Clamped off oil line

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Water Crafts
97 challenger 1800
#1
So I bought this 97 challenger 1800 a little over a month ago knowing I had to do a top end rebuild on one of the engines but as I’m tinkering around in the engine compartment this past week I notice one of the oil lines coming out of the oil tank is clamped off. I’m new to the Rotax engines but I’m told this is not a good sign. Most likely it’s my rotary valve seals leaking. My question is do I unclamp and see what happens or do I leave it clamped? If I leave it clamped for the season what damage is it going to do to my engine or is the damage already done and at this point I’m just waiting for a failure?
 


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Water Crafts
2001 Sportster LE 951 Carbed
#4
If not converted to pre-mix then oil from the tank will feed both the oil injection system (the pre-mix option) and the rotary valve gear where the crankshaft oil seals can be worn and flood the crankcase with oil as the engine sits unused.

The quick fix for leaking crankshaft oil seals is to clamp the line so the crankcas won't be flooded with oil but you must remember to remove the clamp before use or risk damaging the rotary valve gear (due to lubricant starvation).

A cylinder compression check (using a compression test gauge) is your friend to let you know when a rebuild is a necessity.

FWIW, the engine is old assuming it's original thus the seals are questionable and this can lead to other problems besides flooding crankcase with oil such as air leaks which cause the engine to run lean and burn pistons.

If the engine hesitates during operation, this indicates fuel starvation and at a minimum the carburetor(s) should be overhauled if the compression is acceptable. Fuel starvation (running lean) leads to overheated, melted pistons.
 
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Water Crafts
97 challenger 1800
#5
Well that could explain why I had to rebuild the top end of the engine. The person I bought the boat from only had the boat for a little while and when I contacted him about the clamped oil line he had no clue about it so I can assume he did not unclamp the line while using. I just wish I would of known about this before I rebuilt the top end so that I could of just went ahead and rebuilt the entire engine.
 
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Water Crafts
97 challenger 1800
#6
That you for all your help. This is my first jet boat and this forum has been my best friend. Lol
 
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Water Crafts
2001 Sportster LE 951 Carbed
#7
Hi, I just saw your post so sorry I didn't reply earlier.

Just to reiterate a little bit in case I wasn't clear....

If the outer crank seals are leaking enough air inwards the engine will run lean and this leads to burning pistons. Either this, or carbuetor/fuel system issues can cause the fuel mixture to be too lean (roast a piston or both).

Your clue of carb issues will be hesitation during acceleration, probably the engine will fall on it's face. Bad outer crank seals can cause this as well but it's common for carbs to be corroded and it can be a challange to get them operating properly without knowing what to look for and how to remedy (part throttle pilot holes clogged and or corroded/ thoroughly clean, blow with air & ream them out as necessary).

Your clue of crankshaft outer seal issues is often idle inconsistency and hard starting.

Your clue of inner crank seals will be oil flooding of the crank case (thus the shutoff valve workaround)

As long as the engine runs properly and compression remains good the engine will be fine but if it lean-hesitates then piston failure is gonna happen b/c that makes lots of heat that destroys the oil film.
 
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Water Crafts
97 challenger 1800
#8
So as long as everything is running ok then all I need to do is unclamp the line during use and then clamp it again after I’m done?
 
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97 challenger 1800
#10
Thank you everyone for all your wisdom. My family has owned prop boats my whole life and for some reason I decided this time I was going to by a jet boat and I must say it is really kicking my ass! Lol still have not been able to get it out on the lake working properly but I have hope!
 

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