90 H.P.slow to pickup speed

I have a 1984 yamaha 90 hp outboard, it starts and runs fine with one exception, you can give it throttle while idling and it takes a while to get up to speed, it idles fine, runs out fine at top speeds but it is the in-between throttling up that I am having problems with, it acts to me like a car with a bad spark advance. Does this engine have something like a spark advance and if so where is it located and is it ajustable? Any help would be greatly appreciated...Thanks...Ken

[boats.net]

The 1984 does have a mechanical timing advance. Check lingage for smooth operation.

90 HP slow to pickup speed

Thanks for the reply, I'll give it a try. I just purchased this boat and tried it out the first time and discovered this problem, but someone also told me it could be the wrong size prop, I think it is a 19 pitch on it now, does that sound right to you and if not what size prop should I be running? Oh yes the boat is a 1986 Procraft 1650 Bass Boat. Thanks....Ken

any ideas on prop size???

[boats.net]

You need to prop it so it runs wide open between 4500 and 5500 rpm's. If it's running too low in rpm's then drop to a smaller pitch prop, too high go larger pitch.