number. thermostat is working. took it out and tested it. just dropped the lower unit and the pump looks new and is nice and pliable. the water intake slits on each side of the lower unit do not have the screens in them. will this cause it to overheat. i ran it after i did all the work and it did the same thing but worse this time. the engine acted locked up but cranked right up and idled home after about thirty minutes. i just want to take my family for a boat ride..........also i pulled the fuel pump apart and it looked great

 

[jetties2003]

Re: ns40c 40 hp nissan dies please help

also i have the lower unit off right now. i went ahead and installed new o rings and gaskets on the pump. also replaced the shaft seal. should i use sealant around the pump. there was alot all gooped around it when i took it apart. thanks.

 

[Sea Rider]

Re: ns40c 40 hp nissan dies please help

the water intake slits on each side of the lower unit do not have the screens in them. will this cause it to overheat. i ran it after i did all the work and it did the same thing but worse this time. the engine acted locked up but cranked right up and idled home after about thirty minutes.

Replace missing tail water screens, motor could suck debris producing a great internal pump obstruction that can lead to severe overheating. For ending theoretical mechanical issues, how's head gasket condition, are gas pump check valves in order, well centered and closed tight against respective base ? If correct, seems your problem is electrical, buy a service manual and troubleshoot related electrical parts.

If that engine were mine and in excelent overall condition wanting to keep it, would buy a new or used ignition coil with caps, CD & exciter coil, if these parts still available being a 24 years oldie. Definitely one of the 3 must be the devil

Happy Boating