late 70's 9.9 issues

[shootindave]

Working on getting by buddies tiller up and going for this duck season. At the end of last season it started acting up as follows:

The motor pull starts easy but doesnt seem to want to stay running in forward. You can put it in reverse and run around as long as its gassed, but forward kills it right off.

Today we tried some seafoam to see if we could blow out some carbon and get her goin. I noticed a small bit of rubber in the exhaust outlet where the water comes out. A search of this shows that it might be the "flapper".

This motor has been a GREAT winter duck motor in the past and very reliable so its worth getting back on its feet.

Any advise is welcome.

 

[OptsyEagle]

Re: late 70's 9.9 issues

I would suggest doing a compression and spark test just to see how strong the motor is. The forward only dieing thing is kind of wierd. When it is not running, can you put it in forward gear and turn it over so that the prop spins? As for the rubber material in the water outlet, I don't know what a flapper is but most likely the rubber is from your motor mounts breaking down and ending up in that cavity. Not the source of your current problem.

If you have good spark and compression, then it must be fuel. It never hurts to clean the carb once in a while. Since it seems to run well in neutral and reverse, I would assume that your fuel pump and tank are fine.

If you give us a model number, found on the transom bracket, we can tell you exactly what model year you have. It is useful, especially if you need to order any parts.

 

[the machinist]

Re: late 70's 9.9 issues

Has this motor been used as a fishing motor? If so you may have sizable amount of monofilament fishing wrapped around the propshaft in front of the prop. Since it was wound on in forward, it can become tight, but in neutral there is no power to the shaft & in reverse the rotation of the shaft is different, which could possibly allow it to not bind up then.

I have not seen this before, (but never tried the reverse) but on one of mine that did kill the motor in forward (1980 50hp) it was so dramatic that I could not even keep the motor running when shifting into forward.