Hard start and rough idle

[acuraguy81]

I am sure the carb is original to the boat it is a 1990 omc 4.3. Im having issues starting the boat has to crank for a bit to fire then it idles rough have to keep the revs about 1000 to keep it running decent most of the time. The boat runs great so im guessing the carb is old and needs rebuilt or replaced. Any tips on what cab to put on, it has the 2 barrel holly now. PS I have fully tuned up the boat and set the timing.

 

[acuraguy81]

Re: Hard start and rough idle

PS the boats runs great after I get it off idle will run 45mph at 4200rpm very well with a 19p prop.

 

[acuraguy81]

Re: Hard start and rough idle

hmmm

 

[cr2k]

Re: Hard start and rough idle

Rebuild the Holley. Most likely cause of what you are describing is a blown power valve. If you can find one of the shielded power valves in the right range they are more durable.

 

[jtybt]

Re: Hard start and rough idle

If it seems like a fuel related issue, the first thing is to check or replace the fuel/water separator. Make sure the choke is working properly and re-check the firing order.

 

[jtmarten]

Re: Hard start and rough idle

If its been sitting all winter, try running some Techron. It may clean the partially clogged passages. Otherwise rebuild it, Holley's are painfully simple to work on, even a caveman could do it.

 

[lonemust]

Re: Hard start and rough idle

You can get a backfire protection valve to put in the HOLLEY to prevent the powervalve from being ruptured if the motor backfires for some reason. Costs about $12 at most auto stores or preformance shops. I agree HOLLEY's are good carbs but have power valve blow out problems. Slightest hiccup from engine can or will blow the valve. Engine will run just use excess fuel

 

[dannyual767]

Re: Hard start and rough idle

I think that you've got a dirty carb that needs cleaned.

Some are suggesting that you've got a blown power valve. I'm not sure if I agree with that but you're going to need to take the carb apart to replace it anyway so you'll be cleaning the whole carb.

If you do indeed have a blown power valve, you'll be running rich and your plugs will probably be very dark. Pull them and check.

 

[acuraguy81]

Re: Hard start and rough idle

Any tips how to get er clean before i get it rebuilt.

PS gonna take the carb to a local shop who knows holly cabs and order this rebuild kit asap. But till then any tips to get it running better?

 

[jtmarten]

Re: Hard start and rough idle

Disassemble, spray passages with gumout, use a fine wire to clear passages if needed, blow out passages with compresssed air.

Use a bottle of Techron until you get the carb off for rebuild.

 

[acuraguy81]

Re: Hard start and rough idle

Techron where can I get that? never heard of it. What am I disassembling the whole carb, or just the breather not sure what passages either the 2 main barrels or more than that?

Thanks

 

[jtmarten]

Re: Hard start and rough idle

You can get Techron at most any auto parts stores, WalMart, etc.

 

[floater180]

Re: Hard start and rough idle

Its Techron made by Chevron. Its in a black rounded bottle with blue labels. it works great. Did you ever check to make sure you're getting spark on all cylinders? Check the distributor cap and look under it to see if all contacts are still there.

 

[acuraguy81]

Re: Hard start and rough idle

the boat has had a full tune up. How do I use the techron put it in the tank or soak the carb in it or pour it down the barells? PS i did put some sea foam through the carb and in th fuel