1990 OMC spuratic running problems

"My boat is a 1990 seaswirl sp

"My boat is a 1990 seaswirl spyder sport 20' with ford 302.
Here is my problem. Boat will run fine tops out around 4k rpm at 43mph then occastionaly boat will drop down to 2500 rpm while throttle is still wot. Sometimes this issue will clear and back to boating as usual. Sometimes this issue will reduce boats performance to bairly idling with some popping/backfires/missing. While all of this issues are present you can shift boat into neutral and runs smooth as ever all the way to wot.

i have emptied gas tank and replaced fuel filter. Mechanic who really seems to know his stuff insisted it was carb, paid to have it rebuilt, still had problems and mech said stuff was getting by fuel seperator so we added in line fuel filter after water seperator and still having problems. Boat does shift in and out of gear pretty efortlessly so i do believe the shift assist is working. Also had shift cable replaced when clutch dog was done by same mechanic. This problem did exist prior to clutch dog replacement. Mechanic said antisyphon is fine. Should i be running high octane, fuel additive? What about fuel pump malfunction/detoriation of gaskets/diaphrams? any relay/choke that could be causing this?
Believe boat had plugs, wires, and cap in 2006

Thanks Guys!"

"David,I really dont have any

"David,I really dont have any advice but I am having the same exact problems except mine wont go over 30 at 3000rpm.I have a 19'6 Sunbird with a 302 OMC also.Hopefully one of us can get this whole mess figured out,so we can enjoy whats left of this short boating season."

Try going for a test run with

Try going for a test run with the ESA unplugged.

thanks Hy Stat! will give it a

thanks Hy Stat! will give it a shot today and post the results.

-dave

"Hy Stat

Tried unpluging t

"Hy Stat

Tried unpluging the esa with no luck. Still looses power. If you pump the throttle when it looses power it sometimes restores power. I am thinking fuel, pick up, antisyphon, fuel pump? Is the fuel pick up welded in place? How can you pull that up?"

"You could try hooking up a sm

"You could try hooking up a small portable tank with fresh gas to eliminate most of those things (except pump). Also check the fresh air vent for the tank, make sure it's not kinked or plugged.

The pickup tube is generally attached to the antisyphon which unscrews from the tank. On mine it's just a plastic tube that pops out of the AS."

"I will check that antisyphon/

"I will check that antisyphon/pick up. I imagine i will just to make sure that the antisiphon opens and closes relatively easy. and check for any noticable cracks, build up or wear?

The gas tank idea is a good one, probably need more time to aquire that stuff.

Thanks a bunch Bob!"

"i have a 1986 omc 4.3 cobra ,

"i have a 1986 omc 4.3 cobra ,when it warms up it .hesitates and doesnt run right have changed plug wires,plugs ,points ,cap and coil,still the same, timming is good ,rebuilt carburator but still ,does not run good ,i have found that there is gas, in the oil. any help would be much appreciated thankyou"

Ran the boat the last three da

Ran the boat the last three days and two of the last 3 days ran like a champ no problems! So frustrating. i guess the only good thing about my problem is i usually can get it to clear by pumping the throttle back and fourth.