I had the same issue with a tohatsu 3.5hp (same engine). I bought it new and filled it from the bottom oil hole until it filled the gearbox and came out the top hole, it was perfect for many years, then one year when i changed the gear oil the top hole gearbox became blocked. I took the prop off...
I found this on tinterweb.
Love the comments on the report,
A spokesman for Teignmouth Harbour Commission said the incident was relatively minor and should not have happened...
The 25,000 tonne ship, which carries general cargo, was on its way from Rotterdam when it appeared to take a wrong turn.
Cargo vessel Clarity gets it wrong and runs into the Visitors moorings at Teignmouth, hope no one was on board the yachts. Might have been much more serious in the summer.
Agree, its a pig of a job, after taking the gearbox off my tohatsu 3.5hp (same engine) a number of times, ive worked out a few thing to make it relatively stress free, firstly reattach the lower unit with the engine vertical not at an angle and certainly not horizontal. Attach a piece of wire...
Have you checked the oil level, also does it have the correct oil spec for the gearbox, when was it last changed, if its unknown to you it would be worth changing the oil for some fresh before you condem the box.
We chartered a yacht from Flamingo Yachts recently, during the week one of the party was at the mast attending the sails inadvertantly stood on a hatch cover and broke it. We told the company of the damage and was amazed when we got a bill for £500 The hatch is a flush fitting 10mm perspex...