NS40C slipping at high speed (not the hub)

[Dterry84]

Hi all,

Same old story I took the boat out with a few friends and before I know it the engine is accelerating but the boat is going nowhere. At first I thought it was the prop so I swapped it with a new one, with no success. I also changed the clutch dog in which gave me some improvement in speed, but honestly I think I have a bearing issue. Here is a video I took after I replaced the prop and clutch dog.
Thanks, Dan

https://youtu.be/78FLLPIEPho

 

[pvanv]

If the motor comes up to RPM, but the prop does not, you have a bad prop. Period.

 

[Dterry84]

If that's the case where is the high pitch whine coming from? And should I be concerned?

 

[Sea Rider]

Was the whine heard before changing prop & clutch ?
Was gear oil level fully filled prior changing clutch ?
If water was not found inside gear case, should have 0 issues with inside parts.
There are 3 bearings inside gear box, it's good to inspect them when changing internal gear box parts.
If whine comes from bearing should be concerned if in a near future bearing will become jammed.
Inspect fuel pump diaphragm, if severely ballooned will give those symptoms at full hammer down, provided that prop and OB are 101% healthy and doing their homework right.
Is it possible to lower OB a tad or it's transom height is fixed ?

Happy Boating

 

[Dterry84]

Yes it was heard before changing the prop and clutch. It is more noticeable now than before. And yes the oil was filled completely to the top. I had a mechanic mess around with the timing and I have heard that a flywheel could produce the same whine. And I could adjust the angle on the outboard.

 

[Sea Rider]

By angle, you mean trim angle or advance timing ? That OB needs to run at 90? deg, as posted vid is good. Is prop correctly adjusted, must have a small play when pushing prop in, that's normal. But must not have play on prop shaft when moving prop back and forth, check, adjust as needed.

Happy Boating

 

[pvanv]

If you are coming up to RPM and the boat is not coming up to speed, the prop is bad. Now then, what is your RPM at WOT? and has that gone up or down?

 

[Dterry84]

Thanks for the replies the prop is sitting tightly on the prop shaft, I decided to get a new prop and will try it out soon.
At wide open throttle its around 5500 rpm, I would say it has gone up a 100rpm.
Still concerned with the whine that the engine is producing and cant help but think its related to my problem.
I'm in the process of taking apart the lower unit to further inspect the gears and bearings, I have already found that there is some major drag when trying to turn the drive shaft without the water pump on the shaft. The drive shaft carrier bearing was just recently replaced and it looks in good shape, my guess is that the pinion is not correctly lined up to the F/R gears? Love to hear your thoughts and thanks.

Dan

 

[pvanv]

There will be some drag from bearings and seals, but that should be minimal with the pump off. Since the clutch is a go/no-go mechanical dog, it cannot ever slip, unless it chatters. 5500 is a good speed. If gears were replaced, then the shim packs should have been re-done to get the correct backlash. That requires dial indicators, jigs, and time and patience.

 

[Sea Rider]

Are you replacing current prop with same new ? You are still 350 wot revs from max wot revs as usually loaded. Ideal is to run at near or max wot rpm, once there can throttle at the speed you like best while manintaining good plane. OB will work better thgroughout the whole thgrottle range. See if can buy same diam prop with one less pitch, will achieve better hole shot as loaded.

Happy Boating