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Old 11-08-2015, 02:35 PM
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Boat: 1990 Mastercraft Prostar 190
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Another Carb Problem, not one I've seen before, need help

Hey All - Having some issues with my new Edelbrock Carb. My Holley developed a large crack somehow (never heard of that) and was leaking fuel, decided to try the edelbrock as a replacement. I had a local marine mechanic do the installation, but I have a problem right away that I need help identifying the possible causes. Boat is 1990 prostar 190 with ford 351 indmar.

Here is the problem. I have to pump the hell out of the throttle to get it to start, Im talking 20 full pumps or more. Old one took 2 or 3 pumps. The second problem is this, if I leave it idling for a few minutes, even when warm, it will slowly start to drop rpms and eventually die.

I have already adjusted the idle mix screws and the choke and they are both good. The thing is, once its up and running, it runs great! My ski runs are flawless, power is good, no bogging. Idle is set at about 800 and drops to 650 when put in gear.

Its' acting like fuel won't stay in the bowl, like the jets are giving it what it needs to run well, but won't stay in bowl, like it's impossible to flood it.

If this were a fuel pump problem, bad gas, throttle problem, Why does is run so well during ski runs? why is there only a problem when starting or during a long idle?

If any carb guys have seen this before, Id love to know about it so I have something to suspect when I call and complain to the mechanic. Could it have been installed poorly?

Thanks as always - Scott
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Old 11-08-2015, 07:10 PM
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a spoon-shaped eating utensil with short tines at the tip

Last edited by Spork; 11-16-2015 at 10:45 AM.
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Old 11-08-2015, 10:46 PM
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Thanks James - yes, it's the 600 cfm. I will for sure look into those suggestions. I don't think I'm flooding it based on my throttle input, Ive had the boat for 15 years with 2 other carbs and it started up after 2 or 3 pumps every time, never flooding. It will not start without vigorous and continuous pumping, Ive tried dozens of times with dozens of different initial pump amounts.

I have not adjusted the float and have not looked into a fuel pressure regulator. I will try those out right away, thanks!
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Old 11-08-2015, 11:59 PM
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By the way, Do you have a suggestion for a Fuel pressure regulator? Looked on Jegs and summit racing and there are hundreds of the damn things. Only a few went down to 4 psi, but if anybody knows a good one for my situation, I would love to hear it.
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Old 11-09-2015, 07:52 AM
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a spoon-shaped eating utensil with short tines at the tip

Last edited by Spork; 11-16-2015 at 10:46 AM.
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Old 11-09-2015, 09:08 PM
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If you have to pump the bejesus out of it to get it to start, you probably have a bad accelerator pump diaphragm. Simple enough to check with an assistant or if you have a really long arm. If neither is available just disconnect the throttle linkage from the carb to check it.


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Old 11-10-2015, 11:19 AM
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Hi Peter, thanks for the input, I thought of the accelerator pump as well. However, wouldn't a bad accelerator pump cause power loss problems when under load? Once the boat is started and warmed up, It pulls skiers out of the water flawlessly. Ive had a bad accelerator pump on my old holley, it lost power during an aggressive start when pulling up a skier. Would a bad pump only reveal itself during a cold start like this? Still, I will look into that when I take it to the shop. Thank you.
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Old 11-10-2015, 11:20 AM
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And thanks James for the shopping link
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Old 11-10-2015, 12:02 PM
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Yeah, hole shot would be terrible too if the accelerator pump diaphragm were bad. Have you checked for a base gasket leak? A leak would make it run lean, and once warmed up, leaks can be less of a problem.
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S5 WHEEL PACKAGE - FREE SHIPPING
TWO WHEELS W/ST205/75R14 KENDA TIRES $299
TANDEM AXLE PACKAGE W/205/75R14 KENDA TIRES $599
TWO 5 LUG WHEELS W/ST205/75R15 LRD KENDA TIRES $349 S5 W/BLACK INLAY
TWO 6 LUG WHEELS W/ST225/75R15 LRD KENDA TIRES $359 S5 W/BLACK INLAY


$99 LED LIGHT PACKAGE - FREE SHIPPING

REBUILDING HOLLEY MARINE CARBURETORS - $235 DELIVERED
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  #10  
Old 11-10-2015, 12:50 PM
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Hi Peter, I did a quick check on that. checked around the ports to see if they didn't get plugged properly, didn't find any issues. The guy who installed it said he did a base leak check upon installation. I'm not sure how in depth of a check that was, especially since he gave it back to me with this problem. Vac leak if definitely on the list of suspects. Its just such a weird problem. Ive had vac leaks, accelerator pump problems, bad fuel, all previously in this boat, and Ive never had to pump the throttle like this to get it to start. Even more frustrating considering the carb is brand new in September.
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