Question Regarding First Impeller Change

[Joeprunc]

Ok...I decided to change my impeller yesterday because my boat was used and the seller could not remember when it was changed last. Sorry for the long post, but you can skip to the question at the bottom.

I went to West Marine and got a Jabsco Replacement Impeller for Mercruiser #47-59362. I've got a 350 Mag Ski GM motor and that should be the part number.

The old impeller didn't look too bad, probably could have lasted another season. But the old one had 8 flutes and the replacement (Jabsco) had 10 flutes. The height and size between the two are the same. So I decided that because they are the same size that it just must be the difference between a Merc Part and an aftermarket part.

The new impeller brass bushing was a bit hard to get on the shaft...the shaft is a 3/4" dia. and the replacement impeller is designed to fit a 3/4" dia shaft. I figured because the sleeve is brass (or copper) the initial tolerances are tight, but after use the sleeve will yield and not the steel shaft. So did a little filing on the ID of the sleeve and lubed it up, and with some elbow grease I finally got the impeller back on the shaft. Lubed the rest of the provided impeller grease inside the housing, and bolted everything up.

I kept the old impeller as a backup for now. I will start and run my engine in the driveway before the next time I take her out, making sure everything is tight and not leaking. She is winterized for now, till the next nice day we get.

Question: Does it usually take a bit of force to slide a new impeller onto the shaft? Should I be worried about having a 10 flute vs 8 flute impeller in my sea water pump, although the part #s jive?

Thanks

[dogbert]

Whatever you do, don't run that impeller without fake-a-lake in your driveway. I'd order a new impeller in the packaging as a backup. The impellers dry out, which is how they fail in the first place.

To answer your question, the impellers are supposed to be a tight fit.

[Joeprunc]

Yea I've got the fresh water flush plunger for starting the boat in the driveway...I just don't want to start it now because the block is drained and engine fogged.

That is good to hear that they should be a tight fit between the ID of the impeller sleeve and shaft, I was a bit hesitant installing it.

Has anyone else installed a 10 flute impeller vs an 8 flute?

[chpthril]

The snugness of the impeller hub to the drive shaft has me puzzled. The impeller shafts are somehow "keyed" in order drive the impeller i.e. Woodruff key, splined, flat spot, etc. The fact that you had to grind down then force the impeller on

http://www.jabsco.com/files/section_...ent_07.pdf.pdf

[G-MONEY]

Yea I've got the fresh water flush plunger for starting the boat in the driveway...I just don't want to start it now because the block is drained and engine fogged.

That is good to hear that they should be a tight fit between the ID of the impeller sleeve and shaft, I was a bit hesitant installing it.

Has anyone else installed a 10 flute impeller vs an 8 flute?

In all honesty you should have changed the impeller at the beginning of next season and not before you winterized. I don't want to sound rude, I just wanted to give you a suggestion on a better time to change it. Regardless on when you changed it's a good thing you changed a bad impeller can ruin a great day real fast.

[Joeprunc]

The snugness of the impeller hub to the drive shaft has me puzzled. The impeller shafts are somehow "keyed" in order drive the impeller i.e. Woodruff key, splined, flat spot, etc. The fact that you had to grind down then force the impeller on

http://www.jabsco.com/files/section_...ent_07.pdf.pdf

Thank you for that PDF...I installed the 17954-0001-P, which is the only one shown to be for the Mercruiser. Looking through the rest of the table I did not see an 8 blade impeller for a 3/4" diameter shaft nor was there anyother impeller that had a 2" width for a 3/4" dia or larger shaft.

As far as filing: I deburred the edges of the insert and took a triangle file to the corner of the flat spot to make it more pronounced. Just a little metal was removed.

I am guessing the tolerances are just a bit tight because brass is such a malleable metal...or maybe it slipped by the QC.

[Joeprunc]

In all honesty you should have changed the impeller at the beginning of next season and not before you winterized. I don't want to sound rude, I just wanted to give you a suggestion on a better time to change it. Regardless on when you changed it's a good thing you changed a bad impeller can ruin a great day real fast.

I am still planning on taking her out this year...I've winterized just in case we get a cold night. I was going to wait till March or so to put in the impeller like you suggested, but last time I was out I noticed that it was running a bit warmer than normal. It was probably just because I was in a no wake zone for a while, but because I had no clue when it was changed last I decided to play it safe...well hopefully it will be safe.

[G-MONEY]

I am still planning on taking her out this year...I've winterized just in case we get a cold night. I was going to wait till March or so to put in the impeller like you suggested, but last time I was out I noticed that it was running a bit warmer than normal. It was probably just because I was in a no wake zone for a while, but because I had no clue when it was changed last I decided to play it safe...well hopefully it will be safe.

never mind then