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Thread: jet boat shim check - who?

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    Member Bullelkklr's Avatar
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    Default jet boat shim check - who?

    Who in anchorage can check the shims on a jet outboard? My uncle has a 50hp effinrude with a jet lower that he wants to take to someone to check it out. It is pretty new - like 120 hours, but when we had issues with the motor (fuel line leak, fowled plugs) last year on a moose hunt we changed out the impeller hoping for a quick fix - - and we had never touched one before and are not at all knowledgeable with them...

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    Really easy, there should be less than an 1/8" gap between the impeller and the sleeve. They say a match book is about the right gap. Pull the 6 nuts or bolts that hold your foot on. Pull the nut, and then its like Jenga, you take a shim from the bottom and you put it on top, Test fit the foot. If its too close it will rub. It may take a couple tries to get it right. Tighten the nut when you are done and put the foot back on.

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    Yes as slayer said, learn how to do this.....as least on your next hunt you will be prepared, note the tools you use to do this and make sure you have them in your tool kit. Learn how to sharpen the impeller also........Personally I think 1/8 is too much and would go for less than 1/16 and you just want to make sure it dont rub.......

    Maybe ask the shop to show you how to do if uncertain..... But, I have found watching is not the same as doing...........must not be true for some otherwise I wouldnt here so much about porn...haha....!
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    Yes you are correct, I find the 1/8 inch what I go by to decide if it's worth re shimming it, the correct gap is 1/32 according to their website. I need to re shim this weekend.


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    Member ptarmigan's Avatar
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    I just took my 50hp apart recently. I looked for some info on sharpening impellers here with little success. I just went for it and got it right. Found out there really is nothing to either the sharpening or shimming and it was noticeably better the first time out. Would be happy to swing by and show you what your looking for if your uncle isn't sure about it, just let me know.

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    If you want someone to show you, take it to Jay Kimberly on Arctic. Right by our shop. He is a great teacher and very knowledgeable. He has showed me a ton of stuff.
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    Member ptarmigan's Avatar
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    If you have used legos or have kids that do, you can figure out a jet unit. It's not genius material you just have to go for it, or you can pay somebody to show you. I always remember better when I figure things out for myself.

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    Best to learn how to do it yourself. You never know when you'll need to do that on a riverbank somewhere. If you run an outboard jet, you'll eventually need to do this in the field. I promise you that..... For me, I regularly check the gap between the impeller and sleeve and re shim fairly often depending on how much boating and what kind of conditions I'm boating in. For me personally, I need to stay up on it to eek every little bit of power out of my little motor that I can. It is a good idea to carry a complete set of spare washers, shaft nut, plastic sleeve, key, dog eared thrust washer and nuts for the foot as it is really easy to drop those parts in the water if you are working on it on a river bank. They are really hard to find in a foot of moving silty water. Remember that the shaft nut only needs to be snugged up finger tight. The dog eared washer will keep it from backing off. Also, when sharpening the impeller I've found that a broader duller edge is less likely to chip or crack if you suck some gravel through versus putting a really sharp edge on it. More than once I've had to pull the foot to remove a rock or stick lodged in lower unit. It is amazing how the smallest little rock or stick can have such a detrimental effect on performance.

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    Member ptarmigan's Avatar
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    Quote Originally Posted by bairdi View Post
    Best to learn how to do it yourself. You never know when you'll need to do that on a riverbank somewhere. If you run an outboard jet, you'll eventually need to do this in the field. I promise you that..... For me, I regularly check the gap between the impeller and sleeve and re shim fairly often depending on how much boating and what kind of conditions I'm boating in. For me personally, I need to stay up on it to eek every little bit of power out of my little motor that I can. It is a good idea to carry a complete set of spare washers, shaft nut, plastic sleeve, key, dog eared thrust washer and nuts for the foot as it is really easy to drop those parts in the water if you are working on it on a river bank. They are really hard to find in a foot of moving silty water. Remember that the shaft nut only needs to be snugged up finger tight. The dog eared washer will keep it from backing off. Also, when sharpening the impeller I've found that a broader duller edge is less likely to chip or crack if you suck some gravel through versus putting a really sharp edge on it. More than once I've had to pull the foot to remove a rock or stick lodged in lower unit. It is amazing how the smallest little rock or stick can have such a detrimental effect on performance.

    I couldn't agree more. Much easier to figure it out on your own in your driveway rather than in fading light on the river.

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    Member Bullelkklr's Avatar
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    I found a tutorial online that he was happy with. http://www.leeroysramblings.com/outb...aintenance.htm We pulled the old impeller out last year in the field and replaced it and shimmed it at about 1/16" and it seemed fine. He was having other issues with the motor. It is very easy.

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    Quote Originally Posted by Bullelkklr View Post
    Who in anchorage can check the shims on a jet outboard? My uncle has a 50hp effinrude with a jet lower that he wants to take to someone to check it out. It is pretty new - like 120 hours, but when we had issues with the motor (fuel line leak, fowled plugs) last year on a moose hunt we changed out the impeller hoping for a quick fix - - and we had never touched one before and are not at all knowledgeable with them...
    Look up Outboard Jets on line. They have printable instructions right there. If I recall, the clearance for aluminum impellers is .030. That's thirty thousandths of an inch. All filing should be done on the bottom edge of the impeller only. If you are running a stainless impeller .015, thousandths is recommended.

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    The tighter you shim it the less gravel can get in the gap and scar up the sleeve. But there's a limit. You can shim it so it starts in your driveway but jams when you put it in the silty Su. You need to learn to shim because if you use the boat much you'll probably need to re-shim a couple of times during the season, particularly if you run in silty water. The tighter the shim job the more thrust your motor will produce and when you run heavy, you can definitely notice the difference that one shim can make.

    I talked to Dick Stallman (Outboard Jets) several times through the years. I have always shimmed to a closer tolerance than what he recommended. Everybody I know does. It works better. I think he used to say to shim until the impeller made light contact and move three shims for clearance. I'd move one. Heck, I have a couple of friends that used to have half thickness shims made so they could fine tune even closer.

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