Originally Posted by floater
i had a same problem a couple of years ago with a 30hp yam 3 cyl 2 stroke
turned out to be crap in one of the carbs there was a piece of material bloking the throttle needle i think thats what you call it this was cleaned and it sorted it out but as you say ran fine in the tank as soon as under load no power
the way the chap who fixed mine found it was to run the engine with air intake off and squirted in some "quick start" in to the carbs to identifiy which one was faulty
Sounds like a similar problem I'm currently having with with my 3 cyl Mariner('91, 50hp), took it out yesterday and had full rev range for about the first 10 mins then suddenly wouldn't rev past about 3000rpm ish(no rev counter so an educated guess
) Full power did return briefly in a quick burst a couple of times but then went all together
Spoke to Nos yesterday and he said either a duff plug or crap in one of the carbs. I changed all three plugs while out on the water with no improvement so guess it might be a carb problem.
When they discovered the problem with your 30hp Yam I assume they had to remove the carbs to clean them, what sort of timescale did that take? If you remove the carbs for cleaning, do you need to re-balance them before re-fitting? Do you mind saying how much they charged to resolve the problem?