1989 Force 85 hp impeller question

I need a new impeller for my 89 force 85 hp. I bought one from a dealer and it was the wrong part number. it was to large, to wide and the inside was also to large. then I bought one from Sierra which they said was the correct one and it was to small in the center. everywhere else was fine. my friend tried to put it on and when he pushed it it hit a lip it cracked. has anyone else found this to be a problem and if so how was it solved.
thanks Mark

Re: 1989 Force 85 hp impeller question

What is the model number of your engine?
Its a conventional outboard correct, not an L-drive?
What are the part numbers of the impellers you have tried?


The Mercury part number is 47-803631T

The Sierra part number should be 18-3030

Re: 1989 Force 85 hp impeller question

Roscoe I must have a freak of nature. the part number from Mercury ending in 631t is the impeller it calls for but it is to large. the Sierra 18-3030 looks like the one I had BUT would not fit over the shaft. my friend sanded the inside to make it larger but as he pushed it to go over a little lip it cracked. he has purched a quicksilver part ending in 630t which fits a 1988 motor and he said this on looks like mine. sounds to me as if they used 1988 parts in a 1989.
Mark

Re: 1989 Force 85 hp impeller question

You do realize that the impeller is larger than the pump housing. You need to bend the vanes to get it in. What I do is to install it on the shaft making sure I don't displace the key, lubricate it with Dawn --not oil (oil can deteriorate the rubber), then lower the pump housing onto it while turning the drive shaft in the correct direction.

For your information: The reason the impeller is slightly larger: The impeller sits slightly off center in the case so the fins bend more on one side. because of this, the volume between the fins is less there than on the other side. Any water picked up on the other side is pumped out here. At low speeds, the water pump is a positive displacement pump. At high speeds, water pressure forces the fins away from the housig wall, and the pump acts like a centrifugal pump.