vacum secondary

[sftbll5]

my 90 sunsport is still having idle problems the secondarys will not close completely after hard throttle starts and it results in high rpm idle. wtf I have tried cleaning carb oiling linkage and as much as I can think of in the driveway when I get out on the water it still does it. I can not get it to do this on the hose because there is not enough vacum to hold in the secondary with just throttle and no load. ANYONE with any advice please post

we still wake board every weekend but no sking till this gets fixed

[DKJBama92Mariah]

A holley marine carb uses vacuum operated secondaries. The engine vacuum acts on a diaphragm to overcome the pressure of the secondary spring to open the secondaries. Sounds like your secondary springs may have gotten weak or the diaphragm is icky and sticky. Have you had the carb rebuilt? If not, it might be a good time. Not a definitive conclusion, just my first guess. What is the part number on the carb? On a holley, it will be etched on the outside of the choke horn. Get the number for us and maybe we can provide some more input.

Cheers,
DKJ

[sftbll5]

Ok I have been after this for a while and I think vacum is holding butterfly open, when I removed linkage to secondary and manually opened it while engine was off it would snap back closed but with engine running it stays just barely open enough to increase idle, In the spring I tuned up electircal parts Cap rotor wires plugs breakerless points along with new pcv valve and cleaning carb and spark arrestor did not have this problem last year could it be timeing is off and it is increasing vacum just geussing but still looking for second opinion.
Thanks for the help
sftbll5
couldnt get on water, tow vehicle broke this week so Im in maintenance mode

[DKJBama92Mariah]

Well, you have eliminated two potential problems; the butterflies binding in the carb body and the secondary throttle screw being out of adjustment.

That leaves three other things that could cause them to stay open:

(1) The linkage that connects from the vaccum actuator to the secondary throttle shaft could be binding up. This is illustrated in number (3) below. You seem to have checked for this so i'll move on.

(2) There is also a linkage that connects from the main throttle arm to a fitting in the secondary throttle shaft. This helps to close the secondaries completely when you close the throttle to idle. This linkage could be bent, binding, or gummed up. Here is a pic of what i'm talking about.

http://img.photobucket.com/albums/v55/dkjpika/Boat/Carb1.jpg




(3) On the other side of the carb is the linkage that connects the secondary shaft to the vacuum actuator. The actuator is the black housing circled in red in the picture below. When the engine reaches a high enough vacuum, the vacuum sucks on the vacuum diaphragm overcoming the pressure of the secondary diaphragm spring that is inside the housing. When the diaphragm moves up, it pulls on the linkage that opens the secondaries. The spring inside the actuator could be worn or broken causing the very small amount of vacuum at idle to partially open the secondaries. Here is another pic of this assembly.

http://img.photobucket.com/albums/v55/dkjpika/Boat/carb2.jpg


These pics may look a little different than your carb. Mine is a 4010 which wasn't used by PCM for a long time. I would guess yours has a 4150/4160. It doesnt matter though; they all pretty much work about the same.


I'm leaning toward either numer (1) or (2). I just mentioned (3) to be thorough. I feel it is less likely that the secondary spring is the problem because that could cause you other running problems and HORRIBLE gas milage, but it is still a possibility. I am assuming that the boat runs fine other than the idle because you didnt mention anything else about it.

Number (2) is my prime suspect because, in theory, that linkage should FORCE the secondaries all the way closed when you close the throttle. Also on this subject, if your throttle cable isnt letting the throttle arm go ALL the way back to the idle position, this linkage wouldnt completely close the secondaries.

Number (1) could also be it. You said you cleaned every thing up, but double check where the linkage goes into the vacuum actuator housing and make sure it isnt binding up.

NOTE: When you're checking all this out, i would advise taking the time to pull the carb off the boat and take it to a workbench. This way you have better lighting and better access to all of the linkages because you can turn the carb any direction you need to instead of having to continually go to each side of the boat and squat down to look.

Also, dont take offense if i've dumbed this down or tried to explain too much. Its just more time efficient to write as much as i can about it just in case you dont know exactly what i'm referring to.

OK, back to work. I've got a secured transactions final in 6 days. I'd love to just have the opportunity to work on my boat, but i have to settle for just taking about them here.

Good luck and hope this helps. Holla back and let us know what you find out.

Cheers,
DKJ

[DKJBama92Mariah]

sftbll5,

Did you ever figure out the problem? One of the main reasons i post here is because i like sharing knowledge with others, and i know my way around a boat pretty good. Another is that i LOVE being right. It always makes each of us feel great to know that we've helped someone out. So, if you worked the problem out from our advice, please let us know. If not, im sorry, and at least let us know if we can offer any more advice or if you found out what the problem was.

Cheers,
DKJ

[sftbll5]

had boat out and found that if you shut engine off it allows the butterfly to close? to much vacum ? reset timing to book specs 10btd but noticed it was less responsive changed back but still ???? on secondary does the linkage push the butterfly closed when throttle is not into secondary?
Thanks for any input only thing I have not been able to figure out on my DREAM BOAT!
sftbll5

[SkiLew]

My boat seems to be doing something similar see my note: Have you fixed the problem?

Has anyone had a problem with their engine wanting to idle too high after it has been run real hard.

I Have a 1993 351 engine with the standard Holley Carburetor. Sometimes after I have run the boat really hard the idle rpms will be so high that I am afraid to put it into gear for fear of damaging the transmission.

If I shut the engine off and let it sit for just a minute or two and then restart the engine, it will usually idle normally.

Again this only happens when it has been operated at nearly full throttle conditions.

Any thoughts?

[sftbll5]

I think ive got it fixed! I believe it was the linkage, it seemed to not help the secondary close completely after some bending of the linkage rod and tightening connection at primary it seems to be running correct with no high idle . I have no idea how it got that way I think maybe it was rod connection at primary bieng loose, some small washers did the trick.

Dont let go of the rope.
sftbll5