only getting 4000rpm at wot

Hi I have a 1974 19 foot manatee boat with a 1988 100hp merc that I just bought. The engine has been retrofited from oil injection when i bought it, the engine would not idle so i took it to a marina and they cleaned the carbs and said it had the wrong plugs in it, they said they took it out on the lake and ran great, so I payed $350 and brought it home. I ran it at home and it ran great so the next weekend we took to the lake, the boat runs great at lower rpm but at WOT I can only get about 4000 rpms out of it so i thought that maybe it just needed cleaned out so we rode around for awhile and same thing then on the way back the the boat ramp running at WOT it was like a flip of a switch and jumped to about 5500rpm then died it ran out of gas, refueled tryed it again same thing 4000rpm I can disconnect the fuel line and it will jump up again seems to be running rich and once you lean it out it runs between 5-5500 rpm any ideas?

Re: only getting 4000rpm at wot

twilliams2552 said:

then died it ran out of gas, refueled tryed it again same thing 4000rpm I can disconnect the fuel line and it will jump up again seems to be running rich and once you lean it out it runs between 5-5500 rpm any ideas?

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I don't understand this part. Did you change tanks? Sorry, re-explain a disconnect of the fuel line and a jump up? How are you leaning it out?
We all here want to help, but your post is difficult to understand, for me at least

Re: only getting 4000rpm at wot

if i am running at wot 4000rpm and disconnect the fuel line from engine it will run 5-5500rpm until it runs the fuel out of the carbs thanks