1968 20 hp wont crank out RPM's

[Harry B.]

It idles like a champ, but wont even come close to WOT.
It will go about half rpm's and sound like its bogging out and actually and eventually will loose some rpm if I stay on the throttlle very long.
I've torn apart the carb and cleaned it out good taking extra time examining the high speed nosel and giving the whole carb a good going through. Its got the smallest prop (9x9) for the 20 hp.
I wondered about the fuel pump I bought for it (the original was shot when I bought it), but it states that it is good for the 18 and 20 hp's of the era (pump #304089).

Anybody suggest anything that I can try to get my boat up on plane??? I've run out of idea's and need some advise.

Thanks in advance for your help!!!!!!!!

 

["G"]

Re: 1968 20 hp wont crank out RPM's

Harry,
I have one of these beauties sitting in my garage. It ran on the old pressurized tank. They had a FP upgrade that required drilling a port in the exhaust port cover I said I was going to do that but never did.

Assuming yours is upgraded to a vented gas tank I'd say you have a fast idle circuit/jet issue or a FP issue. If it didn't idle or run well I'd say check compression and reeds. Be sure the timing (point setting) is correct and it ought to scream.

I'm wanting to sell this one if you need one. It hasn't run for years but the lower end was rebuilt before it was put up. All was good back then, can't imagine it still isn't. Carb rebuild would be all she needed I'd think.

If you or any one else is interested I'll get you a SN and be sure the LU still holds pressure and there's good compression. Depending on where you are, the shipping may kill ya.

 

[tashasdaddy]

Re: 1968 20 hp wont crank out RPM's

i suggest you read the TOP SECRET FILE top of this forum, check your spark, and compression, and go from there.

 

["G"]

Re: 1968 20 hp wont crank out RPM's

i suggest you read the TOP SECRET FILE top of this forum, check your spark, and compression, and go from there.

HEY HEY... that is top secret info you're passing there! Before ya know it everyone will be doing it! (Wouldn't that be the day...)

 

[samo_ott]

Re: 1968 20 hp wont crank out RPM's

Check for spark. Sounds like it might be running on one cylinder.

Also they never made a 20hp with a pressure tank. It must have been the 18hp.