Advice needed with Self Changing Gears gearbox

[petehitch]

I have a Gardner 6lxb turning a large 2 bladed prop through a SCG 4.5:1 box. This has worked well for 15 yrs. The engine is fine but now will not reach anything above half revs when manouvering or cruising. I thought it was a rope around the prop but have checked thoroughly. Would this be a fault with the gears??
Any advice would be appreciated.

 

[Stoaty]

I have an SCG gearbox and manual. It looks likely that the drive plates (like a car clutch) are worn and need replacing. Before doing that check you have enough of the CORRECT oil in the gearbox. It has to be straight 30w with no detergents. Comma sell it as classic 30 about £11.00 a gallon from my local motor factors. Detergent oils can cause foaming in the gearbox apparently.

Edit

After reading you post again. It's unlikely to be the gearbox if the engine is not reaching full revs.

 

[WindermereColvic]

Will it reach full revs out of gear? I would suspect a fuel issue, ie, not enough reaching the engine, are the filters clean?
Matt

 

[petehitch]

Thanks for advice. I have now changed all fuel filters, Racor primary and 2 on engine.
The engine reaches full revs out of gear, but not in gear forward or astern. The shaft turns freely by hand. The gearbox oil is fine and have just changed filter. I am worried about causing damage to the gears or seizing??