replacement carburetor

[spudski67]

I have a 1990 sunsport with a pcm 351. The old carb is a holley 4 barrell with electric choke and the square float bowls. I do not know the model number, though. Can anyone help me with available replacements/refurbished carbs? What will work? Does it matter whether its holley or edelbrock? I want whatever will bolt up the easiest. Thank you

[Supra-in-steamboat]

Skidim.com has rebuild kits for @$50. Personally I would stick with the Holley- you already are set up for it. If you are not experienced with carbs, I would let someone else do it- lots of small parts and at least one specific tool. As far as the model number- there are a couple of tags stamped on your carb that should have info. Take the flame arrestor/breather off and poke around, sometimes the number is on the side. If you still can't find it, bring it to Napa, Carquest and maybe one of the good ole boys can find a number on that Ford. Good luck.

[spudski67]

I suppose I would consider doing a rebuild. I've been having all sorts of trouble with the carb and thought it would be nice to just start fresh. But I guess I'd only be out 50bucks if I mess up a rebuild. I'm pretty sure the floats are shot so I would have to replace those in the process. Does this add much difficulty? What is the special tool required? How tough is the rebuild for an amateur if I go slow and careful?

[rludtke]

Holley carburators are expensive, and completely and easily overhaulable, so unless money is no object, I recomend trying other alternatives first.

Your carb is a Model 4160, part number 0-80319-1 http://www.holley.com/0-80319-1.asp.

As mentioned overhaul kits are availbile for ~$50 at skidim, and I have found them for ~$25 on Ebay stores. This kit will replace all of the commonly affected parts and gaskets, including the primer, the power valve, and the two needles and seats. It will not replace the floats, but the floats rarely fail.

Other things the kit will not do is replace the throttle shaft bushings. If worn excessivly, unmetered air will leak, creating a lean mixture. This condition can be checked for by feeling for excessive play of each shaft in its bushing (meaning the inside diameter of the bushings are noticably greater than the outside diameter of the shaft). The bushings, shafts, and the floats can all be ordered individually from Holley if needed.

Holley's website has instructional documents for your carb here: http://www.holley.com/data/Products/Technical/199R9808.pdf

And an exploded view parts illustration here: http://www.holley.com/data/TechService/Technical/4150-4160%20Exploded%20View.pdf

Installing the overhaul kit is really simple, with no special tools required. Cleanlyness is everything, and don't touch the black Viton tip of the needle valve with your fingers- handle it by the retaining wire.

The biggest benefit of the kit is probably the replacement of the needle and seat. The fuels we use are full of solvents in the refined fuel mix that allow the needle and seat to rapidly wear at the microscopic level. The carbs are sensitive enough that this can matter. If you can visibly see wear on the needle, then the parts probably have been in need of replacement for some time.

One trap I fell into was my inspection of the inlet screen. I noticed that I had one, and that it was clean, but I failed to note that it was not fully attached, and could open to allow junk to pass. Poke the screen gently with something to ensure that it is fully secure. I added an inline filter downstream of the pump to stop the junk, as I was getting tired of pulling my float bowls apart several times a day.

You don't necisarily need to remove the carb to install the kit, just the float bowls. This can easily be done on the boat. Fuel will drain out of the first bolt to be removed, so I try to catch it in a plastic bottle. Take the bowl and the metering block off the boat and into your work bench (or the kitchen table :) - I've actually replaced these parts on the floor of the boat in the middle of the lake). Replace the parts you find in the carb with what is in the kit. Don't be concerned when you find parts left over, as these kits fit multiple carb model numbers.

Holleys website is very helpful, and should give you everything you need. Post here if you have additional questions or concerns. If you choose to overhaul, let us know how it goes.

Cheers,

[spudski67]

Thank you for the excellent response. Very helpful and I think I will be making an attempt at the rebuild kit.
The main problem I am having is with excessive fuel dumping into the front barrells even after the motor is off. I was having the same problem with the back barrells but some carb cleaner fixed it. The engine floods and rarely starts. I'm assuming its the floats? Any input? Should I replace them when I do the rebuild?

[rludtke]

I've experienced the very same problem. I first overhauled my carb to try and fix the same thing, but have continued to experiance the flooding intermittantly, between both front and rear float bowls. Tearing the bowl apart would often reveal debri stuck between the needle and seat. The result is fuel pouring out the J tube vents on the top of the carb.

Just this season, I pulled the boat out of storage and replaced my impellor. Went to test run on the hose, and it began flooding again. I always have a spare kit or two of parts (because I seem to always have to mess with this dang carb), so I pulled it apart, and found more debri.

Every time I would find debri in the needle valve, I would check the screen and it would look clean, yet stuff would be laying in the bottom of the bowl. Finally I figured it out, the screen was not fully attched. This problem had been with this carb since before I bought the boat. The last owner complained of flooding. I figured I could fix it, but I don't think I completely understood the root cause until now, many years later.

I haven't put the boat in the water yet to be sure, but I think the loose screen has been my elusive culprit. I installed an in-line filter, and replaced the water seperator to make sure no more crap gets into my carb. With any luck, I'll have a flood-free season this year.

Chances are the flooding is being cause by foreign debri keeping the needle valve from closing. The kit may or may not be necisary, but I recomend you do it anyway, and look closely at your inlet screen.

Modern floats are plastic which almost never leak and fill with fuel. The the old soldered brass ones of the past were notorious for leaking and sinking. When you pull your float out, hold it up to your ear and shake it to listen for sloshing fuel to be sure.

When you pull the needle seat out, look inside for junk. Most likley this is the reason for the flooding. Scratches or scoring on the needle could do it too, but the flooding would be much less dramatic then if debri was holding the valve open.

Taking the float bowls off, replacing the parts, and putting them back togather is only about a one beer job. Hook it up to the hose and test run it to be sure you got it right before heading to the launch.

[michael hunter]

The main problems with carburetors are debris,gasket leaks, floats and power valve. The rebuild kit should address all of them. Make sure you carefully remove ALL of the gaskets. Clean every thing with carb cleaner make sure you spray in all the small holes. Then blow them out with compressed air. After its clean follow the directions exactly. I also do not recommend changing to a different brand if the Holly is right it will perform great.

[spudski67]

Im feeling more confident. I think I will give the renew kit a shot.

rludtke - the fuel drips from the vents, not the J tube. Still think it could be something with the needle and seat? Or, would it be worth it to order new floats when I order the rebuild kit and just do them too?

I can't thank you all enough. Your help has been immense. My only carb experience is with dirtbikes when I was young.

[rludtke]

On these Marine carbs, the J tube is the bowl vent- the J tube vents are directed into the engine to reduce the fumes and spillage into the bilge. I suspect that you see excess fuel being metered throught the metering orifices in the venturi. If you see fuel running out the orifices in the primary (or secondary) at idle or low power settings, it's flooding. I still think that crud in the needle valve, or a worn needle valve is the culprit. I think the likelihood of a sunk float is very, very low. it would be easy enough to go back in and replace a float if you ultimately need to.

These carbs are meant to be tuned in-situ, which means they can be taken apart repeatedly on the same gaskets. This is common in auto racing to dial in performance for a tracks environment. The bolt gaskets wear out from repeated tear downs first. The kit includes duplicates of these. Because the marine carb doesn't have an external float adjustment (to prevent leaking), you may need to tweek the float level in-situ (on the lake), to dial it in just right. If it stumbles on acceleration, the level is too low. If it seems to flood a little- rough idle, and you can see fuel dripping or running at the venturi, or if it leaves black smoke, the float level may be too high. I try to bring the float level as low as possible without any stumble on a rapid acceration under a load.