Yamaha 1991 250 pulse coil bad

[FHARVELL]

I have a Yamaha 250TURP (1991) on a 23' 1975 SEARAY, the engine RPM drops to 4200 after getting on plain from 5300 when full throttling from idle (and it gets on plain FAST when doing this), of coarse causing the boat to slow, if I ease into it (from idle), it eventually hits 4200, but no higher, this approach does not get me up on plain QUICKLY either, If I idle a few minutes (and it has to be at least 5-10) then full throttle - it performs exactly the same as first mentioned (gets on plain fast hits 42 mph, then drops back to 29 mph)- the motor has performed like this for some time, EVERY time, other than that the motor performs perfect, I'm told the high speed stator trigger is failing or the high speed stator is failing caused by the rise in heat produced when running at higher RPMs - all I see in the parts diagram is the pulse coil - Am I heading down the right track or could it only be in the control box? could a bad stator or timing base be the cause? I was told the Black box was replaced in the past and That's IT. I don't know if it was doing this before that though.

 

[WillyBWright]

Re: Yamaha 1991 250 pulse coil bad

I'm working on an 89 200 that had a broken lead from one of the triggers. The trigger coils are very reliable. The failure usually occurs when one of the wires from it breaks internally at the point where it exits the assembly. Moving the throttle flexes the wires at that point and one or more can break inside the insulation. There are 3 pairs of wires to the assembly. You can see them below the flywheel, they are white with different colored tracers. Check the pairs with an ohmmeter. If you come accross one pair with no continuity, you'll probably find the guilty wire.

 

[rodbolt]

Re: Yamaha 1991 250 pulse coil bad

your 250 is so incredibly different from a 200 its no comparison. go through the carbs and the fuel pumps. also a bad T-stat can cause a #6 carb lean out. its all testable but ya cant shotgun it. a CD-77 multimeter or equavalent is mandatory. the diagnostic test lamp can be very helpful. if you wish to play you gotta pay. no other way around it.<br />but there were some stator issues in those years. in fact some were done under warrenty. but yours is older than the records yamaha keeps so there is no way of knowing.

 

[FHARVELL]

Re: Yamaha 1991 250 pulse coil bad

I noticed that about the 200, I've already completely worked over the carbs and cleaned the jets and bowls. When I say the motor drops back, this is not a gradual thing, it happens pretty instantaneously, as if the throttle was being jerked back, which has me pretty convinced this is an ignition problem. This is definitly not an intermitting problem either. There just doesn't seem to be many components there that could be causing this except the Expensive ones. I'd like to at least be able to narrow this down before I start buying parts or surrender it to the shop. I'm not an outboard motor tech, but I've never had to take anything I've owned to a mechanic except to ask advice. (which I've received several contradicting versions regarding this issue- some of which I know just doesn't fit). I'm with you on the fluke and test lamp, and yes I'm aware that the triggers on older yamaha's were a big problem. Does my model even have trigger coils cause I don't see anything in the scats except the pulse coil and ignition coils. Please feel free to review my initial symptoms because accuratly describing them seems to be my biggest problem.