Harmonics from jet drive

[victorfb]

Has anyone ever tested if the jet drive, and or driveline creates harmonics or extensive vibration that is transfered back to the crankshaft of the engine? since there is no gear mesh or rubber dampner between the crank and driveline and jet drive, i was wondering if there was a benefit to adding another dampner to the rear of the crankshaft. maybe useing another dampner instead of the aluminum PTO normally found on most (if not all)jets. with such a direct and solid connection to all the system, i would think there should be some sort of vibration transfer back to the crank. most other propultion sytems have a split of some sort. gear meshing, rubber couplers, ect. it just seems that alot of jet drive boats are susceptible to bearing wear and thought maybe another dampner could be a benefit.

[moneysucker]

Has anyone ever tested if the jet drive, and or driveline creates harmonics or extensive vibration that is transfered back to the crankshaft of the engine? since there is no gear mesh or rubber dampner between the crank and driveline and jet drive, i was wondering if there was a benefit to adding another dampner to the rear of the crankshaft. maybe useing another dampner instead of the aluminum PTO normally found on most (if not all)jets. with such a direct and solid connection to all the system, i would think there should be some sort of vibration transfer back to the crank. most other propultion sytems have a split of some sort. gear meshing, rubber couplers, ect. it just seems that alot of jet drive boats are susceptible to bearing wear and thought maybe another dampner could be a benefit.
I would think that the drive shaft u joints would help to absorb some. The transmission normally bolts direct though. I have heard thet you are supposed to have 1* in the driveline not completely straight so that the shaft is not floating and vibrating.

[bordsmnj]

i thought it was 3* and that it was to keep the univ. joint evenly loaded? but i don't know much about jetpumps

[Brooski]

i thought it was 3* and that it was to keep the univ. joint evenly loaded? but i don't know much about jetpumps
I thought it was the jet boat drivers that were supposed to be loaded....

[bordsmnj]

mmmmmmmmmmmmcould be :idea:

[SmokinLowriderSS]

I thought it was the jet boat drivers that were supposed to be loaded....
HEY! I resemble that remark!!!!

[Mighty Thor]

ok, the reason you angle the driveline is to make sure that the U joints move thus rotate the roller bearings thus preventing them from sittin in one spot and rubbing flat spots were round ones should be. as for loading the drivers, you can usually do that by pushing them off the edge of the dock. Of course it helps if you park the boat there first, but it aint absolutely necessary.

[Cs19]

Ive also been told jet-drives are hard on bearings and cranks, just balance your driveline, have the jet-drive balanced if your impeller is SS or MAG and have sufficent end play in the driveline and you've done what you can.

[victorfb]

Cs19. that makes sense with the use of SS and bronze imellores. thus adding more wieght that may or may not be out of ballance. thanks for the tip.

[DeputyDawg]

One reason jets are hard on bearings is because the motor is always under a heavy load. I can't think of any other application where an engine is under so much stress throughout its life. It's kind of like making dyno pulls all day long at the lake.