70's 9.8 impeller

[hondatech]

I recently bought a couple of mercury 9.8's. I put the two together and made one good running one. The fellow gave me an impeller that he thought went to the motor. Im pretty sure the lower section is off a 71 model. I pulled the lower unit and removed the worn out impeller. The new one slides down the shaft to very near the bottom where the shaft seems to get just a tad larger in diameter. There it wants to stop. I checked the old one and it will slide onto the larger area with a little effort. The two impellers look to be the same as far as the blade diameter but when measuring the bushing in the center, there is a few .000's difference in the two, being the old one is the larger. I guess what I need to know is do I try to knock the new one down the shaft or do I have the wrong impeller? Is there another impeller that is suppose to fit this unit? If so what do I ask the partman for? Thanks, Chris

 

[dajohnson53]

Re: 70's 9.8 impeller

Hopefully someone else will advise you with the actual info you need. But, the only thing I can think of is to determine the serial number of both engines, then you can find corresponding parts diagrams and p/n lists on various websites or in your local merc dealer's database.

If the serial number is not on the transom clamp bracket, it should be on the powerhead, probably on the starboard side. If you're interested in the year of each, there is year number index on oldmercs.com

If all you need to do is look up parts, there are exploded views and parts lists by serial number on mercruiserparts.com - use the search by pictures option.

 

[DHPMARINE]

Re: 70's 9.8 impeller

Your partsman will probably ask you if the drive shaft measures .456 or .438. There are two different impellers.

DHP

 

[emckelvy]

Re: 70's 9.8 impeller

Certain newer models take an impeller with a smaller I.D. (.438"). Earlier models have a larger diameter impeller (.456"). Since you're mixing-and-matching you likely got the impeller with the smaller I.D. and of course it won't fit on the larger I.D. shaft.

The only other possibility would be if there's rust buildup on the driveshaft and in your case probably not so, since you have a measurable diff between the old impeller's I.D. and the replacement.

Part #'s for these impellers are as follows:

.438": OEM, 47-89980; Sierra aftermarket: 18-3054

.456": OEM, 47-89981; Sierra aftermarket: 18-3039

HTH............ed

 

[hondatech]

Re: 70's 9.8 impeller

You guys ar awsome! Thanks, Chris