13 replies to this topic

[dzpmantis]

Took the Doo out for a little spin last night, and didnt really see the performance I was expecting.
Weather was a bit windy, and the lake was a bit choppy
with 4 adults only got up to about 25mph according to the speedo.
I out weigh the other 3 by at least 35-40lbs, and I only weigh 170.
at 4000rpm, we were only going about 15mph.

I am thinking that maybe the impeller may need replaced. I will be replacing the spark plugs first.

Advice is appreciated.. Thanks

[no1stumper]

What it sounds like is a impeller problem. Have you had any other problems other than this?

[dzpmantis]

So far, no other problems. Have only had the boat for a short time. I was planning on changing the spark plugs, fuel filter, ect this weekend. I will inspect the impeller. What will I be looking for as visual signs? Or is is better just to go ahead and replace it? I have looked at the factory manual and am sure I could handle it without problem.

Also, if I do replace it, what is the best pitch rate for my Doo?

I see a 14/22 , 15/20, and 16.5/23.5

Where is a good place to purchase these things from?

[dzpmantis]

Took it out again this weekend and was only able to get to just over 30mph @ 5500rpm with only 2 adults aboard. How do I find out what impeller to buy? Should I buy it from Mercury, or online (about $200 less).

[WAJetboating]

at 4000rpm, we were only going about 15mph. I am thinking that maybe the impeller may need replaced. I will be replacing the spark plugs first.

Before you spend the money on those expensive plugs....

Was the engine able to smoothly run up to ~6000 RPM's? If so, the engine (and the plugs) are likely just fine and you have a jetdrive problem. If this problem developed "suddenly" that's another clue that it's most likely in the jetdrive.

Inspect your jetdrive, front and rear, for foreign objects. Plastic bag, piece of rope, etc. Anything that doesn't belong can cause turbulence and/or cavitation which will give you exactly this sort of behavior.

If that's all good, remove the intake grate and use a feeler gauge to check impeller-to-wear-ring clearance. It should be less than 0.050 inches all around. 0.100 is the max as recommended by the Mercury service manual, and is when you should consider replacing the impeller (first) and/or wear ring (second). Also check that the impeller hasn't been dinged by something passing through the jetdrive; a badly dinged impeller blade can cause this sudden loss of performance.

Report back!

[WAJetboating]

How do I find out what impeller to buy? Should I buy it from Mercury, or online (about $200 less).

Unlike jetskis, there aren't a lot of aftermarket impeller options for the M2 jetdrive. I've heard rumors that there is one, but I've never actually seen it.

Are you saying you've found the OEM impeller for $200 below retail? Where?

[dzpmantis]

Yes, Ran smooth all the way up to about 5500rpm. I will be changing the fuel filter, but not the spark plugs.

I did inspect it before and after we went out, and saw no visible obstructions or problems. I will take the cover off and do as you suggested. I was under the impression that the wear ring can usually be replaced to help eliminate cavitation, if there is nothing wrong with the impeller. Upon further review of the M2 shop manual, it does state that 75% of the wear is usually in the impeller.



Solas makes a impeller for Jet boats. MC-CD-22/39
http://www.solas.com...a...23&SwType=1

And I was looking at the wrong impeller online that was $200 less. So far one I have found via phone by Solas is $365, which is about $100 less than local retail.

[WAJetboating]

Yes, Ran smooth all the way up to about 5500rpm. I will be changing the fuel filter, but not the spark plugs.

Replace BOTH primary fuel filters. There's an inline filter right where the fuel line runs to the engine, and the fuel/water separating filter on the other side of the engine (looks like a car's oil filter). There's a third filter in the vapor separator but replacing it is a bigger job and it's downstream of these two filters anyway.

Clean and regap the plugs while you're at it. This engine is picky about proper plug setup.

I did inspect it before and after we went out, and saw no visible obstructions or problems. I will take the cover off and do as you suggested. I was under the impression that the wear ring can usually be replaced to help eliminate cavitation, if there is nothing wrong with the impeller. Upon further review of the M2 shop manual, it does state that 75% of the wear is usually in the impeller.

The way to know for sure is to use the feeler gauge as I suggested. That way you KNOW what the clearance is. If there's no obvious damage to the impeller and wear ring, and the clearance is OK based on the feeler gauge, there's no point in spending money on new hardware.

Solas makes a impeller for Jet boats. MC-CD-22/39
http://www.solas.com...a...23&SwType=1

Interesting. I wonder what they feel is their advantage over the OEM design.

Report back!

[dzpmantis]

Interesting. I wonder what they feel is their advantage over the OEM design.

Report back!

I cant seem to find the specs on the OEM impeller, so I dont know if the pitch is any different or not. They do have the same one listed for several years, engines, and lengths/weights. I wonder if the OEM is different for each model.

It does seem a little odd that it is 22/39 when many traditional props for similar weight:power boats are around 19. Most of theirs for the pwc or boats with dual engines are 14/19.

Oh, and they said that there was a 3 week lead time to get them. (This was from only one distributor)

[dzpmantis]

Update:

Checked the impeller, max clearance .016" Impeller has a decent edge on it, similar to an good axe (in sharpness). No dings, chips, or scratches.

Had to order the fuel filters (and oil), and will change them next, drain the carbs, and the tank, and start with fresh (treated) gas.

Took it out again this weekend, and with me and my wife, top speed was just under 35mph according to speedo (felt correct).

Any other things that I could look for?

[wayne99]

All you need is a wear ring and your problems are solved.

Update:

Checked the impeller, max clearance .016" Impeller has a decent edge on it, similar to an good axe (in sharpness). No dings, chips, or scratches.

Had to order the fuel filters (and oil), and will change them next, drain the carbs, and the tank, and start with fresh (treated) gas.

Took it out again this weekend, and with me and my wife, top speed was just under 35mph according to speedo (felt correct).

Any other things that I could look for?

[dzpmantis]

The clearance between the wear ring and the impeller is only .016" at the largest gap. This is well within the specs of a new set. Changing the wear ring would not net a closer clearance.

[keviseeb]

The clearance between the wear ring and the impeller is only .016" at the largest gap. This is well within the specs of a new set. Changing the wear ring would not net a closer clearance.

Although Mercury calls it a "wear ring kit" it is actually the whole housing. The Mercury M2 jet drive does not have a replaceable liner like the Rotax engine and drive does. The Mercury housing is around $490, the impeller around $456 and a dealer would charge around 1 1/2 hours to change them. Compare that to around $190 to replace a Rotax wear ring including labor. Rarely do we have to replace a Rotax unit impeller because the wear ring usually takes all of the punishment. Good luck with it!

Kevin Seeber
Kingsland Marine

[dzpmantis]

Although Mercury calls it a "wear ring kit" it is actually the whole housing. The Mercury M2 jet drive does not have a replaceable liner like the Rotax engine and drive does. The Mercury housing is around $490, the impeller around $456 and a dealer would charge around 1 1/2 hours to change them. Compare that to around $190 to replace a Rotax wear ring including labor. Rarely do we have to replace a Rotax unit impeller because the wear ring usually takes all of the punishment. Good luck with it!

Kevin Seeber
Kingsland Marine

Is this something that I should consider, given the clearance is 0.016", and there are no visible cracks or dings?

Do you happen to know what the pitch is on the stock impeller? It could be that the previous owner replaced it with a non oem product. How would I tell the difference? Thanks - Zack