I don't know if it's the EFI version or the Optimax.
But I would have a look at the ignition powerpacks and see if that's the issue.
I've seen some of the symptoms you have had with one of both powerpacks on their way out.
Let us know if you figure it out!
On my aluminum boat there is a small metal tag attached to the right hand side of the transom on the back. The standardized tags started in 1972 in the U.S. So I would guess either your boat is older than '72 or the tag is missing...
There is really not a standard hard set rule, for height for mounting an outboard motor on most transoms. In fact, some boats have jackplates which allow the owner to either manually, or electrically adjust the height. The height of the motor on the transom definitely can affect...
I wish I could remember the name of the salvage website I used. They were great to deal with. They also had an oddball tool that was needed as well. I think they had a location on the west coast and also one in Vancouver.
Let us know how you ultimately make out!
A number of years ago I was looking for a part for my old 60's Merc. The part was actually obsolete. I used an online marine salvage and was able to get the part from them.
Have you tried looking at that approach?
It almost sounds like it’s not the same pitch.
Is the diameter the same size as well?
Some places will have some spare props around you can test with. I’m not sure where you bought this one. You could also mark the prop just to make sure the hub isn’t slipping.