At random engine wont rev all the way up. 40hp 1960 evinrude

I was given a fiberform last year that has a 40hp 1960 Evinrude on it. It wouldnt start so i replaced, all hoses, spark plugs, coils, plug wires, points, and the water pump. I got it running and it start right up and idle perfect. I brought it out to the water, got it warmed up and the boat went along nicely. I got it to rev up and the boat planed out nicely. I then fished for a while and the engine started right up and idled nicely again. I could out the engine in foward and get it to rev up but not all the way. I just couldnt get it to plane out. I seems to be happening randomly and sometime when I do get it to plane out the engine run great and then begins to slowly rev down with my still hold the throttle open. The things I have to tried in fixing this problem are, open engine cover while my wife drives, take engine cover off, adjust idle screws while going, adjust linkages, and pump the primer bulb while going. None of these seem to work. This has led me to believe the carb needs a rebuild. Does this sound like what it may be? Any other suggestions?

Also on a side note when I go the boat from my dad he was saying the boat would go in reverse fine but would jump in and out of foward. I took apart the lower end when I first got it to check it out. But I truthfully didnt know what I was looking for, i work on airplanes. Well I put it back together and it runs fines in foward but jump in and out of reverse. Does this sound like I put the clutch dog in backwards from how it was. Should I replace it? Also not water is leaking into the lower unit but I now have oil that drips our requiring me to top it off everytime I take it out and keep a bucket under it when in storage. Any ideas on fixing the leak?

Thank you very much.
Kyle

Re: At random engine wont rev all the way up. 40hp 1960 evinrude

Jumping in and out of gear can be either or two things: 1) misadjusted shift cable or 2) worn clutch dogs in the lower unit. Total disassembly is required to inspect and/or replace clutch dogs. Shift cable adjustment is not a "fiddle with it" process. There is one correct adjustment. Shift lever in neutral. Disconnect cable at the engine. Shift lever on the engine in neutral. With the cable secured in it is fixed mount, bring the end of the cable up to the point where it connects to the engine. Do not pull or push on the cable to try and align the attachment points. If the cable does not line up, adjust the trunion (the threaded part of the cable sheath) until they do line up. Attach the cable. That's it. If it still jumps out of gear, disconnect the cable and try shifting manually. If it still jumps, you are in need of lower unit service.. If it behave properly with the cable disconnected, then you may have done the cable adjustment wrong or there is an issue in the control box.

Re: At random engine wont rev all the way up. 40hp 1960 evinrude

I adjusted the cable like that when I had taken the lower unit off the first time. I guess it will have to take it off again and check out the parts a little more in detail. Any idea about the engine part?

Re: At random engine wont rev all the way up. 40hp 1960 evinrude

Sounds like you replaced all the ignition parts, so you should have spark on both cylinders. Might want to check to be sure. A carb rebuild wouldn't hurt if you haven't done it. The other possibility is a failing fuel pump. Try pumping the bulb in the fuel line when it hesistates and see if that helps.