Part #376073- Johnson Pinion shaft shock absorber questions

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johnboy65

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Does anyone know what the correct length of a #376073- Johnson Pinion shaft shock absorber should be? Do they expand in length when the interior spring breaks and is there a way to check them before you purchase or install a replacement? I own a AD-10 that runs like a champ until you give it some throttle and then it acts like a spun hub.. I've tried just about everything to get this motor to push so this is my next stab at it..
 

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racerone

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It gets longer and jams when spring breaks.---Remove housing below the pump and inspect for damage.----Sure it is running on both cylinders ?
 

F_R

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That is NOT the spring used in the shock absorber. It is the neutral clutch spring used on TN models.
 

johnboy65

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racerone The motor runs and the throttle advances just fine. It will propel the boat at a low rpm or idle but as soon as you advance the throttle and put a load on it.. the rpms rev and the boat goes nowhere..
 

racerone

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No rubber hub in those props.-----Perhaps the transom is too high.
 

oldboat1

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You've been working on it for a while: http://forums.iboats.com/forum/engi...ards/9995106-johnson-ad10-wot-issues-1956-7-5

I stand corrected on the spring. Not sure that it's a shock absorber issue, though (binding a more likely symptom, not revving -- as mentioned in the earlier thread). Seemed to be an earlier consensus that air/fuel mix might be the problem.

Transom height or a mounting issue is worth exploring, as just mentioned (maybe trim adjustment too).
 

F_R

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It is entirely possible that the shock absorber spring is broken. Kind of depends on where along it's length it is broken. An inspection is in order. There is nowhere else to cause slippage under power except cavitation or ventilation as already suggested.
 

lindy46

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Is it possible someone put a rubber-hubbed prop on it sometime in the past and it is slipping?
 

F_R

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I suppose that is possible. They would have to change the prop shaft too. Original prop's drive pin was at outer end of shaft, rubber hub prop's drive pin is next to the gearcase.
 

johnboy65

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Prop is a shear pin 2 blade (no rubber).. Motor is a short shaft on a 14' tracker topper jon boat with a 15.5'' transom.. I've had it apart before, pulling the head, replacing the impeller, all new seals, o-rings, spaghetti gasket etc.. Just to have the same results happen.. I'm now thinking about purchasing a used shock absorber and just wanted some input wondering if I may be wasting time and money.. I do appreciate all the theories,thoughts and analysis..
 

F_R

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The shock absorber can be tested--if you have the proper test fixture. Very few people do, including me. A shade-tree method is block the propeller with a piece of wood and see if you can rotate the flywheel while in gear. Realize you would have to apply the power of 5 horses to get any meaningful results. Do not do it by turning the flywheel nut. That will over tighten the nut and destroy the flywheel. Use a strap wrench.

But the preferred way is to remove the part and inspect it. If it shows heat damage on the end, it might be broken. But not necessarily. It could just be expanded from grinding up rocks. I clean out the inside real well, then get it out in the bright sunlight and peer in there to see if the spring is broken. It is a real fat spring and you can see the broken ends---if they are not out of your viewing range. And depending on where the break is, you may be able to just pull it apart. Don't pull it apart if it doesn't come fairly easy.
 

johnboy65

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Thanks F_R I'm waiting on a used one I purchased on Ebay and another set of gaskets. Hopefully I'm not buying a broken one and wasting $40. Wondering if I could take the old one, if its broken, and weld it together. I know it's designed to be a safety feature for the motor but so is the shear pin.. This feature seems to protect the shear pin which is much easier to replace than this pinion shaft..
 

F_R

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Lots of people say to weld them together, then use a brass shear pin. All I can tell you on that is that when I welded one, the heat distorted it way out of alignment, which made it worthless. Perhaps it was just my procedure, I haven't wasted my time trying it again.
 

boobie

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Maybe I missed it, but does anybody know the length of that shock when it was new ???
 

oldboat1

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appears to be a little over three inches -- overall seven inch length for the absorber and shaft (#3, above). Think I have one on a shelf somewhere....
 

F_R

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6-3/4" seems to be the accepted number. I have a couple that measure a tad less at 6-11/16".
 

HighTrim

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6 11/16" is perfect or NOS.

6 3/4" will work but a tad tight. If you are going to press it back, aim for 6 11/16"
 

johnboy65

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Finally had some free time to work on this and all my gaskets and parts to do it. Thought I'd give an update. You all have contributed and helped and it is appreciated. Look what I found..
 

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