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Old 11-03-2021, 12:55   #16
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Re: Motor runs well but little forward propulsion?

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Originally Posted by SteelCruiser View Post
reverse is no different -
Couldn't venture a guess without a diagram of the transmission but if they use a cone clutch and a band for reverse it's probably a sun gear and the clutch cone may very well be worn out. Getting stuck in gear is fairly common as cone gears wear out also. I'd still check the fluid for brass or shavings of any kind but it sounds like either the coupler between engine and trans is gone or the problem is internal to the transmission. But this is just an educated guess on my part.
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Old 11-03-2021, 13:32   #17
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Re: Motor runs well but little forward propulsion?

What purpose does the round metal bar serve?

It looks like an emergency shift arm in case the shifter cable between the steering pedestal and transmission fails. I would remove it.

IF you have friction cones in your transmission, they may be "glazed".

My two cents..
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Old 11-03-2021, 13:57   #18
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Re: Motor runs well but little forward propulsion?

It’s a manual gear box ,the engagement lever must be adjusted from time to time as the cone clutches wear ,failure to adjust just increases the wear factor until you loose drive ,the gearbox must be removed to re build or re face the clutch cones ,lever travel must be adjusted from time to time not a biggy ⛵️⚓️
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Old 11-03-2021, 14:13   #19
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Re: Motor runs well but little forward propulsion?

Disconnect the shifting cable from the reverse gear lever [correct name], some call this a gear box shifter, and move it forward, you should have a distinct indent click, unless it's a hydraulic design.
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Old 11-03-2021, 14:21   #20
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Re: Motor runs well but little forward propulsion?

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Originally Posted by Dougtiff View Post
Disconnect the shifting cable from the reverse gear lever [correct name], some call this a gear box shifter, and move it forward, you should have a distinct indent click, unless it's a hydraulic design.


I’m not sure I’d call it a “click” on that type of box. More like a forced thud or clunk when the lever is pushed over the detent r
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Old 11-03-2021, 17:58   #21
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Re: Motor runs well but little forward propulsion?

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Originally Posted by SteelCruiser View Post
prop not foul.

the Prop spins freely in neutral.
Today I will put in ‘Fwrd’, then jump into water and see if the prop still turns. Q. It ought not turn then = correct?

Is there any possibility there could be a ‘key way’, holding the prop on, that is sheared, allowing the prop to spin , in gear?

If you put it in fwd & it still turns it doesnt mean the clutch is not slipping, it just slips more under load.
If you had a sheared key it would likely have no drive at all.
As scubaseas says drain oil & check.
Our lister gearbox ( different engine ) had a fibre cone clutch so brown particles in oil.
Again do you have any model & manufacturer plate on gearbox?
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Old 11-03-2021, 18:03   #22
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Re: Motor runs well but little forward propulsion?

Quote:
Originally Posted by Dougtiff View Post
Disconnect the shifting cable from the reverse gear lever [correct name], some call this a gear box shifter, and move it forward, you should have a distinct indent click, unless it's a hydraulic design.

Another vote for this, I suggested a similar step earlier but this is a better way, disconnect remote control first, just use the lever.
If you can get another person to push the lever forward whilst you are motoring & it speeds up you confirm a slipping clutch.
There are some places that can put a new friction lining on them if you cant buy the original or its a ripoff.
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Old 11-03-2021, 18:47   #23
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Motor runs well but little forward propulsion?

dive under the water

1. motor not running
a) in neutral ? prop spins freely
b) in foward? more difficult, yet still fairly easy to turn by hand
c) in reverse ? not possible to rotate prop by hand
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Old 11-03-2021, 19:55   #24
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Re: Motor runs well but little forward propulsion?

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Originally Posted by SteelCruiser View Post
dive under the water

1. motor not running
a) in neutral ? prop spins freely
b) in foward? more difficult, yet still fairly easy to turn by hand
c) in reverse ? not possible to rotate prop by hand

Yep that sounds like slipping clutch. Have you got someone who can push the round bar lever fwd with the cockpit control disconnected whilst you perform the same test in fwd?
That clutch adjustment is real bad or the clutch is worn out.
May be a plate clutch, you need the gearbox exploded view as Scubaseas suggested
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Old 12-03-2021, 00:42   #25
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Re: Motor runs well but little forward propulsion?

External bowden casing has slipped, so that the cone clutch for only one of the directions is being engaged.
It's just re-adjustment of the cable-end and Bowden grip that are needed.
Frequently the result of an inadequate mechanic, with inadeuate eyesight and inadequate patience.
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Old 12-03-2021, 06:34   #26
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Re: Motor runs well but little forward propulsion?

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Originally Posted by chasfgr View Post
External bowden casing has slipped, so that the cone clutch for only one of the directions is being engaged.
It's just re-adjustment of the cable-end and Bowden grip that are needed.
Frequently the result of an inadequate mechanic, with inadeuate eyesight and inadequate patience.
Good point. This is indeed possible and a good thing to check if the OP had Bowden cables but it looks like he is getting full engagement. I agree with Compass 790. Sounds like forward clutch is slipping.
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Old 26-04-2021, 04:05   #27
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Re: Motor runs well but little forward propulsion?

Just got back aboard. more info
The LH150 reverse gear box?
Absolutely no oil showing on the dip stick. :-(

The reduction box has thick black very dirty oil.
looks like the sort of oil in a diesel engine that desperately needs an oils change.

I will obtain gear oil for the reverse gear box and top up tomorrow.
The drain plug for the reduction box is seemingly impossible to reach, down and under - there is no room.

Q. can I use of of those ‘suck’ type pumps to suck the old dirty oil out and then put in fresh oil?

Q2. What do we think of a product like ‘Lucas Transmission Fix Stop Slip’
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Old 26-04-2021, 04:11   #28
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Re: Motor runs well but little forward propulsion?

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Old 26-04-2021, 06:11   #29
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Re: Motor runs well but little forward propulsion?

Quote:
Q. can I use of of those ‘suck’ type pumps to suck the old dirty oil out and then put in fresh oil?

Q2. What do we think of a product like ‘Lucas Transmission Fix Stop Slip’
Suction pump will work fine

Stop Slip may help but would not be a permanent fix. Works more for conditioning rubber seals than friction discs. Having said that I got one more season out of my Volvo reverse gear by using Stop Slip.
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Old 26-04-2021, 15:54   #30
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Re: Motor runs well but little forward propulsion?

On my Yanmar box, both the box and reduction gear use the same oil, SAE 30 engine oil.
Though there is a drain-plug underneath, it's not accessible, so
I use a vacuum pimp, though the dipstick hole to get most of the oil out. It never seems to get dirty or change in any way, so rather than changing it avery other engine oil change, I do it for the 1000hr ones.
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