Sputter when I mash the throttle.

[tgell001]

I have a 2010 stingray with a 3.0L. Its got a carb believe it or not, even in 2010.

So anyways, this problem is new this summer and its not really a HUGE problem but when I'm towing a wakeboard it can be annoying. When I work my way onto the throttle from idle all the way to open it run like a champ but when I try to go from idle to 3/4 or so throttle i'd say 25% of the time itll sputter and you have to back off before it stalls.

I'm pretty mechanically inclined (I have an engineering degree) and I do all my own maintenence and repairs so I'm not a total idiot but only being 25 years old carbs were before my time. My first assumption is that the carb jet is dirty so I bought some cleaner. Is this a fair assumption? and if so whats the best was to use spray carb cleaner.

 

[hostage]

Re: Sputter when I mash the throttle.

Could it be the dist cap, I had something similar?

 

[tgell001]

Re: Sputter when I mash the throttle.

Good thought, easy fix to. I'll investigate and see if the contacts are dirty and just take some wd40 on a rag and clean the contacts and see if that helps. Anyone else have any theories? Preferably easy ones haha

 

[Fireman431]

Re: Sputter when I mash the throttle.

Sounds like accelerator pump to me.

 

[rbh]

Re: Sputter when I mash the throttle.

Good thought, easy fix to. I'll investigate and see if the contacts are dirty and just take some wd40 on a rag and clean the contacts and see if that helps. Anyone else have any theories? Preferably easy ones haha

I would replace both the cap and rotor if the contacts/posts are green and pitted, could be carbon tracking in the cap, could be a small crack, even just damp and dirty will send sparks everywhere?
How old are the plugs and wires?

 

[tgell001]

Re: Sputter when I mash the throttle.

I hope its not a mechinical problem in the first 100 hrs. But after reading about the accelerator pump it sounds like it is related to the problem i'm having.

 

[RogersJetboat454]

Re: Sputter when I mash the throttle.

Heres a silly question.... It being a 2010 and all, is this still under warranty?

 

[tgell001]

Re: Sputter when I mash the throttle.

Sure is but a trip to the shot will likely cost me two weekends off the water. If its a simple fix i'd gladly do it myself.

 

[Kaplooi]

Re: Sputter when I mash the throttle.

+1 on the accelerator pump being out of adjustment. Given that it's a 2010 I'm assuming you're using whatever was the factory setting which is either too rich or too lean. On my comparatively ancient 1989 4.3 4bbl there are 3 adjustment points on the rod to the accelerator pump that lets you control how much fuel is shot in when you open the throttle quickly. Given your background you'll understand the physics behind the problem. Basically the manifold vacuum rapidly falls off when you open the throttle suddenly so there's not enough of a venturi effect to draw enough fuel through the jets to match the amount of air that gets drawn in at that moment. The accelerator pump attempts to compensate for this transient event by injecting a metered shot of gasoline mechanically as opposed to relying on the venturi effect to draw more fuel through the jets. It sounds like a lean condition if you have to throttle back and let the carb catch up on fueling.

 

[tgell001]

Re: Sputter when I mash the throttle.

I read up on the theory after i got the first response about the accelerator pump. Now i just need to do some investigating to figure out how to adjust this. Haven't ever looked for this specifically so I can't picture it (probably because the view of this area is obstructed by the air filter). Anyone with a 3.0L out there that can give me some guidance?

Oh thanks for all the support, I would have been soaking my intake with carb cleaner with it. Saved me a head ache (litterally)

 

[Jeepster04]

Re: Sputter when I mash the throttle.

Far as I know you can't adjust an accelerer pump. It either works or doesn't. You can buy a rebuild kit for your carburator that should come with the accelerater pump.

When was the last time you changed the fuel filter? There should be a screen on where the fuel line hooks to the carb, may want to check that too.

 

[tgell001]

Re: Sputter when I mash the throttle.

I changed the fuel filter in april when i did all my preuse maintenence. Didnt check the screen because i figured that if i have something restricting fuel flow then it would do it at full throttle regardless. I saw another post in the Merc forum about there being a three holed lever on the linkage to the accelerator pump and you can move it between these three holes to add or removed CC's from the accelerator pump input. Does anyone have insight regarding this claim?

 

[Glastron175]

Re: Sputter when I mash the throttle.

I have the exact problem with my 2000 model 3.0L GS. I have put in two carb kits. The second one a Holley since I read that Sierra kits did not always fix the problem. Still have the problem after the Holley kit. Both kits included new accelerator pumps, so don't think that is the problem. Also it squirts two good streams of gas when moving the accelerator. Have adjusted the mixture screws as per manual. I read in the Holley forum (for cars) that the power valve should be 1/2 of the vacuum at idle. At idle I have 15 inches vacuum, so the power value would be a 7.5. It has a 3.5 which is what came in the renew kit. The old one was also a 3.5 though, so I wonder if that applies to marine as well as cars. Now I suspect maybe timing could be the culprit. But it runs fine at any speed if I just adjust the throttle slowly to get there. Wouldn't timing advance affect that also if it was off? Just about out of things to try. Let me know if you get yours working and how.
Thanks.

 

[Glastron175]

Re: Sputter when I mash the throttle.

I forgot to mention. I have also replaced the rotor and plug wires and plugs. I just noticed that someone suggested that to you. It did not help mine.

 

[YahooMarine]

Re: Sputter when I mash the throttle.

Hello. I have the same problem in my 2009 18" Chaparral with the Volvo 3.0 engine. The engine worked great in 2009, became hard to start last year and this year in addition to being hard to start it dies if I hit the thottle hard. Above 3000 rpm all is well, but below that it will die unless I back off until the engine catches up.

I have just over 30 hours on the engine. This problem developed over the winter as it did not do this when I took it to be winterized last October but did do it the first time out this April. The Fuel/water separator is new. Also, I bypased the separator and that did not fix the problem.

The selling point of this engine 2 years ago was a 7 year warranty but I still need to haul it 35 miles and lose it while it waits its turn for hopeful repair. My plan is to live with it until the fall. However, if anyone can tell me how to remedy this I'd love to do it.

One more thing... in February of 2010 the carb had a recall from Volvo for potentially improper assembly of the throttle plate. Some had loose screws that were ingested by the engine. Mine was removed and checked by a factory rep and possibly that is when something was put back incorrectly. This makes the accel pump seem more plausible as perhaps the arm is just in the wrong place. I shall look this weekend to see if there are more holes for this arm to go into.

Any advice will be appreciated.

Regards, Rich

 

[Glastron175]

Re: Sputter when I mash the throttle.

Just got mine off the water about two hours ago. Pulled a tube around at any speed I wanted with no problem. Just couldn't "goose" it without it stalling. On our 3.0L GS there are no holes for adjustment on the accelerator pump. I've seen that suggestion too on a Merc I/O forum, so apparently that is a different type carb. Ours are Holley 2 barrel carbs. Still looking for a solution. I am wondering about the timing advance. Have you checked to see if yours is advancing properly. I haven't the timing light required for that check.

 

[redneck_cdn]

Re: Sputter when I mash the throttle.

Have you Checked or replaced the fuel filters?
I have a 96 Four Winns Horizon 3.0GS/SX Cobra and had hesitations problems last season, checked, cleaned everything, replaced the filter in the base of the Holey Carb as well as the filter in the bottom of the engine mounted fuel pump this spring. I also added an inline fuel/water filter system to prevent any fuel contamination issues this season.

So far so good.

 

[Glastron175]

Re: Sputter when I mash the throttle.

I put a new filter in the carb, as it came in the rebuild kit. I just cleaned the filter in the fuel pump, although it was pretty clean to start with. I'm still wondering about either timing advance or the power valve being the wrong one. How much vacuum do you have at idle? Mine is about 15 inches.
Let us know if you find the solution. I'll do likewise.

 

[kendrive]

Re: Sputter when I mash the throttle.

I am having the same problem with a 2001 3.0 GS in a Larson 180 SEI. Has anyone figured out the solution?
I replaced the rotor, distributor cap, spark plugs and wires. I also rebuilt the carb and replaced the fuel filters. The hesitation is less, but still annoying. Is this a carb adjustment problem?

 

[insttech1]

Re: Sputter when I mash the throttle.

Everyone is rebuilding their carbs and putting in new diaphragm pumps (and in some cases getting strangely-sized power valves). However, are you also performing the adjustment on the pump arm with WOT on carb, and pump arm fully depressed? Clearance should be set with a feeler gauge to .015", I do believe, and also ensuring the carb float is adjusted correctly may help. (Mine was massively out of adjustment when opened.)

I had the same dead space/hesitation issue; I cleared 80% of the hesitation by ensuring that all carb adjustments were performed after rebuild; not just cleaning and new gaskets. I also found that my throttle control from the cable/linkage was not set correctly, and was actually screwing up my carb throttle response until I set it correctly with basically zero preload.