Has anyone ran the 4S SS impeller in a 2S

redrum · Post by **redrum** » 26 Mar 2017, 07:16

I have a new-to-me 95 Merc 45 Jet with the stock aluminum impeller. I sharpened up the impeller, which had been severely defiled

. It runs great but I wanted to get a stainless impeller for it. I didn't know the whole 4S cutback to the 2S impeller under the same part number. I ordered a new stainless impeller and I'm guessing it's the 4S style now. I don't want to run it if I may lose holeshot or over rev the engine with no added MPH. I'm very happy with the performance right now. I was thinking about returning the SS and just getting a new aluminum one from OBJ. I'll attach a picture of theimpeller if anyone can confirm that this is the 4S model, thanks.

LarryMc · Post by **LarryMc** » 26 Mar 2017, 12:34

I haven't run the 4S impeller in a 2S motor so I don't know how it would perform, but I can identify your impeller for you. It's the 4S impeller. Below is the 2S & 4S side by side. 2S on the right.

Don't know if you would be interested, but I have a Wooldridge 4 blade SS impeller for sale in the Classified section.

handyandy · Post by **handyandy** » 27 Mar 2017, 09:09

buy a cheap tachometer off ebay and try it if it revs to high sell it rotus on here might buy it I know he has a 4s and might want a SS impeller for it maybe. I'd be curious to know how it runs on a 2s

rotus623 · Post by **rotus623** » 27 Mar 2017, 10:17

Hah, thanks Andy, you are darn right, I'd consider it if the OP doesn't want it.

handyandy · Post by **handyandy** » 29 Mar 2017, 11:08

redrum wrote:I have a new-to-me 95 Merc 45 Jet with the stock aluminum impeller. I sharpened up the impeller, which had been severely defiled . It runs great but I wanted to get a stainless impeller for it. I didn't know the whole 4S cutback to the 2S impeller under the same part number. I ordered a new stainless impeller and I'm guessing it's the 4S style now. I don't want to run it if I may lose holeshot or over rev the engine with no added MPH. I'm very happy with the performance right now. I was thinking about returning the SS and just getting a new aluminum one from OBJ. I'll attach a picture of theimpeller if anyone can confirm that this is the 4S model, thanks.

Did you try running it yet?

redrum · Post by **redrum** » 02 Apr 2017, 08:20

handyandy wrote:Did you try running it yet?

No, not yet. I'm currently working on a Wetlander 3L kit.

Lil' Blue Rude · Post by **Lil' Blue Rude** » 02 Apr 2017, 13:35

The 4 stroke impeller will be fine in your 2 stroke. Might even be better considering you have the 52cube merc. I've got a friend with a 56cube omc and he's running a 4 stroke impeller and there's not much difference rpm wise maybe 200rpm nothing crazy that's going to over rev a stock motor. Plus the stainless will last way longer then the aluminum ever would.

redrum · Post by **redrum** » 15 Apr 2017, 13:28

The results are in:

Aluminum 3 blade Impeller - 29.7 MPH @ 5,400 RPM
Stainless 3 blade 4S Impeller - 30.0 MPH @ 5,300 RPM

Not the results I expected but now I know.

LarryMc · Post by **LarryMc** » 15 Apr 2017, 14:15

I'm surprised that you got higher RPM with the aluminum 2S impeller than the SS 4S. When I first got my Mercury 4S 40 Jet, I tried both the 2S SS and the 2S aluminum impellers. I got around 4900 top end RPM with both. With the SS 4S impeller, I get around 5200 RPM. Guess the 4S just doesn't have enough power to turn the 2S impeller any faster.

mphelle · Post by **mphelle** » 15 Apr 2017, 14:49

All good information, it would seem that redrum got one of the old style ss impellers.

LarryMc · Post by **LarryMc** » 15 Apr 2017, 17:34

mphelle wrote:All good information, it would seem that redrum got one of the old style ss impellers.

Don't think so, the photo that he posted shows a new 4S type impeller.

redrum · Post by **redrum** » 15 Apr 2017, 18:03

I think my aluminum impeller is original. It has been ground on for sure. Here they are side by side. I bought the SS one new just last month. Im pretty sure it's the 4S model.

Hoping rotus will buy the SS one from me and I'll get that 4 blade from Larry then post the results.

Gotta say I'm extremely happy with the upgrade from the 50/35. Just better overall performance and the 3 cylinder sounds good

mphelle · Post by **mphelle** » 15 Apr 2017, 18:52

redrum, if your new impeller is still out, could you post a photo of it laying on it's side with the same orientation that LarryMc used in his photo. Thanks

redrum · Post by **redrum** » 15 Apr 2017, 19:57

It's still in the pump now. It is in the first picture up top. Here are a few more pictures I have of it.

mphelle · Post by **mphelle** » 15 Apr 2017, 20:08

No problem, LarryMc shows impellers from two different suppliers and it's easy to see how much material has been removed from Merc's new casting.