Re: 18HP saga continues. Can’t get past 14mph and 3,900 RPM.

[stephenspann27]

quote fleetwin:

quote BillW:

I know you have tried three power heads. However I still would like to know the compression. 18s are unstoppable and get used and abused until the cows come home. Thus, they are often found with high cylinder wear. They will still run like a fine Swiss watch at lower speed, even with this wear. If you haven’t got 115 psi or better, you may not ever make it to 4500. Many times, you see them with 90, even 80 psi compression and they are smooth as silk; but the power just isn’t there.

At this point, you have been whipping this thing forever; so it is more of a matter of pride than money, that you get it to work. If I were you, I would rig it up with an adjustable high speed jet carb bowl or whole carb, at least as an experiment and see if that helps.

I like this idea…..The high speed needle might be too long and interfere with the lower pan though…
I have quickly reread this thread, but I don’t see anything about the prop style/pitch, pictures of the boat, or a description of the tachometer you are using….15MPH does seem way too slow for an 18hp though, have you tried it on a different boat?

Around January last year I had this rig out, along with my father in law’s 14′ flat bottom, which is bare bones, and his 1990 15hp evinrude. I did swap the motors and boats around at that point. I think my boat ran 19-20MPH with his 15hp. I don’t remember for 100% sure what my 18hp pushed his 14′ flat bottom to, I think it was around 15mph. He is boat has less drag for sure, and is probably lighter.

As far as the adjustable carb fitting my lower plan. There is already a hole in the pan I think the bass shaft can go through. I’ll enlarge it if i need to. I’m determined to make the older style carb work.