30HP Yammie bogging down

[DaveHuz]

1985/86 30HP 3 CYL 2 STROKE OIL INJECTED.
Had a problem today coming off the bay with the engine bogging down and not coming up to full power after running all day. Thought I had run out of fuel but changed to the new tank and found out there was about a gallon of fresh fuel left in the old tank. MY initial thought was a clogged filter or water in the fuel but didn't seem obvious when I ran the engine a while on the fresh tank. My other thought was slippage in the linkage but that doesn't sound very probable. I think the problem might be related to the CD units (3 each) or the black box. Anyone know how to trouble shoot those problems or should I haul it directly to a Yammie mechnaic?

[DaveHuz]

Any one out there that has some insight into this problem? Everyone out fishing?- can't blame you.
Just checked the fuel filter- clean, checked the linkage- everything OK, oil level OK- did pull the plugs and noticed that one of the wires might have been a little loose and the top cap to the plug was not tightened down firmly. Could that have been the reason for the loss of power? Maybe not getting full spark to the plug at high speed? I did not notice any engine missing or misfires when I experienced the problem. Everything else seems OK and this engine has not had a lot of use given its age of 10 years. Gotta "road test" it to see if I experience the same problem after the adjustment on the plug wire.

[kloweree]

last time my Yamaha "bogged" down it turned out to be an ethynol problem and water in the fuel...I changed both filters even though I couldn't visualize any water in the filters......the boat ran fine for about a week and then the same problems again......had the carbureator re-built and problem was gone. I would start with the fuel.
If you choke it does it run better, then bog down again???...If its doing that its the carbureator. .

[DaveHuz]

Thanks guys, Gotta get it back out on the water again and test run it but I'm hoping it's related to the loose spark plug wire that I found. Water cooling seems good and it ran real well at low throttle getting me back in- no missing so I have a difficult time thinking it's the carburetion and fuel problem. Had fresh fuel in it and it has been running on 10% ethanol (that's all we can get here in MD) Had done a compression check a while back and all cylinders were within a few PSI of each other. Will let you know after I get it out again.

[DaveHuz]

Been a couple of weeks since I experienced the problem but it seemed to clear itself up after a short run out on the river. Ran out at full throttle and still bogged down but then seemed to clear itself up. Regained RPM and top end and has been running OK since then. Still trying to determine whether this was a fuel related problem that cleared itself or am I having problems with the CDI units or the black box. Anyone else have a similar problem and resolved the issue with some component replacements?

[sickcat]

Not that this will fix your issue but is could not hurt. Try running some Seafoam through it.

[reckless]

you keep saying cdi units i think what u are refering to are spark plugs, the black box that you are refering to is the cdi

[REZ]

my 2cyl 30hp yammy had similar issues, one was water in the fuel"ethanol" and the other was the fuel quik connect was sucking in more air than gas both at the tank and on the motor.

[Bamaskeetshooter]

I had your exact problem. It turned out that the previous owner glued the carb bowl drain screws. I used the motor for ten years without any problems. Took the boat to N.J. for some duck hunting and the ethanol fuel desolved the glue and clogged the carb.

The Yamaha 30 hp is a great motor.

[DaveHuz]

Thanks for the input guys. Have not experienced the problem again. Must have been a fuel feed problem. Regarding the CDI, I have one attached to each cylinder and the large black box on the starboard side of the engine. All's good now.

DaveHuz