M2 Jet Drive is not a Rock Crusher :-(

[jsgraham]

M2 Jet Drive is not a Rock Crusher :-( UPDATED WITH PICS and Measurements

Hello All,
Found a very nice unmarked rock pile this weekend with my 2000 Islandia. Shut it down as soon depth finder alarmed at 4 feet, but apparently wasn't quick enough. :facepalm: "Clunk" and no start. Pulled her back to launch, spent a few hours digging out a few rocks that were wedged between the vanes of the impeller, and between the impeller and stator. Got it all cleaned out and rinsed out, went out for a shakedown cruise. all seemed well :thumbsup:, until we put the tube on and tried to drag the kids around.

Lot's of what I am assuming is cavitation, and a knocking sound from the back of boat with synchronized vibration at the shift lever. At least the shift lever can keep a beat.. about 1 thunk per second.

Idled back to shore quietly and called it a weekend. I am assuming that the impeller and stator are now due for a rebuild, but want to see if there is anything else to check while I have her apart.. Thanks for any information, I will attach a few pics of the areas I am concerned with.

Joel

 

[jasguild]

dont feel too bad, a few months ago I was going up the hillsborough river. I drove close to one of those channel marker. Apparently they had replaced the marker post but only cut the old one down to water level. SMH. At high tide it was below water line and I did not see it. It put a big hole and scratch on the bottom of my boat.

I still complain in my sleep about the $800 repair bill but more glad that the boat did not sink that day. In fact it hardly took on any water.

 

[jsgraham]

Thanks for the words of encouragement, glad to hear that you didn't take on any water! Gonna be up against the clock on this repair, have another attempt at a vacation in 3 weeks.

 

[Coastiejoe]

A bit challenging to tell, but the one fin looks bent to me.

The max fin to wear ring should be 10-thousands of an inch. The wear ring clearance is crucial to the performance of the ski due to the tunnel drive. If the blades of the impeller are not bent, you can clean it up pretty well.

Pull the pump, put the impeller on a flat surface. Measure the fins from the surface up to the fins as the same place on the fins. If it is bent, which it looks like to me, that is an issue..

 

[Dr Honda]

All I can say is to take it apart... and see what the damage looks like up close. But yes, the impeller and ring will need some love.

 

[jsgraham]

Alright Folks,
after a weekend of wrenching, here is where I am at. Wear ring will be getting a good dose of JB weld, and the impeller needs some attention. Took a to of measurements, and would like an opinion on how these measurements stack up.

All measurements are from table to reference point:
Blade 1 = Back of Blade = 13.9mm .561 Front of Blade = 107.99mm 4.233
Blade 2 = B.O.B = 13.9mm .558 F.O.B.= 107.84mm 4.239
Blade 3 = B.O.B.= 14.3mm .565 F.O.B.= 107.60mm 4.231
Blade 4 = B.O.B.= 13.9mm .551 F.O.B = 107.82mm 4.233

variance = .4mm .014in variance = .39mm .008in


Next up measured along blade edge, marked as close to inch intervals as I could. point 1 is leading edge of blade, point 9 is back edge of blade.

blade 1:1 to blade 4:5 = 53.48mm 2.082 bld2:1 to bld1:5 = 52.25mm 2.065 bld3:1 to bld2:5= 3.05mm 2.104 bld4:1 to bld3:5 = 52.44mm 2.080 Variance = 1.23mm .017inch

b1:2 to b4:6=56.60 2.243 b2:2 to b1:6=55.90 2.194 b3:2 to b2:6=56.03 2.203 b4:2 to b3:6= 55.40 2.192 variance = 1.32mm .017 in
b1:3 to b4:7=62.12 2.444 b2:3 to b1:7=61.85 2.431 b3:3 to b2:7=61.32 2.416 b4:3 to b3:7= 61.25 2.409 variance = 1.20mm .051 in
b1:4 to b4:8=70.20 2.745 b2:4 to b1:8=67.97 2.673 b3:4 to b2:8=68.89 2.719 b4:4 to b3:8= 66.65 2.618 variance = .87mm .035 in
b1:5 to b4:9=77.67 3.054 b2:5 to b1:9=76.10 2.999 b3:5 to b2:9=76.82 3.021 b4:5 to b3:9= 75.56 2.965 variance = 2.11mm .090 in

I would think that accuracy within 2mm or .09 inch is probably about all one could expect from your average prop shop, correct me if I am wrong.

Sorry for the long winded explanation, but I want to provide a much information as possible.

I will attach pics to try and illustrate things.

Thanks

JG

 

[jsgraham]

Hopefully Doc and Coastie can eyeball these and give their .02 :thumbsup:

 

[Coastiejoe]

I would agree that it is close enough. That said, above 5mm I think I would get it tuned. Here is why. The wear ring clearance can't be more than 10 mm, but it doesn't move and it has everything to do with "slippage". As in, the water slips past the impeller once the wear ring is worn to much and you lose performance.

With the impeller, if it is bent, it will technically push (which is what it should do) and pull. When it pulls, it creates a major performance issue and it is in theory in reverse. Granted, a small bend means on a small pull, no where near a reverse issue, just trying to make a point. Any bend will cause a loss of performance as at the point of the bend, you will get reduced thrust.

 

[RiverPro]

Good morning fellows! I haven't checked in-in forever; way too many things going on. I skimmed a few threads and came across this. As I run a river boat, thus pump a lot of gravel, I'll give my two cents.

File the impeller and stator gouges flat, JB weld and smooth the ring, straighten bent blades best ya can.

Before assy, lay the ring on a flat surface, insert and push imp to one side. If the distance is 0.20~0.35 or so, put 'er together.

 

[jsgraham]

After a month of fiddling, the Blue Doo is back on the water and running strong! Plenty of pull, and tops out at 39ish per GPS. Thanks to all for the advice and encouraging words. :thumbsup: