Hp 500 carb setup help
 

Have a brand new carb on my hp 500 model year 1999. It is a Holley 850 marine carb. Having some trouble getting it set up right it's surging around 3500 rpm down a few hundred and back up. It came with 88 in front and 98 in rear I changed to what the old carb had 77 and 88. Brand new 850 had a power valve in the secondary. I changed it out to the old non power valve secondary metering block. So my questions are what is the jetting to run? should I leave what it came with it? Power valve secondary metering block or no. If so what size valves? Thanks for the help Also it starts right up cold. After sitting for ten mins once hot it cranks for 10 seconds or so before starting. I noticed with the arrester off a small amount of fuel coming in down by where the throttle plate is and running into the carb. Maybe the old metering block I had on there is a problem. ??

Put it back to how it was shipped. It should have had 96 jets in secondary? Your old carbs were smaller and therefore won't meter fuel like the new ones. Smaller carbs like smaller jets. As for the fuel leaking, loose bowl screws can lead to a carb leaking internally. If you want to block the rear pv on the 850 marine carb you'd want to jet up about 6 sizes in the rear. Put it back to how it was shipped , go run it, and report back.

Oh and don't swap metering blocks from other carbs to your new carb.

Did you have this problem when you tried the carb. the way it came from holley? 98 jets seem pretty large with a powervalve.

I never tried it the way it came. Going to put it back that way and try it and ill check back. i think it did have 96 in the rear.

I am assuming they are the R80443 marine 850 carb?

I have these carbs on my engines, but with roots blowers. Two of them per engine. As of right now, they have 88P/96S, with 10.5PV in front, 2.5PV in rear. (blower deal). I too thought the stock jetting was way too much, but the wideband told me otherwise. I have buddys with similiar roots blown setups, running way less jet in their carbs, but making more power than me and bigger cubic inches, etc, but different carbs.

Mine are blown 468's. When I bought these carbs, they had came off of a blown 572. I took them apart to rebuild, and saw they had 96P/96S, with 6.5PV front and rear. I thought "geez, thats a ton of fuel, guy who set these up must be silly". But in reality, they were prob right on. I jetted them 84/92 with a pv just in the primary for my engines. They were simply too lean.

I am not surprised, that taking 20 jet sizes out from stock, plus blocking the rear powervalve, is making them lean for you, which is probably causing the surging condition you are seeing.

Wholly schit !

Jetting is not the same from carb to carb so get those jet's you swapped out of there !

Surging could possibly be lean surging.

If you do not want the PV in the rear, put a power valve plug in there , jet the secondaries a few, but do not change the metering block.

Oh my gosh.

Also when it is idling or shut off you should not see any fuel coming out of the boosters or any where else.

x-2

What power valve do you have in the primary side? My first guess on the fuel dribbling issue would be that you have the wrong PV in there, and it is opening at idle and dumping fuel. That would explain why it runs fine when cold, because then it would actually need a little extra fuel until it reaches temperature.

As other said, put it back to box stock and run it, and then report back to us. Honestly, you are flying blind on this deal without any kind of wideband O2 sensor to tell you if you are lean or rich. It is very hard to get any decent plug readings with all of the ethanol and oxygenators in today's fuel blends, and even then, it takes someone with some experience to read plugs correctly. Be very careful, because you could be treading on some thin ice here. If in doubt, always jet on the rich side for a marine application. Lean kills!

6.5 primary. after work gona put the powervalve back in the sec put the jets back it came with and run it. Thanks for the help as i do not know much about this stuff except setting float heights. What is the diffrence when you have a powervalve in the sec vs. no pv?

Even if he had a 10.5 PV in there, fuel shouldnt dribble at idle. Alot of guys think that if a powervalve opens at idle, it makes it dump fuel in the engine at idle. Not so. The powervalve simply add's fuel to the main well, which is then fed to the boosters. If the PV were opening at idle, its no different than how it would idle if he installed 6 size larger jets and plugged the PV.

If a powervalve is BLOWN, then yes, fuel will be sucked past the torn diaphragm, and sucked into the engine, below the throttle blades.

The sole purpose the idea of plugging the rear powervalve, came from drag racing. Under hard acceleration, the fuel in the bowl would go to the back of the rear bowl, uncovering the powervalve, rendering it useless. Really not an issue with boats.

Great info!

I would revisit float settings & make sure your not running '80s pre ethanol specs ,some boats can get pretty angular planing out and will benefit from bowl vent baffles rear pv delete and sometimes even rear bowl jet extensions .see if you can tell if surge starts when secondaties open or not 3500 rpm may be still all in primary side

Thanks. The power valve is a very simple concept, but confuses so many people. From things like a 10.5 PV will flood the engine at idle, to confused about how they open/close, and the fact that the size of the restrictions in the metering block, determine how much fuel they add. For example, when the PV opens on a Dominator, it will add much more jet size worth of fuel, than a stock 750 holley. So the idea of generally saying "plug your PV and go up 6 sizes" may not always be the same case from carb to carb.

Example. ICDEDPPL has some Nickerson 850's. They drilled the powervalve restrictions out, to around .093 if I recall. Which is dominator territory. Just by plugging his rear PV, his AFR leaned out a full point. On my stock 850's, by adding a rear powervalve, my AFR richened up about .4-.5. Which makes sense because my power valve restrictions are about 1/2 the diameter of his.

I dont agree with what Nickerson does in that area. So far I've seen a few of his carbs, where they are very lean at cruise, and go pig rich at full throttle. It took alot of work to get ICDEDPPL's AFR's to be within reason. IMO, nearly 14 AFR at 3200 RPM cruise, and low 10's at WOT, is not a very good fuel curve. My fuel curve on my engines, simply goes from about 12.5 at light cruise, to 12.0 at fast cruise, and 11.3 at full throttle. Theres no reason to have a 4 point difference from 3000RPM to WOT on a blown marine engine. What I really love about the modern technology of being able to install a wideband on your engine, is it really starts to show who can, and who cannot, setup a carburetor. For years we all thought "Im gonna have Dean Nickerson, Pat from Prosystems, Chuck Nuyyten, or whoever, build me a carb that will be perfect for my application". IMO, nobody can build a carb to be perfect out of the box for the application. There simply are too many variables. Can it run, sure it can. A 600HP 540 in a 23FT cat, is not gonna need the same setup, as a 600HP 540, in a 38 Top Gun.

Too many times guys set up a carb on the dyno, then put the engine in the boat and it wont idle worth a dam. They forget that the boat might be swinging 18x34P cleaver props, and it actually may need some air/fuel from the idle circuits when shifted. Or, they forget that even though the fuel mixture at 3400RPM looks great on the dyno when all 4 barrels are wide open, that it may not be in the boat when the secondaries arent even open yet.

IMO, in 2014, the best deal going, is a quickfuel carb. The hardware you get is great. They look great. The price is great. The metering blocks are billet, along with the baseplates. The carbs are infinitley adjustable, from air bleeds, to emulsion bleeds, to idle feed restrictors and PV restrictors. Get a wideband, a case of beer, and go do some carb tuning. You'll end up being much further ahead of the game, and have an engine tune that will be safe, and pay for itself in fuel savings after its tuned properly.

What effect do the air bleeds have on the way the fuel is metered and how? And at what phase of operation are they effective? I have pro sys dominators and would like to do some fine tuning.

Jiffy,

The Holley OEM specifications are typically very close (and safe) in stock or mildly modified NA engines. Creating modifications that are not supported by data will not only destroy your baseline but often result in significant damage. I would suggest you return to spec to establish a proper baseline, working outward from that point after you accurately determine what fuel delivery adjustments the base requires.
Holley No. 80443 - 850 CFM Mechanical Secondary

Primary - Port 88, Stbd 88
Secondary - Port 96, Stbd 96

Power valve –
Front 122-65
Rear -122-35

Accelerator pump - Primary - 30cc, Secondary - 50cc

Accelerator nozzle - Front - .031. Rear - .031

If you will be attempting to tune based in part by plug reading, you will find the following attachment (Credit; Larry Meaux) instrumental in your success. obtain a quality plug light (10x) and be aware, reading unleaded, ethanol fuels, requires updated skills.

Bob

To build on what MT is saying about dyno runs not translating to real world conditions on a boat, when I had my engine dyno'ed, I asked them to run a steady state test at a typical fast cruise RPM under load, just to make sure I wasn't going to go lean or have any issues with oil drainback. (I am running screens in my lifter valley with a HV pump and 8-qt pan - a whole 'nother thread is devoted to this, so not going there. ;) ) When we ran it this way, we found that it was running much leaner than it had been under the quick full throttle power pulls earlier. Header primaries actually got hot enough to start glowing! Needless to say, if I had just dropped it in the boat without running this test and making the necessary adjustments, I would have burned it down. As MT has said, running on the dyno is great for breaking an engine in under controlled conditions and getting a baseline tune, but there is no substitute for actually running it in the boat with something to tell you what is actually happening in the engine in regards to fuel mixture. This is where the advent of wideband O2 sensors has been so helpful.

Great info Bob, thanks.

IMO, high speed air bleeds should not really be messed with, until you have run out of basic jetting/powervalve tuning. I have found that air bleeds can tweak things a little, but usually not enough. They can change the "shape" or timing of the fuel curve so to speak, which I think can be more beneficial to the automotive world, where rpm/load is constantly changing. Everything in a boat is more steady state. The idle bleeds can change things around as far as idle goes, but so can the idle feed restrictions (idle fuel jets). If you have screw in idle feed restrictors like a quick fuel carb, playing with those would probably be of more benefit than the idle air bleeds.

Guess what I am saying overall, is generally working on the fuel side of things, is of greater change, than the air side of things.

Although in the world of carburetors, stock holleys gets looked at like they are always able to be improved on. You tell a guy who spent 3 times as much for his custom carb, that a stock holley would probably work better, he will usually tell you otherwise. IMO, holley has been manufacturing carb's for a very long time, and the aftermarket guys have been modding them for a long time as well. Some for the better, but mostly for the worst. The 80443 carb, came with that jet combo for a reason, they just didnt say "umm, lets throw these in here and see what happens''. They know people want to bolt a carb on and run the boat.

RMBUILDER pretty much summed up what I been trying to say, in 1 post lol. Put the carb back to stock and run it. Adjust from there. The idea of just throwing the jets that came from your HP500 old carbs, thinking that the engine will be fueled like it was, doesnt apply.

As far as reading plugs, for years I have been told by guys to look for a coffee colored porcelin on the plugs. IMO, that statement is incorrect, as is any reading you may take, after going wot, coming back to idle, and letting it idle for a bit before shutting down. Pulling plugs after idling back to the launch ramp, is worthless. That tells you pretty much nothing.

When you look at modern fuel injection, the great thing about it, is that it can maintain a clean steady fuel mixture, at all throttle positions, all RPM points, and all load conditions. It does this via feedback in nanoseconds, and can constantly correct itself. To attempt to get within a mile of this, using a carburetor, you also need feedback as the tuner. A carb will never be as good as EFI in this area, for alot of reasons. But, IMO, the feedback from pulling a spark plug here and there, simply will not get you within a mile. At least not to the point of "oh, i need to change my high speed bleeds .002, that should do it", or "Im a tad rich at 3300rpm, but a tad lean at 3600RPM, so let me change the PCVR by .007". Without a doubt, reading plugs is still mandatory, and can save you from meltdown mode.

But, think of it like this. You think you're wife is screwing around on you, but have no proof. You can hire a private detective, to check on here whereabouts randomly at 8am, 12pm, 5pm, and 10pm. However, theres still a good chance, she might be bent over a leather couch taking it like a champ, at 2pm somewhere. Best bet is hire a detective to stay with her from 8am-10pm to get your answer. Having a 02 sensor at least will monitor the fueling from idle to wot, where you can watch it live.

Man they really went fat for the 500 s the old 540-dominator deals were I believe 92 square

Mild Thunder are the power valves different front to back?

Ok. Put the secondary metering block that came with it back on with 96 jets and put the jets it came with back in the primary. Cold start it lights right off. When I rev it at the dock it sounds very strong and has no hesitation. Gets on plane nice and fast doesn't loose any rpm. Once up and cruising at 3300 or so it will drop down to 3100 then come back up few seconds later. I get the same rpm drop from wherever I am. So at 4k it will drop to 3800 or so. And back. I did go wide open once it comes in and it will bog then start to pull then bog again. Float levels are correct. Gona chnage fuel filter for the hell of it today

What's the fuel pressure doing when the bogging happens? Sounds to me like you may have a fuel supply issue. Like a bad pump, clogged filter, etc

Can you actually feel a loss of power when this happens, or is it just indicated by the tach? In addition to fuel supply issues, it's also possible that some junk got into a passage with all the tinkering that was going on with the carb.

Went back and looked at your original post, and I'm not clear if this is a single or twin engine application. Is this the 353 in your avitar? If so, did you replace both carbs, or just one of them? If you did both, and the surge issue is happening with both of them, then it sounds like it is probably fuel supply related.

Are you still seeing the fuel driping down by the throttle plates when you shut it off?

yes, can feel it in the boat. dont have fuel psi gauges. one carb is new, surge is only on one motor with new carb. have been having problems all year with this motor. im gona change the filters tonite and re try. i have stock metal hp500 feed lines to carbs, so no inline guages. i may make up some lines with guages.

What ignition do you have?

I'm wondering why the original carb(s) where replaced.....

Wouldn't happen to be the same issues you are having now, would they ?

Sounds to me like you have another issue. Whether it be a bad fuel pump, clogged filter, or an ignition problem. My guess is the new 850 carb was purchased in an attempt to fix that problem?

Starting with throwing a mechanical fuel pressure gauge on it, would be a good thing. Watch for drop in fuel pressure. If fuel pressure holds steady, I'd start looking at the ignition system.

i couldnt figure out the other carb it was dumping fuel in at idle. the surge is new...just started few days ago. have stock ign that comes with 99 hp500 new plugs wires cap rotor coil etc. someone was chasing a problem on this motor before me. with my luck its not so simple as the fuel filter but well see.

Did you try switching carbs? Do you still have the original HP500 carb? I would try taking the carb off the good motor and install it on the one having trouble, then put the original carb back on the good motor. That will rule out the carb if no change. Often issues like surging and stumbles are thought to be fuel/carb issues, and end up being ignition problems in the end.

You are going to have to put a fuel pressure gauge on it!

Compression test and fuel psi test are always 1st when chasing a driveability issue !

headed there...thanks guys ill update

will check that tonite

Changed fuel filter and restest no change. Going to get some fuel pressure guages, and swap the carbs tomorrow. The boat gets on plane perfectly, then about 30 seconds later cruising at 3300 it starts. Its like clockwork, drops 200 rpm, gains it back 30 seconds later and continues. once i get fuel psi gauges in and swap carbs ill be able to rule out some more hopefully. This is driving me nuts!

and yes the fuel is still dripping in brand new carb i dont understand that!