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Thread: 3-stage Gremlin

  1. #1
    Member boondockinak's Avatar
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    Default 3-stage Gremlin

    I'll try to get all the facts thus far up to date. Danny and Joe have been a huge help so far, but I still havn't narrowed it down yet. So here we go:

    04' Kodiak 3-stage behind a stock Kodiak 350, currently 250ish original hours. Current impeller setup is 19,19,24, and seemed to be a well rounded setup for my application. Prior to any damage, I was doing right around 3500ish rpm for 35mph, and 4200-4500 for 40-45 mph. This April, I had some rocks get past the grate that shouldn't have. Bang smack and fireworks later, 3-stage was torn apart on the side of the Knik (thank you Danny), rocks removed, and reassembled. Immediately she had a good shake to her at idle, and hole shot was smoked along with much higher rpms etc. I think I was running 4000-4500 to stay at 30-35 mph, and 5,000 to run 40mph. Hole shot was 4500-5000 and took a country mile. I believe that my outer clearance was somewhere around .050 or less at that point, with leading edges and trailing edges looking awful.

    A whole lot of money later, I have rebuilt impellers from Professional Marine (or whoever they send them to), along with new seals etc. Stators looked good, short of a few minor dings. Wear rings were acceptable. I re-assembled a couple of nights ago, very carefully... Here is a question for everyone, I've heard five million ways that different people determine the forward orientation of their impellers. I've also determined that there may be some people running them backwards. Looking at Kodiak's diagram and cutaway from their website, the base of the blades (where they attach to the hub?), which is the longest distance from the flat face of the hub, is the forward orientation. As far as i can tell, jet boaters refer to this as "short side", verses "long side". So the "long side" is facing forward, according to Kodiak. This matches how they were marked "leading edge" when I got them back from the rebuild. So for the sake of discussion, I'm going to assume that I have them facing the right way. Obviously the 24 is a no brainer, if you have it facing the wrong direction, you're going to chew up your stator in front of it. I have been asked if they re-piched the impellers during re-build, and I haven't the faintest idea.

    During rebuild, replaced all the o-ring seals, new cutless bearings and sleeves, and used plenty of grease. My new outside tolerance appears to be .016 to .017 when all of the slack is taken out, and I'm checking one side (pulling the shaft down per say, until the impeller hits the wear ring, and then measuring the opposite side). Again, stators looked good. Prior to assembly, shaft play at the back of the shaft couldn't have been more than 1/4" up and down, side to side etc. I was told by proffesional marine to use 105 ft. lbs on the back nut of the shaft. Using a couple of screwdriver handles in between the last impeller and forward stator (to keep the motor from turning), I achieved 105 on the nut. I'm told this seems a bit excessive on tightness, and am open to any opinions.

    Took it out last night for it's first run to Knik. Had a weird thing happen during fire up, it almost seemed like it took about 2-4 seconds, after the motor was running, for the pump to start pumping water (yes the boat was sitting in plenty of water). It's my understanding that depending on the angle of the ramp, as knik launch is steep, that people have had weird air pocket flukes, and the jet sucks air for a minute. Hoping that's what happened. Anyways, idle still has a pretty good shake..... I have no idea what's causing it. First hole shot after warm up (with approx 650 lbs of guys in the boat) was much better than before the rebuild, like worlds better. But still lacking from what it was before I feel like. With just me in the boat, it looks like about two boat lengths to get it on step.

    RPMs are not what they were before the damage. I'm looking at around 4,000-4,500 for 35mph, and 4,500-5,000 for 40mph+. Top end feels really spungy/squishy to me, without a lot of response.

    I've checked everything I know to check at this point and I'm out of ideas. Motor is having no issue getting to RPMS, so it must be a pump issue, and the shaking at idle has me worried...

    Thanks in advance.

    -Rob
    ~Alaska born and raised~ •'04 Duckworth, 5.7 w/ 3-stg. •High side Lowe, '13 Yami 25 prop+Merc 40/30 jet
    •Ranger 6x •CAT atv w/ 27" rubber •A very large moose buggy •M7 153" "Earned, NOT given"

  2. #2

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    There is a possibility that you have a bent shaft. Next I would take a close look at the u joints between the pump and the flywheel. Is it possible something broke when the rocks jammed it up. Check the bolts that have the flange bolted to the flywheel. The angle on the blades of impeller should be angled in the same as the 24. Where are you using the grease ? The reason that I ask is that grease can have a bad effect on rubber if it is not made for contact wit oil and grease. The big difference that you are seeing on the RPM sounds like that it is possible that your 2nd and 3rd stage impellers might be in backwards. Just guessing with out seeing the unit.

  3. #3
    Member boondockinak's Avatar
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    Figured out i definitely have a tach issue. Today I ran the boat and it seemed that the RPMs were right where they should be, about 4300 tops at around 40-45 mph. A friend with a lot of jet experience felt the vibration and feels like it's typical for a 3-stage. Now I'm down to my porpoising issue which has returned, and my ultra rich idle, dieseling issue. Pretty sure that re-straightening the back edge of the boat will fix the porpoising issue.

    Installed a fuel pressure regulator and gauge today, didn't help the idle. Any typical idling issues I should be aware of on these 1409 carbs? I'm getting little to no adjustment out of the idle screws, and fuel can be seen pouring in while its idling... Doesn't like anything below 1100 RPMs or so, sputters and spits and seems to flood out, sometimes dieseling really bad before it finally stops.
    ~Alaska born and raised~ •'04 Duckworth, 5.7 w/ 3-stg. •High side Lowe, '13 Yami 25 prop+Merc 40/30 jet
    •Ranger 6x •CAT atv w/ 27" rubber •A very large moose buggy •M7 153" "Earned, NOT given"

  4. #4

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    You could have a little vibration from your jet unit but it should not be something that stands out.You are dealing with a very precision piece of equipment and if your vibration is excessive it will shake its self apart with broken bolts and so forth.I have ran a 3 stage for over 30 years and if I have a shake like that I work on it right away.Remember that the jet unit is turning the same rpms as your motor.Another thing is you mention in your original post you mention plenty of grease .Where did you use the grease? The stator O ring should not be put together with grease as a petroleum product will cause rubber to swell and when you remove them the next time they may not go back very easy. Use vaselene as it will not cause this problem.

  5. #5

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    Vaseline= "petroleum Jelly"




    Quote Originally Posted by Big Bend View Post
    You could have a little vibration from your jet unit but it should not be something that stands out.You are dealing with a very precision piece of equipment and if your vibration is excessive it will shake its self apart with broken bolts and so forth.I have ran a 3 stage for over 30 years and if I have a shake like that I work on it right away.Remember that the jet unit is turning the same rpms as your motor.Another thing is you mention in your original post you mention plenty of grease .Where did you use the grease? The stator O ring should not be put together with grease as a petroleum product will cause rubber to swell and when you remove them the next time they may not go back very easy. Use vaselene as it will not cause this problem.

  6. #6

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    [QUOTE=boondockinak;

    Installed a fuel pressure regulator and gauge today, didn't help the idle. Any typical idling issues I should be aware of on these 1409 carbs? I'm getting little to no adjustment out of the idle screws, and fuel can be seen pouring in while its idling... Doesn't like anything below 1100 RPMs or so, sputters and spits and seems to flood out, sometimes dieseling really bad before it finally stops.[/QUOTE]

    Check the carb base gasket and ensure there's no leaks around base gasket Had a 350 TBI in recently that for some reason, sucked the base gasket in on the stb side. Not something you would suspect on an engine that has had years of trouble free running. You should be able to set the idle to 700-800 rpm with smooth idle. Hopefully you've fixed the tach issue and verified its accuracy with a timing light or similar device with an rpm function. If your idle can't be lowered you may need a carb rebuild.

  7. #7
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    I had dieseling on my 350 (same carb) when its idle was at around 1100 RPMS. Adjusted idle to 850 RPMs and the dieseling stopped. Seems unlikely that the carb would need to be rebuilt with limited use and as clean as your entire setup appeared. It is probably worth just double checking that nothing is restricting your carb from being fully closed. Sometimes we miss the obvious such as the throttle cable or a little catch in the movement of the carb that will not allow it from fully closing. Vibration in that jet unit sounds scary at between 3500 and 4500 rpms. I haven't noticed any excessive vibration in any of the boats with 3 stages I have been in so I would definitely keep looking into it.

  8. #8

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    The type of petroleum products that I was referring to being bad for a lot of rubber products was automotive grease and oils. Vaseline is the lube that keeps the Rainbow flag flying.



    Quote Originally Posted by Cresent Hills View Post
    Vaseline= "petroleum Jelly"

  9. #9
    Member Grayling Slayer's Avatar
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    Sounds like either the float bowls need to be adjusted or the needle seats are not sealing. Needle seats are a very common problem on any motor that sits in storage a lot.

    Sent from my Nexus 6 using Tapatalk
    "I'd rather be fishing!"

  10. #10
    Member boondockinak's Avatar
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    Thanks for the responses. I am 100% positive that the tach has an issue, as there is no way this motor runs at the "5500-6000" rpms that it routinely says that it is. I may not overhaul a buick every day, but I've been around enough sbc's my whole life to know the difference between 4300 rpms and 5500-6000. When the tach decides to work correctly, my R's are right where they should be. After fishing the boat at the Kenai for three, very long days this week, I am confident that the Jet is working like it should. With the exception of some trim issues with the boat, I had full power without any mushiness in the go pedal, and it hopped up on step with 4-guys in the boat and boat full of fish. It does not shake under full power/speed, only at idle etc.

    One thing worth noting, after having the boat hot, and shutting the engine down dozens of times etc, the fuel pressure regulator seems to have stopped the dieseling issue when I shut the motor down.... I'm not a carb head (obviously), but that doesn't make a lot of sense. Maybe it's just coincidence. I bought a carb rebuild kit, so we will check the gaskets, floats etc. After some research, I'm guessing a float mis-adjustment is the culprit. Looking at the documentation provided with the boat, it sounded like the original owner was having the same problems, and took it back to the dealer for repair. Receipt from the dealer says that "idle was adjusted".
    ~Alaska born and raised~ •'04 Duckworth, 5.7 w/ 3-stg. •High side Lowe, '13 Yami 25 prop+Merc 40/30 jet
    •Ranger 6x •CAT atv w/ 27" rubber •A very large moose buggy •M7 153" "Earned, NOT given"

  11. #11
    Member Jimw's Avatar
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    i take it you have flappers on your exhaust and you are not sucking in water through the exhaust when the motor dieseled. Yes there is a story behind that comment and yes i learned the hard way about dieseling and an inboard jet. Glad to hear you are up and running!!!
    2005 20' Weldcraft Sabre XL 350 MP
    SD309 AT
    2009 Polaris Dragon 800 163
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  12. #12
    Member boondockinak's Avatar
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    I do not have flappers, I suppose I've just gotten lucky that it hasn't sucked water... I've heard horror stories about it, I should count myself lucky I guess. Did this happen to your weldcraft? How bad?

    -Rob
    ~Alaska born and raised~ •'04 Duckworth, 5.7 w/ 3-stg. •High side Lowe, '13 Yami 25 prop+Merc 40/30 jet
    •Ranger 6x •CAT atv w/ 27" rubber •A very large moose buggy •M7 153" "Earned, NOT given"

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