Poor Bottom End

[jamesroger]

I own a 2003 Outback DD with the Carb engine. When we first bought the boat we were a little dissapopinted about the whole shot, loaded with people and even with just myself in the boat. We started doing small changes to the boat to see if we could fix the problem but no such luck. In an attempt to improve the bottom end we have replaced the fuel filter, distributor cap and rotor, spark plugs, prop, and have ran numerous bottles of fuel additives through the engine.

Once the boat hits about 2600 RPM it takes off and really wants to go, how it should be, responsive on the throttle and runs good.

My question is are there any other 'things' that could be causing this problem?

Thanks for any help!

[kaneboats]

What prop are you running? What speed at 2000, 3000 RPM and what speed and RPM at WOT?

[AaronWhitt82]

I own a 2003 Outback DD with the Carb engine. When we first bought the boat we were a little dissapopinted about the whole shot, loaded with people and even with just myself in the boat. We started doing small changes to the boat to see if we could fix the problem but no such luck. In an attempt to improve the bottom end we have replaced the fuel filter, distributor cap and rotor, spark plugs, prop, and have ran numerous bottles of fuel additives through the engine.

Once the boat hits about 2600 RPM it takes off and really wants to go, how it should be, responsive on the throttle and runs good.

My question is are there any other 'things' that could be causing this problem?

Thanks for any help!

Has the carb ever been rebuilt? If not, it is probably a good time to do it. It is possible that it might be all gummed up inside.
Does the boat stall at all or just seem like a lack of power?
What size prop are you running?
I would start by checking the float levels, make sure the accelerator pump is adjusted corrrectly and check the fuel filters at the fuel bowls. (You have to disconnect the fuel line at the carb and then remove the fuel fittings and there is a screen or a small filter in the fitting.)
I would also pull a spark plug and see what the color looks like to see how the motor is running.
I would stay away from using fuel additives with alcohol because that will just cause more problems. The only thing I would use is Stabil & Seafoam.

Check out these links for other things to check:

http://forums.iboats.com/showthread.php?t=295070

http://forums.iboats.com/showthread.php?t=283269

[h2oskierrick]

If you have a holley carb there is a good chance you have a blown power valve. When the diaphragm on the power valve ruptures it causes raw fuel to dump into the carb and it will bog down until the engine RPMs catche up.

Some symptoms are poor low end performance, rough idle, extremely rich at idle, and the faster you go the better the engine runs. It only takes a slight backfire to rupture the power valve.

Easy fix though. remove the front bowl and metering block, remove and replace!

[jjerrod]

This is my exact problem as well with my 02 outback DD. I also have a carb engine with all the same symptoms. Out of the hole it bogs down then when the engin rpms climb it really takes off. Is this the correct power valve?
http://www.skidim.com/prodinfo.asp?number=HOL125-25

[AaronWhitt82]

Yes, correct power valve is a 2.5 if you have the Holley 4150 PN 75021-1

[jamesroger]

Thanks for all the replies!

So last week finally got the carb rebuilt... put it back in and no better. Went around and checked all the float levels in the bowls adjusted the idle new spark plugs reset the metering screws changed the oil but still no better. So we assumed could just be another blown power valve because screwed both metering screws in and did not stall. So once again ordered a new power valve, put it in and ran the boat again; still no better; the same symptoms... would screw metering screws all the way in and engine would not die?!?

When we hammer on the throttle it seems to jump up to 2300 rpm and just sit there until the boat planes out and then will eventualy start climbing and the boat will take off. At WOT the rpm is just over 4000 and the top speed is 42mph.

Any more suggestions out there? Boat is causing more greif then joy this summer and summer's just about gone!!

Boat is a 2003 Outback DD with the 5.7L Carb engine

[zabooda]

What is your prop size?

[jamesroger]

prop is a ACME 13 x 12 (.080 c) 3 BLD, 1" Bore, LH

It did the same thing with the stock prop so thought changing it would help but no such luck

[AaronWhitt82]

Thanks for all the replies!

So last week finally got the carb rebuilt... put it back in and no better. Went around and checked all the float levels in the bowls adjusted the idle new spark plugs reset the metering screws changed the oil but still no better. So we assumed could just be another blown power valve because screwed both metering screws in and did not stall. So once again ordered a new power valve, put it in and ran the boat again; still no better; the same symptoms... would screw metering screws all the way in and engine would not die?!?

When we hammer on the throttle it seems to jump up to 2300 rpm and just sit there until the boat planes out and then will eventualy start climbing and the boat will take off. At WOT the rpm is just over 4000 and the top speed is 42mph.

Any more suggestions out there? Boat is causing more greif then joy this summer and summer's just about gone!!

Boat is a 2003 Outback DD with the 5.7L Carb engine


That is usually a sign of a bad power valve when you screw the air/idle mix screws all the way in and the boat does not die.
Another thing I would check is the secondary speed screw which is on the bottom of the carb near the secondary diaphram. You want to adjust that to where it just touches and cracks the throttle blades open and yours might be out of adjustment which if the secondaries are open too much it could cause the same symptoms of a bad power valve I believe.

http://www.youtube.com/watch?v=__3ruSX8Q_A

[jamesroger]

Thanks for all the help and ideas's!

Went out this weekend and tore the carb off again to adjust the secondary speed screw. When i adjusted it it reved up the engine at idle but still when i would hammer on it it would climb to 2300rpm and would sit there for a few seconds...long seconds, and then would continue to climb after the boat got on plane.

Once the boat has passed the 'magical' 2300-2400prm mark it takes off and runs how it should, just that initial whole shot when it is boggy is really getting to me.

Any more idea's out there I could try? Maybe might not be a carb problem?

Am still a little worried because screwed the air/fuel mixture screws in and would seem to make the boat run smoother, not choke it out how it should; Already on the third power valve!!

[vk_boomer]

Did you turn both air mixture screws all the way in and back them out 1 and half turns, then adjust each evenly. When you adjust each screw in, and the rpms do not die down, this is a good sign of a vacuum leak. I would check all of you rubber hose. Maybe this will help, just my 2 cents......

[jamesroger]

Yes i have turned them both all the way in then backed them out the one and a half turns as a starting position. When turning the mixture screws I should be seeing a rise in rpm's but no matter how many turns in either direction they do nothing.

Which hoses do you mean i could be loosing vacuum through? there are only two hoses that come off the carb; one form the flame arestor going to the passenger side and another going to the driver side just beind the oil fill cap. Are these the ones you are refering to as could be leaking?

[jamesroger]

Just an update incase anyone else may be having the same problem...

After rebuilding the carb, changing filters, changing a prop; the problem boiled down to a timing issue. We took it to Matrix Marine in Leduc Alberta, really awesome guys by the way, and they re-set the timing and now it runs like a top. Our rpm's at WOT jumped from 4000 to 4800 and the top speed increased by about 6mph.

All in all was an expensive lesson in carb's that boiled down to a simple problem. Thanks for all the feed back!


James