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Discussion Starter · #1 ·
I been slowly tying to chase down the problem ant not really sure where to go now? At idle in neutral it runs perfect. In drive but still idling it surges, i guess thats the word i am looking for. haha When i give it some gas to get on plane it breaks up a lil then full throttle runs fine. I have changed the cap and rotor, new plugs, checked the flue water separator. Next i was going to do wires but would that cause this? Also i just put new heads on the boat in the spring do to one being cracked when i bought it. thank you for any advice you might have
-chris
 

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I would consider rebuilding the carb and the possiblity of a weak coil. Does this boat have points? If so I would get rid of them for the pertronix solid state system.
 

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Well, it does sound like it's a fuel delivery/induction problem to me, if it's carb'ed , I'm thinking a power-valve or accelerator pump problem..
It would help to have some more info on your engine..
 

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Discussion Starter · #4 ·
it is an 87 bbc 330 hp. i was thinking coil also maybe i should try that first? or check into the carb? thanks for the help so far! :D
 

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I agree about the coil, it has been my experience on street cars and my own boat that the coil has been changed because it is an easy suspect, but it has never been the problem. But it might be an excuse to upgrade the coil to eliminate any possibility, I run an MSD. I would change the wires, seems as though lots of times they are the problem, could also be a cracked plug, you could pull them all and check for evidence but at that point you might as well replace them. It seems as though the missing is a ignition problem of some sorts, but the surging seems more likle fuel. Being an 87, I assume you have a q-jet carb(which don't have power valves like a holley) so thats probably not it and you should have a thunderbolt ignition, which it electronic. Have you removed the anti-siphon valve in the tank? seems as though lots of times thay are a source of fuel delivery problems.
 

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Discussion Starter · #7 ·
no i havent and your correct about the thunderbolt and q jet carb. I am stumped. Its been gettign me to the cove and not really giving me a problem so i have just been dealing with it. I dont no where to start. If there a fuel filter that can be checked? there hasent been much done to the boat while the previous owner had it. It only has 300hrs on it but 20 years is a long time! :confused1
 

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check the main engine wiring plug(cannon plug)where it attaches to the engine. Undo the clamp, pull to off, inspect it for burnt pins. Make sure when you reconnect that it goes all the way on (push really hard and wiggle just a bit). I have seen a lot of running problems related to the cannon plug only making partial contact. just a thought.
Joe
 

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Discussion Starter · #9 ·
cannon plug? where is that? i have never heard of that. I am new to this carb stuff!! I no fuel injection! lol
 

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the "cannon plug" is on the top of the motor, on your vintage it should be on the left side as you are facing the outdrive, it has a hose clamp on it, loosen clean with brass brush, add dielectric greases and reinstall, I have never seen this plug be a problem though. There should be a spin on fuel filter/water seperator on the same left side-it looks like a oil filter, I would replace that first, also there is a filter at the inlet of the carb(you will need two wrenchs) take it out and check it, but this usually isn't a problem as most of the debris is caught at the spin on. Really though, I would get rid of the anti-siphon valve in the tank. Overall, if your boat has been a little maintance deprived I would check everything, including timing- (I don't think this has anything to do with your problem) but it is always good to make sure it is right. Your bbc should be at 8 degrees, idle below 650, if you run premium you could go as much as 12 degrees. If you are used to efi you will be amazed how easy it is to work on carbed boats, it's like a 1960's car. :winker: -Paul
 

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I just noticed I have the exact same thing going on as Chris. Also a 454 (330HP) carb motor. I have new plugs, cap/rotor and carb. It seems to do it when I am running on plane, a drop of 200-300 RPMs just for a second, then back on again. Its consistent in time/rythm. I was thinking a bad plug or plug wire and I was also going to try a new coil. I never thought of a fuel/water problem because its so rythmic.

mark
 

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35thls1ss19 said:
I been slowly tying to chase down the problem ant not really sure where to go now? At idle in neutral it runs perfect. In drive but still idling it surges, i guess thats the word i am looking for. haha When i give it some gas to get on plane it breaks up a lil then full throttle runs fine. -chris
Another thing to look at is the choke. It could be partially closed and run fine with no engine load, then you add engine load and with the A/F richer it surges.

As you give it gas to plane, once you push throttle passed certain position there is a 'tang' on the carb linkage that will open a closed choke.

Maybe this is what you are feeling ????????????
 

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BTW: For people with Quadrajets, they are very old ! And are getting older by the day. They are so dependable that when one actually starts to show issues, we never think the carb is the issue.

I did the same thing a few years back. My engine carb was from '91. Boat started to lose a little top speed. I started with tune up. No better.

Over a few weeks the boat started to labor a little on plane. Changed seperator and removed inti-siphon valve. No better.

Few weeks later it really struggled to get on plane.

Compression test, fuel psi, ignition check, and etc was done and all looked good.

Few weeks later boat really did not want to get on plane. Installed my lower pitch prop and still didn't help.

Decided to pull carb finally and gave to local 'carb expert' and put on boat. Boat would not plane ! F**k !

Brought truck to truck scales at our recycling facility. Weighed it. Came back with trailer and weighed truck and trailer. Came back with trailer, truck, and boat and weighed it. Did this to get weight of boat because now I'm thinking this performance issue maybe somehow boat became waterlogged.

Weighed 3000lbs. Manufacturer listed it at approx 2800lbs. I had about 1/2 tank in it and gear so that couldn't be the issue.

Bought new BG650 carb, installed, and boat leaped on plane, way faster than ever, and got new best top speed on first run. Played with secondary springs and boat now was an absolute animal getting up on plane leaping right out right now.

Checked out quadrajet later and found why it even ran worse after local expert touched it. Secondaries wouldn't open.

So a note to everyone: if you don't think secondaries are used much for getting on plane with a single engine - you are dead wrong as I was !

Playing with secondary springs (going to even less tension - ie: quicker secondary opening) some more on the BG carb, it get's out of the hole even faster.
 

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Discussion Starter · #14 ·
thats where my problem is.. getting on plane. it breaks up ....... give it some more gas and bam it goes! Then on plane it seems to run fine. I have had it drop 200-300 rpms just like mike said. But lately full throttle its been running great. But while idling threw the cove it surges. Jumps up 100- rpms or so? think it could be a carb problem?
 

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I have a new Edelbnrock 750 on mine. The secondary springs, are those the 2 screws on the front with the springs? According to the instructions I reversed (loosened) them out about 4 turns.

I'll have a look at this again, the looser they go the quicker the secondaries open up? Can they be too loose?
 

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Leud Conduct said:
I have a new Edelbnrock 750 on mine. The secondary springs, are those the 2 screws on the front with the springs? According to the instructions I reversed (loosened) them out about 4 turns.

I'll have a look at this again, the looser they go the quicker the secondaries open up? Can they be too loose?
Those are the idle mixture screws... Edelbrock carbs have mechanical secondaries. However, the secondary air valve is adjustable.
 

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Hey guys, none of us can guess what your actual problem is unless extremely lucky/coincidence.

You have to go in and check things. After further diagnosis we may possibly be able to help more.

More information on your end will create other things we'll throw against the wall.

A carbureted engine is relatively simple. Air/fuel/spark.

Although simple, you must understand each component / how it works / how it is working/ and the specs to how it should work to do a better diagnosis.

Without any pertinent info, we can only throw things against the wall to see if it sticks.
 

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Discussion Starter · #18 ·
well thats where i am stuck haha. sorry for my ignorance but i no just what you told me. spark air fuel. Like i said i have only worked on fuel injection on a car.

So i changed the fuel water separator, plugs, cap rotor, check compression, now today i am going to check my fuel filter before the carb. Other then that i am lost? How can i tell if the carb is adj. right? What kind of things do i need to check now to further assist you guys into helping me? thanks again for your time a patients with me.
-chris
 

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I think it is a carb issue. Has this carb ever been rebuilt? I think I would try a new carb.....CFM has almost always been great source of information. Can you borrow one...for a short period to try?
 
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