Holly 4bl adjustment

[Payne]

I just bought a '91 Reinell, OMC 4.3 HO with the Holly 4 bl carb. The first trip out showed that the choke was way out of adjustment. I had to rotate it 180 degrees to get it to open. It then idled and ran well, but it idled at about 800 and still smelled like it was running too rich. <br />At home I pulled the plugs and found they were not the factory spec plugs, but a "hot" type. I replaced the plugs with the proper type and went back out. It ran about the same... smooth idle, but a bit too fast and rich. I got it warmed up and in gear adjusted the idle down to about 650. It started running a bit rough. I found two adjustment screws (port and starboard) and adjusted the starboard one richer and it smoothed out. I went to the port side and the screw was all the way in! Any adjustment out caused a rough idle. Screw back in and it smooths out.<br />So. Any ideas what would cause this? Did all the previous owners fiddling somehow screw up the carb? Could running way too rich cause this problem? Thanks in advance.<br /><br />Kirk

 

[Don S]

Re: Holly 4bl adjustment

Since you just bought the boat, it would probably be a VERY good idea to do a complete tuneup, not just change the plugs.<br />Do a proper compression test (How to in link below) new points, condenser, cap, rotor, adjust the dwell (not just point gap) timing and all.<br />and since it's new to you checking everything would be a good idea.<br />Here is a post I did a while back that may help you get going properly.<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=015945#000000

 

[Payne]

Re: Holly 4bl adjustment

The HO is all electronic, no points. I'll do all that, but it runs really well except for the rich idle.

 

[fendersfender]

Re: Holly 4bl adjustment

sounds like a carb rebuild is in order

 

[Don S]

Re: Holly 4bl adjustment

It may very well be the carb needs a rebuild, after all, it is 15 years old. May also be a vacuum leak. Wouldn't hurt to hook a vacuum gauge up to the engine and see what it tells you. <br />A carb being out of adjustment won't permanently damage the carb, it would just need readjusted properly and make sure the choke is all the way open. Being partially closed on a warm engine will sure cause a rough/rich idle, along with a plugged flame arrestor.

 

[Payne]

Re: Holly 4bl adjustment

The choke seems to be working easily and it was wide open when warm. Vacuum leak? Would that be from a bad gasket, or what?<br />Yes, I may have to rebuild it. The completely closed portside mixture screw threw me. I was thinking along the lines of a plugged vent from the throat to the bowl. I guess it wouldn't hurt to shoot a bunch of B100 cleaner down it, right? The worst it could do is not work and I'll have to rebuild it anyway. Or maybe run a big dose of fuel treatment? The secondaries are pretty sooted up. If I can get by without a rebuild my wife would like me more.<br /><br />Kirk<br /><br />PS I just noticed that the accelerator pump is really touchy...just a slight, slight movement (<1/16) puts fuel down the throat. Would that make a difference? Pardon my ignorance, I haven't really worked on a carb in 30 years.

 

[ron7000]

Re: Holly 4bl adjustment

shooting any cleaner down the throat of a carb never solves anything because the problem lies within the carb- in the fuel bowl, needle & seat valve, metering block, main body, and air bleeds. But if the throat and throttle blades are dirty and air is restricted then it will help. Running big doses of fuel treatment, at least in my opinion, never cleans a carb out to make it run better. The solution is a carb rebuild. The good news is it's fairly easy and can be done relatively cheap.<br /><br />With your idle mixture screw settings, both should be at the same number of turns open. Standard setting is 1.25 to 1.5 turns open and you should only have to adjust it plus/minus a half turn at most. You may have a bad power valve which is leaking fuel, which can cause it to run rich and may be the reason the mixture screw was closed all the way to get it to idle. Given the year of the boat and the way the carb was set when you got it, anything other than pulling the carb apart and rebuilding it properly would be a waste of time and money.<br />Also know on those mixture screws, the one that was fully closed, is you can damage them and the metering block by tightening them too hard. With a rebuild kit you get new screws so you should be all good.

 

[Payne]

Re: Holly 4bl adjustment

Well, that seems like good advice and I guess I really should just do it right the first time. Thanks for everyones help.<br /><br />Kirk

 

[Boomyal]

Re: Holly 4bl adjustment

Payne, look down the carb throat while it is idling. If it appears obviously wet down the venturies and over the butterflies it is most definitely a blown powervalve. All the Holley has to do is backfire once, up thru the carb, and the valve is blown.<br /><br />If it is not soaking wet then you might have a float/needle and seat problem.<br /><br />They do make an anti backfire protection kit that can be retrofitted to your Holley. If the carb has to be rebuilt, IMHO, I would find an experienced rebuilder. There are so many parts in that Holley and gasket kits come with parts that your carb may not even use. Most kits I've seen do not come with new hard parts like needles and seats. If you use a rebuilder he can install the anti backfire kit.<br /><br />If it is just the power valve, that is easy to replace. You'll have to get new front float bowl gaskets and bowl screw gaskets. Take it apart and take the gaskets with you. There is one for the bowl and one for the metering plate that holds the powervalve. There are different ones so you should have them with you when you go to replace. Also you'll be able to get the number off the powervalve. I think most marine apps use a 6.5.

 

[Payne]

Re: Holly 4bl adjustment

The engine did most definatly did backfire throught the carb when the choke was so badly adjusted. And who knows what the original owner did.<br />Power valve... that sounds very likely! And something I am capable of doing. The only question is whether the starboard needle or seat was damaged by closed tight. Is that something I could see visually? <br />I'll go out and and start it up today. It's a lot easier now that I don't have to winterize it every time I start it.

 

[Payne]

Re: Holly 4bl adjustment

Well, I went ahead and rebuilt the carb. It wasn't as bad as I thought; I just had to lay out the old pieces in order and match them up with the proper new gaskets. The vacuum secondaries and accelerator pump were just OK, but would have failed in a year or two. The power valve was the main problem and also one of the little vent holes was blocked. The backfire protection kit took a while to figure out, but makes sense once I figured out how it was supposed to work.<br />The engine fired right up, but I am having trouble getting it to idle smoothly. I gather that you have to have it under load to adjust the idle needles? I will do that this weekend out on the lake.<br /><br />Thanks for your help and advice.<br /><br />Kirk

 

[ron7000]

Re: Holly 4bl adjustment

you should be able to get it to idle smoothly out of the water right down to 700 rpm.<br />You don't have to have it under load to adjust the idle mixture screws, at least not to get a smooth idle.<br /><br />can you desribe the idle problem?<br />does it idle too fast and not want to come down?<br />does it lope when you lower the rpms down to 600-800?<br /><br />when installing the new power valve, you used a new gasket with it and it fit properly? when you screw the power valve into the metering block, if you hold everything perpendicular to the ground the pwr valve gasket can drop down and not seal. The way they tell you to do it is hold the metering block upside down and screw the pwr valve upwards, so the gasket lays flat on the pwr valve when you turn it clockwise into the metering block.

 

[Payne]

Re: Holly 4bl adjustment

I guess the best description is that it idles too fast and dropping the idle speed adjustment makes it rough. But I think it is a linkage adjustment because I can manually move the linkage and it drops to 600. The idle problem is more of a roughness; the engine shakes some and the adjustment of the idle screws doesn't change it until a very lean condition makes it rougher. I don't really remember how I installed the new gasket, but I rebuilt it slow and methodically, double-checking everything as I went.<br /><br />On the bright side, I don't see any wetness in the throats and it doesn't smell rich. Floats seem to be adjusted fine and it smoothly runs up cruising RPM with no hesitation. This engine has apparently been running with this bad carb for some time. I plan to run it in the water for a while at WOT to blow it out some, then see if I can fine tune the idle mixture. I haven't tried to adjust the linkage yet, but I think it just needs a small amout of tightening to fully close the linkage.

 

[superpop]

Re: Holly 4bl adjustment

Did you check the timing yet. I did the same thing on my motor which is the same as yours and that smoothed it out a bit. The manual says 550 to 650 RPM is reccomended but I cannot get mine below 600 without it really lopeing. I think 650 is about right for idle speed though.

 

[Payne]

Re: Holly 4bl adjustment

The HO has electronic timing that changes depending on the octane of the fuel. The idle isn't so rough that it dies, just not the "purr like a kitten" effect that I am aiming for. I agree that 650 is the goal to shoot for. It doesn't want to run at 550, but runs great at 800. I'll report back after I get a chance to really blow it out and then fine-tune it.

 

[Payne]

Re: Holly 4bl adjustment

OK, after a weekend of wot, it idles nice and smooth at 650. But it doesn't back all the way down to idle from the controls and is getting hard to shift in and out of gear. So I guess I need to decide if I am up to the cable replacement, or have a shop do it. Ain't boats fun?

 

[Don S]

Re: Holly 4bl adjustment

You aren't going to get that engine to idle as smooth as a V8, it's an older 4.3 without the balance shaft to help it idle smoother. <br />I think it was 93 that was the first year of the 4.3 with the balance shaft.

 

[Payne]

Re: Holly 4bl adjustment

Yes, it doesn't idle as well as a V8, but it idles as well as it did before my carb rebuild.<br />I sent the boat in for the shift cable; I didn't feel up to trying to remove and install the drive by myself. The shop is charging $295 parts and labor which seems reasonable.