92 Yam 175 runs terrible when try to go over 2000 rpms.

[Telstar_2112]

Our Grady has a 92 Yam 175 that runs and idles great up to around 2000 rpm then starts missing and kicking something terrible, like it will jump off the back of the boat! Previous to this weekend it ran fine all summer.

We tried all fuel related things like new diaphragm pumps, filters, and even running from a completely separate fuel can and also changed the spark plugs. No help- same thing. We suspect something with the CDI ignition but are told that is pretty rare to go bad. Anyone have any ideas as to what we should check next?

TIA, Telstar.

 

[23foot]

Re: 92 Yam 175 runs terrible when try to go over 2000 rpms.

I had the same type of problem you're having. Tried the same things you tried. I was recommended to clean and rebuild the carbs. I took them off this week and they are full of crud. Half my low speed jets were plugged with sediment. I was running a 20 micron filter, which obviously didn't filter everything. Yamaha recommends a 10. I'm going to put them back on this weekend. I'm confident it will fix the problem so try cleaning your carbs. Hope it helps

 

[Telstar_2112]

Re: 92 Yam 175 runs terrible when try to go over 2000 rpms.

We can try that but for some reason I have my doubts. It came on suddenly and runs terrible once we hit that rpm, kicking and popping and surging etc. I would think if the carbs got clogged it is unlikely that all three carbs, high speed ports only, cloggged at once. Maybe just one being screwed up can make it run like that but I am not sure?? We suspect somthing electrical like the CDI but at $700 need to make sure first so maybe your sugestion is worth a shot.

Anyone know how critical it is to use the special meter mentioned in the Yamaha manual to measure the resistances in the CDI unit? We have a regular, high quality, Fluke digital multimeter.

Also, one manual we have says it is even better to measure the voltages at some of the various wires comming from the cdi while running or cranking the motor. The wires are pretty well contained in the plugs. Anyone know how you are supposed to measure the voltage? I am reluctant to pierce the insulation anywhere due to the saltaire environment.

TIA,
Telstar

 

[Telstar_2112]

Re: 92 Yam 175 runs terrible when try to go over 2000 rpms.

My partner in the boat fixed it!! With info from these boards we decided to confirm that the alarm buzzer was indeed working and he found a loose/corroded wire at the alarm up in the console at the helm! Boat runs great now, so I guess the rev limiter alarm function had been kicking in. I am surprised at the way the engine reacted, popping and kicking so much etc. We don't remember that during other times such as low oil alarm.

Also in taking it for a ride there does not seem to be any alarm condition so it must be a kind of "fail-safe" circuit, which is good to know.

Thanks,
Telstar.