Do you think a more modern prop with the same pitch would help at all? The prop has a few nicks from the previous owner that I've ground even, but they look pretty true. I was just curious if the modern three blade props that I see for these old motors give any noticable performance increase over the original two blade props. Might be worth the $90...but I'd really like a 9.9 in the same era so I can still troll with it. I've never heard any complaints about these Evinrudes from the late 60's/early 70's. I'm usually running a mile or so to my fishing spots so speed is a little important and dependability is a must since I'm in remote areas...in the winter.[/quote]
Hi de hoog,
I do not have a lot of first hand experience with props and how they can improve performance. But, its a topic ive been reading about because the prop on my 20 hp Johnson is pretty banged up and needs to be replaced. I'll be buying a new one in the spring. From everything I've read a banged up prop will hinder performance and fuel efficiency in a big way. I'd say it is likely worth replacing and you'll see a difference. Just do your research on which prop is right for your motor... factors such as pitch and size etc...
Also, I was going to mention have you tried trimming your motor at different angles to experiment / optimize speed.
My uncle has a 80's evinrude 9.9 hp and the performance over the 6 hp is very noticeable. Substantially more speed / power. The other thing you can do with a 9.9 is put a 15 hp carb on it, most 9.9 evinrudes are compatible with a 15 hp carb. This would increase your power even more for a very reasonable price. With regard to engine reliablity, you're right... the 70's vintage motors are bullet proof. Needless to say , One of my contacts through work is BRP trained marine mechanic with a ton of experience with outboard reapiairs. claims the 80's evinrude products are rock solid as well...