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220 bogs and loses power at wide open throttle.

Posted: Sat Mar 18, 2017 10:52 pm
by TDezso
Having a problem with my motor bogging and losing power at wot. It's a Holley 500 with 76 jets. It also seems to run rough around 2000rpm.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 2:24 am
by blackpowderscout
Is your fuel pump keeping up with the demand? Maybe an obstruction on the screen or in the lines somewhere?

Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 10:45 am
by TDezso
It's like to much fuel. My manual pump keeps up. I only use the electric to prime the system.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 10:49 am
by GMAC 76
check your points gap......and coil may be weak

Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 11:17 am
by Deano
GMAC 76 wrote:check your points gap......and coil may be weak
x2

Beyond that, the general consensus seems to be #74 jets . . .
http://southernairboat.com/phpBB3/search.php?keywords=%2B220+%2BHolley+%2B500+%2Bjets&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 11:42 am
by TDezso
Researching it, I could have a wrong size power valve. I'm going to check vacuum and see what size valve I need and order it and some #74 just. Just to start with a fresh setup that I know is right for my engine.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 12:21 pm
by Deano
Sounds like the prudent thing to do, and a safe bet to me.

I always like adding to the "Well, I know it's not that" list. :)

Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 2:43 pm
by Swamp Thang
I had a very similar issue recently with my GPU, disconnected the fuel line between the electric pump and the mechanical pump to check the pressure coming out of the elec. pump and there was almost no pressure.... so off to the auto parts store I go with receipt in hand for a warranty exchange, get back home and install the new one. Hit the fuel pump switch with the fuel line in the clear bottle before I hook it back up and still almost no flow... WTF? :scratch: :scratch: scratch my head a couple of times and start checking the lines & fittings back to the fuel tank, didn't take long to track it down. Ended up being a little corrosion on the spring in the check valve fitting at the top of the tank, removed the ball & spring....Problem solved :D

Re: 220 bogs and loses power at wide open throttle.

Posted: Sun Mar 19, 2017 3:05 pm
by TDezso
Swamp Thang wrote:I had a very similar issue recently with my GPU, disconnected the fuel line between the electric pump and the mechanical pump to check the pressure coming out of the elec. pump and there was almost no pressure.... so off to the auto parts store I go with receipt in hand for a warranty exchange, get back home and install the new one. Hit the fuel pump switch with the fuel line in the clear bottle before I hook it back up and still almost no flow... WTF? :scratch: :scratch: scratch my head a couple of times and start checking the lines & fittings back to the fuel tank, didn't take long to track it down. Ended up being a little corrosion on the spring in the check valve fitting at the top of the tank, removed the ball & spring....Problem solved :D


I chased that same problem when I first got the boat. The pick up tube was to close to the bottom of the tank and would starve the engine. This problem I never lose pressure on the gauge.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 1:38 pm
by John Fenner
Pull fuel inlet adapter off the bowl, remove sintered bronze filter and spring and throw them away. If none present then be sure of tank vent clear of debris, also depending on electric pump type, it may or may not allow full free flow when off, and it may have a screen that is clogged.

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 1:42 pm
by TDezso
I don't lose fuel pressure. The gauge stays at 5-6psi the whole time. It's like it is flooding out and clears up when I get off throttle.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 3:43 pm
by John Fenner
Is the gauge in the bowl, post sintered filter? Nope.

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 4:10 pm
by Deano
Have you run it, bogged it out and shut it down in one motion, and then read the plugs? Doing so should confirm or deny your flooding theory. It sounds like, and odds would seem better it isn't getting enough gas.
Are you sure the float level is set correctly? Sure your gauge is accurate?

Holleys are designed to run with 7 psi. I have a buddy that had a 350 w/650 Holley that argued his 5 1/2 lbs disallowed for any fuel pump issues. After trying everything else (to include a carb), he finally replaced the pump, got 7 lbs and that was the end of his problem. You have more cubic inches than he did.

Pressure really doesn't mean anything if you don't have volume to go with it. Do you have sufficiently sized fuel line that's in good shape? If the inside of an old line is collapsing, it will not pass the required volume.

I would first do what John suggested and then use no filter(s), one pump, good line and pull it from half a five gallon can. If it runs OK like that, you can add things back one at a time until you have the problem. If not, try the other pump.

I had one that acted like that and it ended up being the filter in the tank was crapped up. Now I start there and disallow for that first.

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 6:38 pm
by TDezso
John Fenner wrote:Is the gauge in the bowl, post sintered filter? Nope.

Gauge is last thing before the bowl.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 7:00 pm
by TDezso
Deano wrote:Have you run it, bogged it out and shut it down in one motion, and then read the plugs? Doing so should confirm or deny your flooding theory. It sounds like, and odds would seem better it isn't getting enough gas.
Are you sure the float level is set correctly? Sure your gauge is accurate?

Holleys are designed to run with 7 psi. I have a buddy that had a 350 w/650 Holley that argued his 5 1/2 lbs disallowed for any fuel pump issues. After trying everything else (to include a carb), he finally replaced the pump, got 7 lbs and that was the end of his problem. You have more cubic inches than he did.

Pressure really doesn't mean anything if you don't have volume to go with it. Do you have sufficiently sized fuel line that's in good shape? If the inside of an old line is collapsing, it will not pass the required volume.

I would first do what John suggested and then use no filter(s), one pump, good line and pull it from half a five gallon can. If it runs OK like that, you can add things back one at a time until you have the problem. If not, try the other pump.

I had one that acted like that and it ended up being the filter in the tank was crapped up. Now I start there and disallow for that first.


I haven't had a chance to get it out to get it to bog and pull the plugs. All fuel lines are new and 3/8" and I have no filter in the tank. I am only at 5.5psi with one or both pumps. The manual pump is a Plymouth pump that people were running on here and the electric is a solid state pump of some kind. I do not know the brand. It's run from tank, electric, filter, manual, gauge, then carb. Also fuel bowl level is set just below sight plug sitting level.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 7:06 pm
by glades cat
6.5 power valve.

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 7:14 pm
by TDezso
glades cat wrote:6.5 power valve.

I believe it is a 6.5 valve that was in the rebuild kit. Going by what Holley says to select the correct valve I should be running an 8.5. I have 19in of vacuum at idle when warm. Is it different for aircraft engines? I also read people are putting block off valves in.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 7:20 pm
by TDezso
Might be a 4.5. Also it bogs if I stab the throttle from idle.


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 8:08 pm
by peanutbutter kid
i've had the electric pump clog up when u don't have a filter between the tank and pump .. on my gpu i run tank, water separator, manual pump, another filter and to 500 holley....

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 8:13 pm
by TDezso
What's a good pump on a budget? I see carters around $60. What model?


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Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 8:59 pm
by diamondback0320
i used to swear by carter pumps until year b4 last...mine took a dump after who knows how many years it was on this boat..replaced with a new 1 & it didn't last 6mthns.. talked to a few mechanics & was told carters are being made overseas now just like everything else..ended up buying the gold series facet & has been on the boat bout a year with no problems whatsoever

Re: 220 bogs and loses power at wide open throttle.

Posted: Mon Mar 20, 2017 9:25 pm
by TDezso
diamondback0320 wrote:i used to swear by carter pumps until year b4 last...mine took a dump after who knows how many years it was on this boat..replaced with a new 1 & it didn't last 6mthns.. talked to a few mechanics & was told carters are being made overseas now just like everything else..ended up buying the gold series facet & has been on the boat bout a year with no problems whatsoever


What model facet did you go with?


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Re: 220 bogs and loses power at wide open throttle.

Posted: Tue Mar 21, 2017 12:28 am
by diamondback0320
not sure what part# it is I'll look in the morning

Re: 220 bogs and loses power at wide open throttle.

Posted: Tue Mar 21, 2017 10:12 am
by diamondback0320
facet 40007 is the 1 i bought for my lycoming

Re: 220 bogs and loses power at wide open throttle.

Posted: Tue Mar 21, 2017 10:17 am
by TDezso
diamondback0320 wrote:facet 40007 is the 1 i bought for my lycoming


What does it run for pressure? Says max is 5.5psi


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