1987 nissan 25hpruns great out of water but put under load rev or forward when throttling its missing but at idle its ok?

[terry alvis]

1987 nissan 25hp runs and trottle great but in water under load it misses when throttling in forward or rev. then dies, but will idle perfect. tired of pull starting it

 

[Sea Rider]

Welcome to Iboats,

To start with has the carb been serviced lately ? Was the tank's air vent opened, what about the fuel hose, is it the original that came with the motor ? Will the motor miss same when throttling say 3/4 to full grip and start right up whan has cooled for say 5 minutes ? As you have witnessed running a motor without load it's a different scenario that running pushing a boat at load.

Happy Boating​

 

[pvanv]

Yep. Verify fuel system from tank strainer to carb and clean the carb properly. Then re-test.

 

[Sea Rider]

The OP's motor. seems to have the same issues as the 30 HP I'm looking after, except the later doesn't die after missing, hesitating, misbehaving, whichever such symptom it's called. Have had related issues with fuel hoses sucking air through the connector's o'rings when more fuel it's in demand at higher speeds.

Happy Boating​

 

[terry alvis]

Welcome to Iboats,

To start with has the carb been serviced lately ? Was the tank's air vent opened, what about the fuel hose, is it the original that came with the motor ? Will the motor miss same when throttling say 3/4 to full grip and start right up whan has cooled for say 5 minutes ? As you have witnessed running a motor without load it's a different scenario that running pushing a boat at load.

Happy Boating​

yea serviced the carb, put clear fuel hose on to see what happening, cleaned tank out ,took it it idles perfect but when i gave it gas in forward or rev you can hear it missing, but i just replaced the fittings on fuel tank and motor fitting i did away with and put barb fitting so fuel will go straight to filter then pump then to carb. seen alot of air bubbles from tank side thats why i replaced fitting , now waiting for good weather.will air bubbles cause it miss when throttling?

 

[Sea Rider]

Air bubles entering the carb through any of both connector's o'ring could make the motor to miss, hesitate at say 1/2 to full grip, depends on how worn out were the O'rings condition. Report if the issue was solved on your next outing, good luck!!

Happy Boating​

 

[terry alvis]

yea serviced the carb, put clear fuel hose on to see what happening, cleaned tank out ,took it it idles perfect but when i gave it gas in forward or rev you can hear it missing, but i just replaced the fittings on fuel tank and motor fitting i did away with and put barb fitting so fuel will go straight to filter then pump then to carb. seen alot of air bubbles from tank side thats why i replaced fitting , now waiting for good weather.will air bubbles cause it miss when throttling?

Just got boat out, finally good weather but it still running the same, in neutral-great. But put in forward or reverse it misses, it can only go at half throttle before it would bog down and DIE but would start back up on first pull. I serviced carb ,blowed out all air passages, new clear fuel line and fittings, primer bulb. Thinking about a NEW TANK? Look inside old one, it looked good, pickup tube and all. I'm still seeing big air bubbles sometimes when I leave air vent open all night. Any suggestions?

 

[Sea Rider]

If the carb was cleaned to a spotless condition, seems definitely an electrical issue. Check the spark with a spark tester at a dark place, the spark must be bluish, bright and strong. Ignition Coils fail over time specially after 33 years of use...

Happy Boating​

 

[terry alvis]

If the carb was cleaned to a spotless condition, seems definitely an electrical issue. Check the spark with a spark tester at a dark place, the spark must be bluish, bright and strong. Ignition Coils fail over time specially after 33 years of use...

Happy Boating​

everybody says fuel issue but iam wondering also , electrical. either coil or cdi unit? can either one or both be checked be checked with voltage tester? i also put new plug wires on also.

 

[MattFL]

Fuel issues and electrical issues can give very similar symptoms. To rule out fuel; if the carburetor is clean, make sure any under the hood fuel filters are clean and run it on a portable fuel tank. Squeeze the bulb and make sure it's tight when you have the issue. If squeezing the ball fixes it then you might have a fuel pump issue. If the ball stays hard and the problem remains then it's likely electrical.

 

[Sea Rider]

You replaced both fuel connectors ar both sides ? if yes, both o'rings are brand new. What's the condition of both male fittings where both connectors connects to, are they smooth to touch with no scratches whatsoever ? The fuel pump on those are heavy duty ones, the diaphragams are mylar made, a though plastic film, has nothing to do with rubber ones that balloons real fast with E fuels.

The fuel pump is mounted with two side screws on to a rectangular gasket, with a scredriver adjust both tight, if bit loose the fuel pump will not work as it should as air could be entering there and loosing vacuum. Prime bulb with arrow facing upward till firm, disconnect the carb's fuel entrance, put hose into a container, start the motor at idle/meutral and check if there's a strong fuel flow. Can do it while flushing on muffs. Check both to rule fuel system issues, which I doubt.

You need a good analog meter DVA capable or a digital one and a auxiliary DVA converter. Check this related thread : https://forums.iboats.com/threads/which-one-is-best.743294/

Will anticipate that sometimes both tests could end up in being useless if the electric component to check shows good under such tests, but with erratic electrical behaviours when heating up which are the most complex to troubleshoot fast. Better be a failing Ignition Coil which is cheap, the CDI on those costs a whopping + 250 bucks.

Happy Boating​

 

[terry alvis]

You replaced both fuel connectors ar both sides ? if yes, both o'rings are brand new. What's the condition of both male fittings where both connectors connects to, are they smooth to touch with no scratches whatsoever ? The fuel pump on those are heavy duty ones, the diaphragams are mylar made, a though plastic film, has nothing to do with rubber ones that balloons real fast with E fuels.

The fuel pump is mounted with two side screws on to a rectangular gasket, with a scredriver adjust both tight, if bit loose the fuel pump will not work as it should as air could be entering there and loosing vacuum. Prime bulb with arrow facing upward till firm, disconnect the carb's fuel entrance, put hose into a container, start the motor at idle/meutral and check if there's a strong fuel flow. Can do it while flushing on muffs. Check both to rule fuel system issues, which I doubt.

You need a good analog meter DVA capable or a digital one and a auxiliary DVA converter. Check this related thread : https://forums.iboats.com/threads/which-one-is-best.743294/

Will anticipate that sometimes both tests could end up in being useless if the electric component to check shows good under such tests, but with erratic electrical behaviours when heating up which are the most complex to troubleshoot fast. Better be a failing Ignition Coil which is cheap, the CDI on those costs a whopping + 250 bucks.

Happy Boating​

I'm going to start on the issues 2maro, going to look at fuel pump then coil, primer bulb doesn't stay hard but when running yesterday I kept squeezing bulb but no difference in the way it ran. Had some wetness around fuel fill hole and guage on portable gas tank

 

[Sea Rider]

The fuel bulb will only remain firm when correctly primed before the motor is started, provided that the float's needle closes firmly onto the fuel valve. Once the motor is running the bulb's built in pressure will cede and the fuel pump will start doing its sucking job....

Happy Boating​

 

[terry alvis]

The fuel bulb will only remain firm when correctly primed before the motor is started, provided that the float's needle closes firmly onto the fuel valve. Once the motor is running the bulb's built in pressure will cede and the fuel pump will start doing its sucking job....

Happy Boating​

thanks for all the help, i will check things out 2day, we have one more good day weather wise

 

[MattFL]

If you were squeezing the ball and the problem still happens then that would make a fuel delivery issue (fuel pump, air leak in the fuel line, ...) unlikely. Still check the fuel filters under the hood though.

 

[terry alvis]

sorry guys for being gone so long, iam moving to mississippi looking at houses, etc... but iam back on working on boat. going to change the CID UNIT, i know its bout $250 but iam tired of b.s. going to check fuel pump also also going to look at fuel tank strainer

 

[Sea Rider]

but iam back on working on boat, going to check fuel pump also also going to look at fuel tank strainer

The entrire fuel system tank to carb must be immaculate clean when troubleshooting fuel related issues...

Happy Boating​