Took my dad's jet sled with a 90/60 Mercury jet out last Sunday and managed to suck up some rocks into the intake. The grates are all bent, so it allowed some golf ball sized rocks to get in. One of the rocks lodged in the impeller area, which prevented the motor from turning over, so I took the grate off the bottom and put a crescent wrench on the main nut and turned it until the rock popped loose. After getting all the rocks out of the motor, I noticed it's only got about half the "get up and go" it had before. The impeller blades are noticebly dull and dinged up. Not sure what they looked like before the rocks were sucked up. The housing around the impeller(s) is/are noticeably grooved.

I'm thinking I should take the impeller(s) off and file the edges and put them back on. Are the impeller edges most likely the problem, or is there something else I should be concerned with? Thanks for any help!

Straighten the grates and file the edges from the inside of the blades and not the outside. Careful to not overfile too.

Or get a new 4-blade stainless steel impeller and new liner and you should be golden.

Yep, the liner might need to be replaced too if it's really beat up. Also, you can adjust the spacing between the impeller and the liner by moving the spacer washers up or down. You can check the outboardjets site for guidelines.

Been there done that. What cobble said.Good luck,


SZ

1. Take the lower housing off.

2. find something to use, with a hammer, to drive the "pin" out that holds the grates in. I used a big nail, that I ground the point down.

3. Straighten the grates.....I've done the filing bit, that Cobble Crusier mentioned.

4. If liner, has lot's of "grooves"......get new one.

5. Make sure you count the number of spacers, if you take impeller off, write the number down......so many on top, so many on bottom.

6. If the edge of the impeller is chipped and looks like it would be filed, do so.....I found this for you....

http://www.outboardjets.com/pdfs/IMPELLERSHARPENING.pdf

http://www.outboardrepairs.com/topics/005416.html

7. If any big chips.......buy new......Stainless steel is the way to go....many new motors now have the stainless steel impeller, right from the factory. Choice is either a 3 or 4 blade, impeller, in general a 4 blade....more get up and go but less top end.

Good luck........I have a feeler guage that is 8 -10" long, that makes it easy to check spacing of impeller to liner. Too much space, poor performance......... to little, engine might not start at all, to tight or if could wear a groove in the liner....right away.

Liners are $40+ ...... impellers ...... spendie!!!!!!!

Thank you, DrifterWA. Lots of good information. I'll be working on this this weekend and I'll post a report of how everything turned out.
Thanks again!!

#8 Tell Dad sorry

LOL

Dad was there when I sucked up the rocks.... he helped remove the foot and pull rocks out....

We're learning together....

Also, if you are really unlucky, the shaft and seals could be hosed too. If, after you fix the impeller, lining, and grate vanes the motor still has lost some giddiup, you might notice a strong vibration. If that happens, big bucks may be required. Good luck!

I personally wouldn't put a SS impeller on a 90/65... especially if it's a 4 stroke. You can google search the reasons why.

Take the impeller to Three Rivers and have them sharpen it for you. Get a new liner while you're there too. Shim it correctly and you should be good to go.

Sucked many rocks over the years... But when you describe "half" power, does the boat still get up on plane?

I once hit hard, sucking rocks and after cleaning it out I had about "quarter-half" power. Took it in to find I had screwed the computer up, about a $600 fix...

I've had my shaft shear off, but that just randomly happened when out fishing one day, that's about $800. Just chalked that one up to wear and tear over the years...

I can't imagine you fried your liner or dinged your impeller up too much from a few rocks... Although the grates are there for a reason, some bent grates aren't going to diminish power much. I ran mine for years with warped grates....

Does it appear to have about a credit card width space between the liner and impeller? If not, shim the impeller to where you have that proper gap.... Big problem with those smaller motors if that gap is much larger you lose proper suction... Personally, I think this sounds like your problem. The bigger motors are more forgiving, you don't notice that lack of power as much.... When you get down to two shims left on the bottom of the impeller, that's when I'd suggest a new liner...

Sharpening the impeller is easy, many step-by-step instruction guides on the internet...

Keith

You might have a couple of small rocks caught between the exhaust liner and the wall. Look at the back of the pump outlet. If you can see any small rocks caught between the exhaust liner and the outer housing, you've probably found about 90% of your problem. You can usually work them out with a pair of needlenose pliers.

I was reading this thread on break today and thought I would ask Glen Wooldridge. Here are his thoughts.........

alanmikkelsen- You are correct about rocks between the exhaust tube and housing.

The 4-blade works great with the 90/65. It doesn't lose any top end speed even with less RPM's which are sometimes confused with less speed. The 4-blade stainless is also better at getting a load up on plane. It stands up much better to rocks and wear.

As alreay stated, shim to .015 with a new liner if yours is badly groved.

Glen

Good to know Danny... thanks!

I think I see a SS impeller in my future on my 90/65.

Glen's pretty soft spoken till you get him talking about jet boats.

1. New liner
2. New impeller
3. Beg forgiveness.

Liner? I thought it was called a wear sleeve?

Anyhow, it might very well be a case of "death by a thousand cuts." All of the aforementioned issues do affect performance (grooved/worn wear sleeve, dull/damaged impeller, bent intake grates), to what extent depends on the nature and significance of the damage. You might also have a look at the bottom of your hull, especially if you have a tunnel hull as dents and deformation can affect performance as well. I'd be willing to bet a new wear sleeve and straightened intake grate fins will sort you out.

The glacial silt in a lot of the rivers in AK does a number on both aluminum impellers and wear sleeves. If you put more than about 100 hours on your jet boat in silty rivers, you can expect aluminum impellers and wear sleeves to last about two seasons before performance very notably starts dropping off.

"liner" is Outboard Jets, San Leandro, CA nomenclature.

Aha.

What do those guys know anyhow.

Half power might be inaccurate, probably has 80% of it's "pre-rock sucking incident" power. It gets up on plane, but doesn't have the high end speed. Like 15 mph instead of 25 mph....