1990 aq 271 bogs and acts gas starved after hrs of run

[willscarver]

Ran 50 minutes at 3200 rpm out of the bay slowed and idled ran fine shut it down. Fired it up for the return trip ran fine for 10 minutes at 3200 rpm then started to bog and drop rpms but not stall then pull it self back up to 3200 then repeat again. Ran back at reduced rpm very slow. Back on land in the drive way ran fine.On another trip 20 minutes at 3200 rpm ran fine shut it down had lunch and a swim.Under way at 3200 rpm after 10 minutes started to bog. On each trip I filled up but ended below half a tank. I also disconnected my speed limitor the second trip.Made no differance.Runs fine in the drive way.

 

[Maclin]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

I am thinking the fuel supply is not keeping up with the carb's demands, or water in the fuel.

I would check fuel tank venting, if it is clogged then the fuel pump will eventually not be able to pull in fuel and become vacuum locked. That condition eases after a time. When on the water and this happens try loosening or removing the gas cap to see if that helps. Listen for hissing as you unscrew or unlatch the cap.

I would also check/replace the water separating fuel filter by pouring the contents into a glass jar, lookig at fuel quality and/or water content and general crud. I would replace the filter and not put the old one back on so have one ready if you do that.

There is a clear (or yellowing) hose that goes from the fuel pump's housing to the flame arrestor, about 3/16 inside diameter. This should not have fuel in it. if it does then the fuel pumps diaphragm has ruptured and sending fuel up that tube. That is the reason for the tube, to act as an indicator that the fuel pump needs replacing.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

Thanks I will get on it in the morning.I did not consider the vent.I have had a vent problem with a motorcycle in the past and should have thought of that. Gota check for water as I did fill at a different gas station and that is when it all started.Thanks again.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

The tube is clear.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

I have now checked and replaced fuel filter contents, were clear. Blew out the vent hose with compressed air, clear. Blew compressed air in fuel line and could here bubbles in gas tank. Replaced coil. Saturday Topped off tank ran down 1/4 out and back no problem. sunday ran down to just above 1/4 emty and started to bog. I think its not the carb it runs to well in a full rpm range. My list is getting shorter. Water in the gas, fuel anti siphon, a complete ingnition fault trace. Thought I nailed it with the coil ! Help !

 

[Maclin]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

So if you put more fuel in does it start running good again? If so I would suspect yor fuel gauge is not accurate, or the pickup in the tank is clogged and higher fuel level can get drawn in but not the last few dregs.

Water would be in the bottom of the tank, so if you had a lot of water then I think you would have differernt symptoms.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

Yea water is crossed off my list. Now my aluminum tank sticks out in the engine bay and the brass fixture threads into the tank. If unscrewed will gas flow out and is anti-siphon or anything I'm after on it. The fuel gauge is accurate because the gal. of fuel I put in is equal to 60 gal. capacity minus the 1/4 thats left in there. Thanks !

 

[Scott Danforth]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

all boats run fine in the drive way - there is no load on the engine

Just a few things to check:
when its starting to bog, do you get a backfire at all? pop, then RPM drop then recover, and repeat?
how are the two fuel filters at the carb? one on the inlet of each bowl
have you pulled the bowl sight plugs and checked fuel level - you could have a bad float

 

[Don S]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

Next time it starts to bog down, remove the fuel fill cap and see if things pick back up.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

Runs fine full rpm range on the way out,3200 rpm pull it down to idle and even trolled at 1000 rpm, shut down ate lunch fired it up on plane crossed the bay 3200 rpm shut it down for two hours. Fired her up hit 3200 rpm for 15 min began to bog. It was like flooding or miss fire had to pull back to idle and then it will take throttle but only for a short time and then start to bog. Did not stall or back fire but will not run well above say 1300 rpm. Pulled in to the cove no wake zone 1000 rpm ran well and will take throttle at the ramp.Back home in the drive way runs great.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

I allready checked fuel vent.You can check some of the stuff I did earlier in the tread.Thanks!

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

fuel sights are large brass flat head screws ? what should I be looking for ? are they level plugs?

 

[Scott Danforth]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

yes - large flat screw on sides of fuel bowls.

fuel level should be just to the bottom edge of the fuel sites

while you are working on the carb, I would recommend changing the fuel filters in the bowl inlets too.

 

[willscarver]

Re: 1990 aq 271 bogs and acts gas starved after hrs of run

Already did the filters. I will check the float level next.thanks for the tip.