4a084 trouble

**swampdoo** · 12-10-2010, 07:51 PM

So i just got me a airboat last friday took it out for the first time and it idle great but when i went to give it throttle it ran high rpm for about three minutes then started bogging down so i let off the throttle it went back to idle it does this every time i give it throtlle will run fine for a few minutes then bog down. It has a new carb on it
I put an elec fuel pump on it thinking the mechanical one was bad but it still does the same thing does anyone have any ideas?

**Papee** · 12-10-2010, 08:52 PM

What carb is on it?

What rpm are you at when it bogs down?

How long are you running at that rpm before it acts up?

**dwhittaker** · 12-10-2010, 09:00 PM

what CARB do you have on your 084. I have had some problems with carb icing with My 084 . But with only 2 hours on mine I dont have much for answers. Carb icing has been coverd in earler post. I have the solex carb on mine. GOOD LUCK!! dwhittaker

**swampdoo** · 12-10-2010, 09:03 PM

its the one from saturn supply the guy i got it from had changed it last wednesday before i got the boat i have done everything i know the float is good, it will run for about 2 minutes at max rpm

**buster** · 12-10-2010, 09:49 PM

I think I had a problem with carb icing and mine would act similiar. The only thing I did was to switch to a better grade of gas, one without ethynol. I understand ethynol will actually increase the chance of carb icing.

Good luck with that,
Dave

**swampdoo** · 12-11-2010, 07:29 AM

so what yall are saying is that im having a carb icing problem??

**swampdoo** · 12-11-2010, 08:24 AM

Also sometimes when i let off the throttle it will backfire through the carb

**n4wsp** · 12-11-2010, 11:22 AM

Make sure your gas tank vent is open

**swampdoo** · 12-11-2010, 11:36 AM

n4wsp, that was the first thing i checked i ran it without the cap on and it still does it

**n4wsp** · 12-11-2010, 04:06 PM

This setup is how i fixed my carb iceing problem.

Steve Name: carb ice.JPG
Views: 1058
Size: 15.3 KB

**swampdoo** · 12-11-2010, 04:25 PM

I have a setup very similar to that and it does the samething with or without an airfilter on it how do i know if it is icing i know there was alot of condensation on the carb

**swampdoo** · 12-11-2010, 04:26 PM

Also is the crankcase breather tied into the intake??

**Duane Scarborough** · 12-11-2010, 06:37 PM

swampdoo,

Welcome to the forum.

From what you've described, you MAY have a carb icing problem, but I'm not so sure.

You said that it idled O.K., then after about 3 minutes of high RPM running, it would bog down.

That MAY be carb icing... but I'm still not so sure. It sounds more like a fuel starvation problem.

Does it idle O.K. after this happens?

If the carb has iced, its probably not going to idle very well, or at all afterwards.

What was the air temp and humidity when this happened?

Ironically, carb icing (at sea level altitude) is more likely to occur in warm temp, high humidity, after running at a high throttle for an extended time, and then going to a low throttle.

Reducing the throttle even more after an icing incident generally makes the engine run worst, not better.

BTW, where are you located?

Thanks,

Duane

**swampdoo** · 12-11-2010, 06:50 PM

Duane
Yes it does idle fine sometimes after it bogs down it will stop running and sometimes it will catch itself after backfiring i think the temp was around 45-50 and hum at 98% , Now after it bogs down it sounds like it is missfiring but it will eventually catch itself

**Duane Scarborough** · 12-11-2010, 07:21 PM

swampdoo,

Well, at that temp, and humidity, and those symptoms, it does begin to sound more like it may be a carb icing problem.

I'm not sure what to suggest. The aviation guys use carb heat to get around this.

If you google carb heat, you'll see how they do it.

You could try jury rigging up something to use your exhaust heat to prewarm your intake air temp. If that fixes it, than you can go for a more permanent solution.

Other than that, I'm kinda' stumped.

Duane

**swampdoo** · 12-11-2010, 07:28 PM

thats what everybody is sayin im a mechanic by the way and its whiping me

**swampdoo** · 12-11-2010, 07:32 PM

its getting really aggrevated i am really discouraged with this dang engine wish i could find a solution

**chuckitt** · 12-12-2010, 08:28 AM

Hey swampdoo, take about a 2 inch long pcs of 1.5 inch tube and tack weld it to the side of one of your header tubes where air can come in around each side of your header tube and run a hose from it to your carb inlet. The warm air flowing over the header tube should stop carb iceing.
Thanks, Chuck