motor issues, carbs dirty maybe?

[2182]

so i repowered a few years ago w/ a carbed 150 johnson on my 18 seacraft. had an old mercury 200 racing motor that ran like a scalded dog, but not very often. anyway, went out monday to go catch some breeder reds. ran ten miles, fished for a few hours, and on the way in i started losing power. motor bogged down at about 4000 rpm and would slowly lose power (bucking). i stopped, put it in neutral, let it idle for a few, and started again. got 1/4 mile or so, same deal. repeat, but just barely got her on plane, and went a bit farther before it happened again. this time was accompanied by loud warning beep and "check engine light", which means fuel flow restriction. this happened once before last time i was out (the previous monday), but just once, and i forgot about it. i change plugs and fuel/water separators every six months, but i think it may be time to clean the carbs. is that what this sounds like? would love to tackle it myself, but would love to get some insight first. im no master mechanic, but i can turn a wrench and dont mind getting dirty.

as for gas, i try to run ethanol free, but dont always. use bright blue startron religiously though...

[Daltonmarineinc]

before going after carbsi would try and run it on a differnt fuel tank. this will sperate the problem,boat or motor. if it runs fine then try finding your fuel pick up in the tank.alot of times theres a screen that gets cloged up at the bottom.also check and see if there is a check valve at the tank its self. if it is the motor then yes, i would take the carbs off and clean them. make sure and buy kits before taking them off.the oring and gaskets will swell and will never go back together. good luck!

[BigLew]

I'll bet you have water accummulation in the float bowls. take them off and dump them and clean them out. It is probably from water seperation from the gas and it has taken up most of the volume of the bowls, thus limiting the amount of burnable fuel reaching the motor.

Just my 2C. Good luck.

[fredetzel]

check the anti-siphon valve I had the same problem a few years back and found some trash in the anti-siphon valve it is mounted to the top rear end of the tank where the fuel line connects to the tank. Also check all fuel filters and check fuel lines to make sure the new ethanol gas hasn't struck again.

[2182]

pulled apart one of the carbs pre-knowledge tonight (very carefully). they were clean as a whistle. factory clean looking. cleaned it anyway, then pulled brass screws in stack and sprayed cleaner in there too. checked fuel filter on front of fuel pump and that is clean too. i have already checked fuel pick up and the anti syphon valve has already been removed. im at a loss. might be another bad vacuum switch, i heard they made a bad batch from my mechanic, maybe the good folks at omc were kind enough to send me a bunk replacement the first time. not sure how that explains the loss of power, although it would explain the godawful beeping. i have an inline filter for fuel management (which i dont use) that i may remove and see if that does it. blew off work to catch fish monday, and now im paying for it w/ a crazy week. going to try and water test thursday maybe, any more insight prior to that would be much appreciated.

[Caymanboy]

Hmmmm, maybe overheating?

[Yz2009]

If you got a continuous warning tone and not beeping it could be the overheat alarm. Have you changed your water pump recently?

[Bushwacker]

Definitely sounds like fuel starvation. When you let it idle for a few minutes, the pump refilled the float bowls, so you were able to get on plane until the fuel level in the bowls dropped. Hope you're not running premix (oil in the gas) instead of oil injection, because when you starve a pre-mix motor of gas, you're also starving it of oil! Have you checked the fuel lines between the pump and carbs? I had one of those lines deteriorate and plug one time on my old V-4. Could also be a weak fuel pump or a leak in the line to the crankcase that feeds the pulsations that drive the fuel pump!

[castalot]

How old is the gas mine did almost the same thing when I got it it ran good on a portable tank but not the main drained the 80 gallons it came with refueled and it's been good

[McGillicuddy]

Several good points made. I think Daltonmarine offers a good starting point. I'd start at the beginning of the fuel chain supply chain. Are you running off the main tank or auxiliary portable? Injecting oil or premix?

Assuming the primer bulb is still fully pliable, does it collapse at all when it cuts out? If so, that would likely indicate clogging between the tank and the primer bulb...or even a clogged or closed tank vent.
Here's what I found once that gave the same symptoms (my guess on this is that at some time silicone was used as gasket for sending unit which broke down and sunk to the bottom of tank) obviously no screen on my pick up tube:


Then check for water in the separation filter. Might just suck some fuel out into a clear container prior to the separator and see how it settles out...

No clogs, no water - work your way up to the fuel pump, fuel lines, then on to carbs... Bushwacker's logic makes a lot of sense if the problem isn't prior to the carbs.

Good luck, keep us posted