WOT issues
 

Hey guys new to the forum,

I bought an 88 223LS this spring with the 454 in it. I'm running the mirage plus 23P prop. Here is my issue. I'm running 4000RPM at about 50MPH(WOT). but after running the boat for a while it clears up and I come up to 45-4600RPM at about 60MPH. I will not touch the throttle at all, it will just open right up. Took a quick look under the hatch last night and notice the flame arrestor was pretty clogged up so I pulled it off cleaned it up with carb cleaner dried it and threw it back on. My problem still exists. took it out on the lake this morning and the same issue remains. Any clue what's going on? Almost seems like it is loading up on fuel then clears itself out for a bit and then loads up again. Any ideas would be great.

Thanks guys

This may be entirely off base... But are you trimming the boat? Most boats only get their last 4-500rpm's with the right trim setting.

Yup, trimmed out tabs up, just me in the boat. It's just so strange because its intermittent. The boat runs great when its not bogging down on me.

Change the fuel/water separator and any inline fuel filters you may have. Also check for a weak fuel line tank to fuel pump that may be collapsing.

How is the fuel quality?

Check the water separator.

I will check that out in the morning. Thanks guys. Fuel should be good. Just put in some fresh mid grade this morning.

so I replaced the fuel filters on it today(separator/Carb), problem is still there. Let the fuel that was in the separator settle out, no water in the fuel. any other ideas??

Could be a weak rubber fuel line that is collapsing under suction. something is restricting fuel delivery...you just have to sort out the reason.

Next time it does this immediately loosen the fuel cap....if you detect a rush of air you have a vacuum lock. Check the vent screen on the thru hull for obstruction.

Have you verified the choke is staying open?

Worn out plug wires have caused those symptoms for me in the past.

Try running a farily concentrated mixture of Seafoam through it.

ok I'll double check and do all you guys have suggested. Thanks for all the ideas guys, just love to get my boat running the way it should!!

Check the anti syphon valve in the fuel tank. I had the same issue with my old Baja. As mentioned before I would replace the fuel line from the tank to separator

I would look in a different direction. Usually if something is clogged or starving for air/fuel the engine will run OK then the RPM's will diminish. You have the opposite problem, it clears out after WOT. I would pull the plugs and see if there is fouling or traces of water from leaky manifolds.

Secondaries not opening? My friend had a similar problem with his SB with vaccum secondaries. The screws holding the link for the butterflys were loose.

This must be contagious...now mine is doing some thing similar....suddenly this afternoon neither engine (Twin 400+ HP Vortec SBC's) would spin over 3200 and previously today I had a few runs into the low 70's at about 5200 RPM. I'm going to follow some of my own advise!!!

Stay tuned...

You're kidding!! Well I made a bit of head way today. I pulled the plugs and re-gapped them today. I revved about 4400 at wot. I have a bit of a miss while puttering. I'm going to get all new plugs wires and cap soon. Double check the gap on the the before install. Then double check my timing and hopefully I'll be laughing!

My anti siphon tank connections are original as far as I know and being 35 years old and every thing else in the fuel/ignition system being new...that's the first place I'm looking. Cheap $15 part times 2...hell of it is I have to almost take the a$$ end of my cockpit apart to get to them. The devil is in the details for sure!!

did either of you come up with a reason for weirdness?

I just pulled and re-gapped my plugs. Runs like a top now. The gap was small so we figured not a long enough spark so it was loading up on fuel. Still has a slight miss at idle. New plugs wires rotor and cap in the spring should solve that.

get rid of the anti syphon valve

Fuel pressure gauge installed will let you know you have proper fuel delivery.