Gearbox Problems :-(

While you're there, get full details of the g/box that's on the engine. Ratio, manufacturer etc. Take lots of pictures of things.

One way to see if the shaft is slipping in a coupling is to mark both shaft & coupling with a paint pen, Pentel pen etc. If the marks move out of alignment, something is bad. Doesn't help if the prop is spinning on the shaft but same thing applies, just harder to mark.

Do you have a hand held tachometer that uses tape etc to give you a readout? Useful bits of gear as you have a way to determine both engine RPM and g/box output RPM - assuming things are reasonably accessible.

Down the Tasman Peninsula is a long way. I could rent you a mooring out the front of my place for 6 months or so, I'm only 35 minutes from Hobart and 10 minutes from Kettering.

PDW

 

I have little to ad, and might be totally irrelevent, but since the answer is not found yet, I will toss my ideas in because who knows, they might lead to a real idea.

-Some transmissions have trolling valves, that allow low pressure on the clutch to spin the propellor slower at idle. This sounds like what you experience, so it might be possible that you have low clutch pressure.

-I can't imagine the prop would spin anywhere near fast enough to get 2 kts of speed, if a coupling was stripped. I think it would just spin and get looser and looser real quick.

In auto transmissions, a certain spec of fluid is needed. And in locking differentials, a friction modifier is added to the oil to make the clutches grab enough. Maybe the incorrect fluid is in transmission?

I don't know much at all about marine transmissions, but I bet it is the transmission, and I bet it is an issue with the fluid, or pressure on clutch.

 

Well just a quick update. Went down and checked all the suggestion regarding the coupling and could not find any slippage there. I was unable to verify if the prop is slipping on the shaft, but have now been able to bring the boat closer to being able to get some help.
Thank you to all that shared there ideas and thoughts to help solve this problem and I will update when I am able to resolve the issue.
Thanks for all your help.

Cheers Jerome

 

hi jerome. I did a bit of searching on lomatec and got a little bit of info. Apparently the engines are ok but the factory fitted water pumps and gearboxes are rubbish. The lomatec agent in croatia said that he replaced the waterpump and gearbox on each engine he imported with quality brands like johnson and prm. So if thats correct you may have to ditch your gearbox and fit a better one. To me a better option would be to sell the engine and box and fit a good secondhand yanmar. Or 1 of the other good brands. If it turns out to be a gearbox problem.

 

its not a hydraulic gearbox at all. And props can slip on broken key and still push a boat. Experienced people know this.

 

Thanks Brendan,
Yes I've heard that there an obscure engine but very cheap. I will continue to find the problem with the issue and hopefully get it resolved. At least the boat is closer so getting to it and those who are knowledgeable is this field will be much easier. I will re-post any finding once I find out.

Cheers Jerome

 

At least if it is the box it must be an sae flywheel housing which makes it easy to bolt another box in. Hopefully it will be something simple anyway. Let us know what you find.

 

The best diagnostic test is if you can measure the shaft speed - I mentioned digital RPM meters in another thread and PDWiley did as well - these have come down to the point where it can turn a problem like this into a such a simple excersise. Simply point at the motors crankshaft pulley to get an exact RPM ditto on the shaft and bingo - if the two numbers are multipliable by the gearbox ratio then all is good through the transmission and your prop is slipping - fix prop, if less than it should be - fix box.

http://www.amazon.com/Digital-Photo-Laser-Tachometer-Contact/dp/B0045E0GT2

At those prices it's crazy not to have one BUT if you're out in the boonies you may not find that such an easy option.

However, there are many 'GoPro' camera's about and they can actually shoot in high speed e.g. 120 frames per second. you could mark your shaft with a marker (say a thick spiral) and 'film it' - typically diesels run at 2-3000 rpm with a 2:1 gearbox.

So the camera will be shooting 7,200 frames a minute and the shaft should be turning at about 1000, you could use that footage to verify the shaft speed, with some simple maths.


Thanks for keeping us in the loop, and best of luck.

 

the simplest check is lock the prop and try and spin the shaft with stillsons. no need for spending money on all that stuff unless he has a use for it later on. if you know what you are doing you can flick the starter instead of using tools. but after reading up a bit I think it will be the gearbox. it is a manual box and is probably out of adjustment or had a failure.

 

just had another thought Jerome. have you tried reverse to see how fast
it goes. the reverse band locks the planetary drum and that's how you get reverse . if reverse is good then the problem will be in the gearbox most likely. if not it will be from the red gear back. like par said, a mechanic will find the problem quickly.

 

I know where there's a Kanzai box off of a Yanmar 2QM but it's only 20HP or so. Probably a bit light for that engine.

There aren't many possibilities - I'd be checking the drive system before I bothered looking at the prop, but I'm lazy and allergic to cold water.

There are a few engines on Gumtree ATM.

PDW

 

Thank you all for so much for your informed suggestions regarding my problem.
I now have the boat close to the city after a very stressful tow from Port Arthur. I will now be able to get a mechanic to have a look and hopefully diagnose the problem. As for getting in the water I think I will put her on the slip.

Thanks once again for your support and I will let you know what the outcome is as it happens

Cheers Jerome

 

Any updates on this issue?

Curious...

 

Hi WestVanHan, and everyone who have been following the issue I have had with Leela Belle.
Well just before Christmas I got to slip Leele Belle. It was then we found the problem (hopefully). Once she was out of the water we were able to get a close inspection of the propeller. It seems the only problem with it is that it was not pitched to suit the boat. Once out of the water and washed down I took the prop off and visited a local engineering firm and it was confirmed with the information regarding the boat, they confirmed it. The pitch on the prop was 16 X 10 and is now 16 x 11.8. i am waiting for the slip to become vacant so I can re install the prop and do a sea trial to confirm what appears to have been the issue. It appears the previous owner didn't think there was a problem, why I don't know. I will post more info once I have had a sea trial, but feel confident that it will be all good.
Thanks to everyone for there help, which I have found invaluable.

Cheers
Jerome

 

How dirty was the bottom. Because a dirty bum would be most likely the problem if there is no mechanical fault. A 1.8 inch pitch increase may help but I doubt the po would have put up with a 2 knot top speed.