For a good overview oof a marine transmision you might want to read this link.]
- our gear box will not engage the propeller shaft in forward, the engine runs fine ,
- but when we increase the RPM, the propeller shaft will not increase in speed .
- oddly when we put the engine in idle and we shift to reverse and increase the REvs in reverse (there is a horrible noise from the gear box) ,
- then we can go to idle again and then put it in forward and now the forward will work again
- for a few minutes
Alex, welcome to the SBO forum.
Seems you packed a lot of frustration into your first post. I have no idea about your knowledge on transmissions, so I apologize if this is too elementary.
I like to approach the issue with a simple mind set. The marine transmission is not like a car. It is a basic system. Three options Neutral, Clockwise or counterclockwise rotation of the prop shaft. The prop is free to turn when in gear.
Do you have a power/shift gear lever combination? Single Throttle/Gear lever set up or a gear shift and a throttle lever set up?
I tried to isolate the various observations in order to help trouble shoot the problem.
1 & 2. The transmission needs to mesh with the forward gear from the neutral. You state it will not go into gear. There is no sounds mentioned (like grinding of gears, screeching etc).
The simplest malfunction would be the shifting linkage. You are not in gear. Otherwise the prop shaft would be spinning and the boat would be moving. So the linkage must not be moving the shift arm on the transmission into forward gear.
3. When shift into reverse and then apply power (increase the rpms from the engine) you hear a horrible noise. That sounds bad... Does the transmission go into reverse? Are you moving backwards or at least churning the water tied to the dock.
If not just bad noise... Then gain the linkage may be the cause. With out isolating the noise (transmission grinding or the damper plate "between the transmission and the engine") it is difficult to identify a cause for the noise.
4&5. You go through this trauma with bad noise and you get forward gear to engage. This again could be linkage. I am not sure what "Will work again... for a few minutes" means. You get the prop to turn and you can go zipping about the water, but with out action on your part the transmission steps to neutral after the allotted time? That would be strange. If the linkage is loose or not aligned, I guess the transmission could slip out of gear.
With out the engine running, I would have someone move the gear lever, while you observe the transmission linkage to see if it moves the shifting arm from forward to neutral and reverse.
Then let us know what you observe. If it is as simple as tightening the linkage you should be able to correct the problem with a screw driver, or identify the parts that are failed and replace the linkage that is not working.
Good luck look for the simple failures before you call the yard and tell them your transmission needs to be overhauled.