18hp nissan 2005 runs rough , lack of power

[Chuck_1443]

i,ve always unhooked the fuel line to let it run out of gas , ive not cleaned the carb thoroughly but have sprayed it out with choke cleaner . thanks

 

[TOHATSU GURU]

Re: 18hp nissan 2005 runs rough , lack of power

Great! On behalf of everyone here, we thank you.

 

[pvanv]

Re: 18hp nissan 2005 runs rough , lack of power

What do the plugs look like? Is there acceleration stumble? Does it run better after it's warmed up?

 

[Sea Rider]

Re: 18hp nissan 2005 runs rough , lack of power

Check gas pump diaphragms internal conditions for cracks or excesively balloned, tank and engine filters are inmaculate clean, try with a new fuel hose, sometimes works miracles on lack of power issues when all previous issues are found ok and all electrical parts are working properly.

Happy Boating

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

THe plugs are not new but very little use on them , a problem i have is I don't use this moter very much . This time last year I took it trout fishing and noticed that it wasn't pumping water very well (it would then it wouldn't , weak stream ) I took it home replaced the water pump , started to see if it was working and didn't take it out until last summer . It started fine but wouldn't get to full trottle ( stamble,studder then take off , then bogg back down ) again I didn't use this moter only a few times a year . The fuel line has quick connects and holds gas I wonder if it has buildup in it Like sea rider said? When I unhook to run it out of gas I unhook from the motor and not the tank. Thanks I appreciate the help

 

[Sea Rider]

Re: 18hp nissan 2005 runs rough , lack of power

The issue with fuel line is not the line itself but small connectors o'rings that wears with time letting air inside fuel line, a pitty that such o'rings are not sold separately as spare parts, check auto parts for them, replace both and test.

Happy Boating

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

The issue with fuel line is not the line itself but small connectors o'rings that wears with time letting air inside fuel line, a pitty that such o'rings are not sold separately as spare parts, check auto parts for them, replace both and test.

Happy Boating

replace the quick connects? or the whole thing line and ball. thanks again

 

[Sea Rider]

Re: 18hp nissan 2005 runs rough , lack of power

replace the quick connects? or the whole thing line and ball. thanks again

Before you do this change, must have your carb, fuel diaphragams and all electrical parts in opt working condition, if so, remove both extreme o'rings, go to a auto shop, buy same diameter for gas usage, one is slight larger than the other. Start by changing the engine connector o'ring as it's used the most, if doesn't get better, change tank connector o'ring too. Not good to remove both connectors as comes factory well pressed to avoid gas leaks while primming bulb hard. If using same connectors as placed on Tohatsu engines, doesn't have end balls, have plastic white pins.

Sometimes will experiment defective water peeing although water pump is in excellent condition, run a wire upwards with engine on, or compressed air with engine off, if still cloggs, sometime afterwards, spray a good dose of W-40 with red cannula up hole, let soak for some minutes, run cannula forward and backwards inside peing hole, it's same diameter, start engine, most of the time defective peeing issues are due to salt formations that clogs or narrows inside peeing passage.

Happy Boating

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

i replaced the plugs, put the motor in a 55gal drum , started it ,mud dobbers had stopped up the pee hole ,cleaned it out with a piece of wire its spraying really well i let it warm up, throttling up(in neutral) it has a hesitation then go's . i unhooked the gas line (thinking it would eliminate a air leak ? ) still the same stall throttling up . i noticed it surging while it was warming up , and the ball leaked a little gas while i was pumping ,it started first pull after it was warm though. what do you guys think ?

 

[pvanv]

Re: 18hp nissan 2005 runs rough , lack of power

If you have a leaky primer bulb/hose, it's easy enough to replace it with a new one. If short on cash, and the leak is only at the connector, see if you can match up new o-rings.

That stumbling and hesitation sounds like an overly-lean condition, so check all fuel system components, from the tank pickup, to the primer hose, connectors, fuel filter, pump, and carb. It may be indicative of needing a good carb cleaning. If the plugs are white, you are definitely too lean. If tan, you are probably OK.

 

[Sea Rider]

Re: 18hp nissan 2005 runs rough , lack of power

Have you tried that motor at sea, lake at wot ? Does still hesitates, bogs down and only want's to cruise at idle slow speed ? if so, that's air entering fuel line at some point assuming all electrical components are working properly. Are both male connectors at engine and tank completely polished without tiny scratches ? They must be completely smooth to touch to provide a perfect tight fit against o'rings for gas line to work properly.

Replace both oring's and test at sea, lake, with warm up engine as you can't wot on a barrel unless you have a special test prop, if married, your wife will kill you.. Other issue could be a lean condition as stated by Paul + low rpm for that model assuming complete gas circuit is opt clean condition. As you see there are a lot of tech variables at which an engine won't perform as expected. Good luck on your search, post end results for the audience.

Happy Boating

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

the motor is off due to my son and i are painting the boat to make it a duck hunting boat so it may be a week or so before i can test in water . with the hood off the hesitation sounds like an old 4 barrel carburetor . with the gas line unhooked from the motor(like running it out of gas) will it suck air through that port or does it seal off because it still has the hesitation unhooked? i'm asking to see if this would eliminate the line

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

thank you guys for hanging with me, i hope i'm not making you all too impatient

 

[Sea Rider]

Re: 18hp nissan 2005 runs rough , lack of power

When you remove engine connector the gas circuits shuts off because has another intenal small or'ring that seals against internal white pin, air entering fuel line is generally found at speeds other that idle, worst 3/4 to wot as will suck more air. The forum has given all of the troubleshooting for that engine, what's in the owners manual to look for and what's not, will be a wild guess giving an apropriate tech answer with grounded engine, test on water at different speeds and report back your findings.

Happy Boating

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

A question regarding the carb ( keihin bcm 3v9b te12) I've taken itappart to clean , on the bowl side beside the accelerator pump is a hole with a brass pin ? Jet ? Is it pressed in permanent or should it come out

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

A question regarding the carb ( keihin bcm 3v9b te12) I've taken itappart to clean , on the bowl side beside the accelerator pump is a hole with a brass pin ? Jet ? Is it pressed in permanent or should it come out

And checking spark , removing one plug wire at a time the motor would die . Is that normal ?

 

[pvanv]

Re: 18hp nissan 2005 runs rough , lack of power

A question regarding the carb ( keihin bcm 3v9b te12) I've taken itappart to clean , on the bowl side beside the accelerator pump is a hole with a brass pin ? Jet ? Is it pressed in permanent or should it come out

Sounds like the metering port for the ABS (auto by starter) electrically-operated enrichment system (similar operation to an automatic choke). It is fixed in place.

 

[pvanv]

Re: 18hp nissan 2005 runs rough , lack of power

And checking spark , removing one plug wire at a time the motor would die . Is that normal ?

Maybe. Depends on overall health of the motor, as well as RPM when doing that.

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

Sounds like the metering port for the ABS (auto by starter) electrically-operated enrichment system (similar operation to an automatic choke). It is fixed in place.

would you know where i could view a good diagram of that carb?

 

[Chuck_1443]

Re: 18hp nissan 2005 runs rough , lack of power

i dont have a tach but i would guess 2500rpm no indication that it wants to die until i remove a wire

Maybe. Depends on overall health of the motor, as well as RPM when doing that.