2001 75hp yam 2stroke misfiring and bogging

[Tomtom121212]

Hi folks. New to the forum. I've recently bought a 75hp yamaha 2 stroke. I've done all the obvious things to try rectify my problem. It starts fine, it revs pretty high at first then once the revs settle, it'll splutter and then cut out. It'll start straight back up again however, but then do it again. If I manage to engage it into gear before it cuts out, it just bogs and dies. It's an intermittent problem as I have been out in the boat and it sometimes runs fine under load. But when coming alongside the pontoon it will cut out when I engage neutral to go astern. It will only rev up to 4500 when full throttle in gear, but will rev to 5500 in neutral. Is this normal? Or should it run higher than 4500 when full throttle? Tia

[brian3006]

. but will rev to 5500 in neutral. Is this normal?

WOW just WOW......

Please for your motors sake, don't do this...

4500 for WOT under load is on the low end of "normal" might need a lower pitch prop...

what rpm is the motor idling at? both in neutral and in gear?

might be time to take the carbs apart for a good cleaning..

[Tomtom121212]

Thanks for your reply. It's idling fluctuates. It can be anywhere between 12 & 7 I think the cdi unit might be faulty? So what should it ideally be maxing at when under load? The carbs have been off and cleaned.

[ausnoelm]

Just guessing, check spark on all cylinders, clean carbs again, but properly this time, check for air leaks, max RPM are way low, but get it running right first.

[Tomtom121212]

The spark is intermittent on the middle cylinder. This has been checked. Compression is good. What rpm should it be maxing out at under load? Could you tell me? Thanks

[brian3006]

The spark is intermittent on the middle cylinder. This has been checked. Compression is good. What rpm should it be maxing out at under load? Could you tell me? Thanks

Max under load is 5500 I believe.

[99yam40]

if #2 is not sparking properly, you need to find out what calls for that spark

[ausnoelm]

The spark is intermittent on the middle cylinder. This has been checked. Compression is good. What rpm should it be maxing out at under load? Could you tell me? Thanks

Fix this first before doing anything else, you want to see at least 5,500, but a bit more will be better.

[Tomtom121212]

Thanks guys. Does anyone know what a replacement cdi unit would cost? I'm struggling to find one

[99yam40]

I do not even see a listing for a 2001 75

where are you and this motor located

[99yam40]

if this is like the 90 it has 2 pulser coils to tell when to spark 1 & 3, but #2 is done by the CDI and CPS

Service manual for that motor helps when working on a motor

[Tomtom121212]

I do not even see a listing for a 2001 75

where are you and this motor located

I'm in Scotland.

[Todd H.]

Are you able to swap the ignition coil on #2 with one of the others to see if the problem moves.

[Tomtom121212]

I've done that. No difference