'92 25 h.p. Nissan cuts out at high rpm's

[clk219th]

Hi all! I've got a '92 NS25C2 2 strk. that cranks right up and idles great. After about half throttle, it starts to cut out. It doesn't bog down, just a hard miss. Carburetor has been cleaned pretty well as far as I know, and it's running on fresh gas/oil. I've got the Clymer manual to start checking things out, but I thought it was worth a shot to get some expert tips on where to start or obvious things that I may not know. Any help would be greatly appreciated. Thanks in advance.

Also wondering if the 25 to 30 hp conversion by removing or changing the carburetor gasket works on this year model.

 

[lots of boats]

Re: '92 25 h.p. Nissan cuts out at high rpm's

Hi
Have a look to see whether there is any sign of a high tension lead problem, cracked old leads, black in coil boots if these pull off or can get loose, wire pulled out of the clip the plug jams into, and listen for a spark snap. Crank it in the dark with the plugs out and keep stretching the spark jump to see whether the spark leaks off someplace when you ask it to make a large jump to ground. Cheers.

 

[TOHATSU GURU]

Re: '92 25 h.p. Nissan cuts out at high rpm's

A high speed miss can be a fuel system, ignition system or mechanical system problem. You have to pick one and then work your way through the possibilites. As the fuel system is the source of most problems with outboards I would start there....But do a compression check, check for fire and check your gear oil first.

 

[chevyjet]

Re: '92 25 h.p. Nissan cuts out at high rpm's

Oh ya gear oil will cause a miss! NOT!!! not unless you put it in the SPARK plug, hahahah.

Try pumping the bulb when its missing to rule out a bad fuel pump.

 

[TOHATSU GURU]

Re: '92 25 h.p. Nissan cuts out at high rpm's

The difference between an amateur and a professional can sometimes be judged by how they approach a problem. As a professional I usually advise people to consider the engine as one system and then divide it further down into sub-systems that interact with each other in certain ways. People with little or no experience in outboard mechanics often fail to consider how one system can interfere with another system in a totally non obvious way. I have seen way too many lower units with binding bearings seize at high speed and have clutch dogs slip causing people to describe the problem(s) as a miss, momentary bogging and my personal favorite, hitting a fish. The 30 seconds spent checking the gear oil would give an immediate heads up to a problem there that might avoid hours of testing on the other engine systems.
Learn how things work on an outboard before opening thy mouth.

 

[lots of boats]

Re: '92 25 h.p. Nissan cuts out at high rpm's

Well chevyjet, thou kind of put thyself up on thee sandbar.

Am I beginning to wonder whether this forum seems rather empty of participants for reasons beyond product market share?

 

[clk219th]

Re: '92 25 h.p. Nissan cuts out at high rpm's

All thee's and thy's aside, I appreciate all the feedback. I'll be checking everything tomorrow, I guess starting with the fuel system. Great suggestions so far. I'll report back on anything I find. Thanks again.