nissan 25 hp four stroke help

[freedom35]

has anyone had the following problem?

my 25hp will start (same as usual),it will idle all day long, but if i increase the throttle it gets interesting.

out of the water (neutral or in gear) it will rev up

in the water in neutral it will rev up

in the water in gear it will start to rev up for about 2 seconds and just dies, no sputter,no pop, just bang dead?

up to this point there has been no work done to this motor since new (except oil changes and winterizing) just 5 years of trouble free fun.

since this started i have:

replaced the fuel pump and filter
checked the exhaust passages for blockages (nothing)
and checked / cleaned the carbs (spotless)

are these known to jump their timing? or ecu going bad??

 

[pvanv]

Re: nissan 25 hp four stroke help

Assuming you have an NS25A. Do you run the carbs dry at the end of each and every day? Why did you change the fuel pump? Was it leaking? No, the timing doesn't typically jump. What method did you use to clean the carbs? Have you checked for any loose wiring or a shorting kill wire?

 

[freedom35]

Re: nissan 25 hp four stroke help

i will start with telling you every thing i have done so far was "suggested" to me by the dealer,and nothing has helped.

fuel pump, i was told the ethanol content in our gas causes premature failure.

tank, lines, fittings, have been replaced

carbs have never been run-dry, fuel stabilizer is added religiously to every tank of gas.

carbs have been disassembled/ soaked/ blown through as i would to any inline multi- carb engine
(they were clean to start with, i have cleaned hundreds of motorcycle carbs, out boards are new to me)

exhaust system/passages were checked because it was "suggested" that seaweed/sand could get jammed up behind the prop and act like a collapsed catalytic converter on a car chocking it off at high rpm.

now the dealer is suggesting i buy a new ECU, i don't care if i have to buy a new ECU but i don't like guessing and i am pretty sure that is what they are doing at the moment.



now as far as wiring goes, i have looked over the controls/engine, nothing is unplugged/ frayed/corroded looking.

i have checked what switches i could:

the emergency kill on the engine and controls both work, unplug them and the engine dies, plug them in and it will start up and idle.

control switches, it will not crank in gear, it has to be in neutral

oil pressure switch seems to be working properly. turn ignition on the light comes on, start the engine light goes off.

i was thinking about taking my ohm meter and to start checking the wire harness for "unseen corrosion/resistance" but am leery of inadvertently causing a secondary fault complicating finding the first one.

dan

 

[pvanv]

Re: nissan 25 hp four stroke help

Grab your trusty Factory service manual (available from any dealer, including me), and start troubleshooting. I would never swap an ecu willy-nilly. Yes, you may need an ecu. You will need a good analog meter to test it, using the Factory service mahual as a guide. Emphasis on analog.

Your "suggestor" dealer is an idiot. Those fuel pumps will run on 100% ethanol if needed. I have *never* seen seaweed get jammed in the exhaust housing.

If the carbs ever sit for a week or two with US pump gas in them, they WILL varnish. Period. With or without any "snake oil" added to the gas. Start with a complete disassembly (including jets and emulsion tubes, etc.), 4-hour soak in real carb dip, followed by a thorough blow-out with carb spray.