Is my gearbox faulty?

[Ken13559]

Previously I suspect my Kiwi Feathering Prop did not feathered over fully when I go reverse, resulting in very heavy load on the engine causing some black smoke and rpm cannot go beyond 1000rpm. Even with clean prop, ocassionally after going forward, I put it to reverse and the engine gets very loaded. I'm beginning to suspect the gearbox to be a problem. How do I check for this easily? I've Yanmar 2GM20F with KM2P gearbox.

 

[JohnShannon]

Talk to Kiwi read the documentation etc. I have a Kiwi prop, pitch in the forward direction is adjustable, but in the reverse direction is fixed, and maybe a bit coarse. I think this is the prop.

Mine works great, but reverse seems to be one of the tender points with the design.

 

[kloudie1]

Ken, it is highly unlikely that there is a transmission problem.. Everything that turns when in forward, turns in reverse also.. when the engine is running, all the gears are all turning some are connected to the shaft and some not.. I would suspect the prop first.. Secure the diesel fuel cutoff, put the tranny in neutral, and dive on the prop.. twist it around from fwd to reverse.. using hands on blades and then using the shaft as the engine would. You will see the problem.

EDIT: The one thing that might do this is if the forward clutch is not fully disengaging when the reverse clutch is engaged.. Make sure at the transmission that the lever is clicking solidly into the neutral detent.. This problem would be highly unlikely and you could detect it by uncoupling the prop shaft after one of the events and then starting the engine and shifting into reverse... If it is the transmission, the engine would load .. again, this is very unlikely.

 

[Ken13559]

I've checked the prop feathering by turn each blade, no problem, which makes me wonder if gearbox to be the issue. To solve the reverse load problem, I've to engage forward and then reverse again. I'll check the gear shift alignment. I could also push the decompression levers and pull the stop knob, remove the gearbox dipstick and look inside while cranking the engine in fwd and rev gear. Think I'll see anything?
Thanks.

 

[Chris Patterson]

I doubt that you would see anything of relevance. If it were me, I would carefully drain the oil, and put it in a glass jar. From there, you can sometimes tell a gearbox's health. Not very "scientific", but more of an old school determination. Drive train components generally leave a footprint when they're going in the hole, ie: some type of "garbage" suspended, floating, or settled. That's just a five dollar check, with the benefit of getting the oil changed..

 

[kloudie1]

I am with Chris on this one, Ken.. You'll see the same thing in forward as in reverse.. a few teeth ends spinning happily.. If the clutch is not disengaging, the oil would be pretty black from the bronze clutch wear.. Ya might try taking the control cable off and making sure it is clicking into the detents .. you should be able to turn the shaft easily by hand in either direction when in neutral. In reverse, you should be able to turn the shaft backwards with some resistance but not forward without turning the engine .. in forward, you should be able to turn the shaft forward with some resistance but not backwards without turning the engine.. That is about as comprehensive a check as can be done without a disassembly.. Good Luck..

 

[JohnShannon]

Ken

The reverse pitch is steeper than the forward pitch so the load at any given shaft RPM is higher. So the prop may be working perfectly, but not be a good match to your boat/engine/gearbox setup. When I bought mine, Kiwi wanted all that data, engine HP engine RPM and gearbox ratios in FWD and Reverse.

 

[Ken13559]

I'll check the oil. I'll try hand spinning the shaft. I gave all data required for the kiwi prop. Was 16"Dx20deg P. I had to dial it down to minimum 18deg. Anyway, reverse is a fix 23deg.
One other thing I could do is swap in my spare Flex-O-Fold. I never had reverse problem when use FOF.

 

[Claude L.-Auger]

I'll check the oil. I'll try hand spinning the shaft. I gave all data required for the kiwi prop. Was 16"Dx20deg P. I had to dial it down to minimum 18deg. Anyway, reverse is a fix 23deg.
One other thing I could do is swap in my spare Flex-O-Fold. I never had reverse problem when use FOF.

Good idea Ken, if the FoF worked perfectly then put it back on and go try it in forward in reverse. That will immediately tell you if it's the Kiwi prop not matched properly or the tranny acting up.

 

[Ken13559]

Just got the FoF in. No problem reversing. Will check over next few weeks. Btw, the Kiwi I removed, one of the blade is alittle stiff going reverse. Not sure if that is the cause of heavy loading in reverse, but it seems like it needs some grease inside of the assembly. Anyway, I'll know the result in couple of weeks. Oh, sharks! I lost a socket and wrench handle in the process. It's either that,the 3-pronge extractor or the prop. As I have only 2 hands, well answer is obvious. Next time I'll tie all items with a cord. Lesson learnt.