symptoms of needing to decarb?

[ncbassfisher]

Can someone help me please.
A couple of months ago my 200hp ox66 started running a little funny at WOT is would act like it was running out of gas kind of surging or lagging a little. It has progressively gotten worse yesterday it was so bad i could hardly get up on plane. The thing cranks right up with a bump of the key and idles around fine. I have replaced all fuel lines, changed little fuel filter(the one in the clear canister), checked vent hose, replaced anti siphon valve at fuel tank with a nipple, replaced 3 low pressure pumps. I also cleaned oxygen sensor. Are these symptoms related at all to needing to decarb? I need help, all the shops around here are very busy and i don;t want to be without boat for a month!!!!

Thanks for any help

[Stratos21XL]

have you checked or changed the spark plugs lately? What about the primer bulb, did you pump it and hold it to see if it stays firm?

[Rich Z]

Inspect the plugs and change them if any look abnormally dark. Do a compression test. All cylinders should read around 115psi. Compression numbers can be higher if there is a lot of carbon build up on pistons and heads so a decarb is needed. Hook up a hose to the flusher connector but don’ crank the engine. Inspect the area where the ecu is mounted and look for water behind the ecu. If water is visible then the gasket on the exhaust water jacket needs to be changed. The water will eventually get on the ecu harness plugs and can cause all sort of problems. This does however sound like a plug or an o2 sensor problem. Have you installed a new gasket on the new o2 sensor? Also, have the injectors ever been cleaned and flow tested?

[ncbassfisher]

Yes the plugs have been changed the old ones looked but i changed anyway. The primer bulb will stay firm all day unless i'm running the motor, then it will get soft. I was told the bulb will not stay firm while the engine is running is that correct? What about after shutting down should the bulb still be firm? Mine does stay a little soft after running motor but the thing cranks back up just fine.

[ncbassfisher]

When I checked and cleaned the O2 sensors I didn't have a new gasket but the old one seemed in really good shape. The sensor and the little tube were pretty carbed up I cleaned them up the best i could. I just figured if they were that junked up maybe the cylinders were the same. I'll do a compression test tomorrow.

[ncbassfisher]

Heres another question pertaining to the fuel bulb. The other day I had the fuel lines disconnected. When I reconnected them I pumped the bulb a few times but it seemed like the bulb was just full of air but it was firm. So I disconnected the line from the bulb to the motor and pumped in until gas started to come out however it kind of just spews out like there is some air still in there instead of squirting out like i thought it should. When the bulb is soft, its soft because theres no or little fuel an or some air in there. Where does the air get blead out to while pumping the bulb. Is there some kind of air relief valve? I forgot to mention I installed a yamaha 10 micron 90 gpm fuel filter/water separator a couple months ago my problems started at or shortly afterwards. I have tried bypassing the filter but the problem is the same. Could there just be some air locked in the line?

[Rich Z]

To purge all the air out from primer bulb you need to put your finger over the end of the fuel line after you squeeze the bulb. Repeat several times and then connect the line to the clear filter on the motor. Retighten all the hose claps and ensure the bulb directional arrow is pointing up or at the very least is horizontal. I would still check for water behind the ecu and install a new gasket on o2 sensor.

[Stratos21XL]

Air in the line mixing with fuel will definitely cause poor performance. I would go over all of your connections and make sure they are air tight.

[ncbassfisher]

Thanks guys for the tips