1994 5.0 cobra dies at low idle

[Andan]

I have just bought a 1994 Four Winns Horizon with the 5.0 cobra engine. It starts and runs with a little throttle in neutral. It will warm up fine, but it will die before you can put it in gear. I can then start it and get it in gear quickly and is fine. Out on the open water it runs great at higher throttle. What all do i need to check before adjusting on the carb?

 

[HT32BSX115]

I have just bought a 1994 Four Winns Horizon with the 5.0 cobra engine. It starts and runs with a little throttle in neutral. It will warm up fine, but it will die before you can put it in gear. I can then start it and get it in gear quickly and is fine. Out on the open water it runs great at higher throttle. What all do i need to check before adjusting on the carb?

Welcome aboard!

Well, first of all, it will help all of us if you post your model number. Your engine drive package could be one of the following:


502ACPMDA 1994
502AGPMDA 1994
50FACPMDA 1994
50FACPMDM 1994
50FAGPMDA 1994
50FAGPMDM 1994

502APLJVB 1993
502APRJVB 1993
502BPRJVB 1993
50FAPLJVB 1993
50FAPLJVN 1993
50FAPRJVB 1993
50FAPRJVN 1993

Regards,


Rick

 

[kenny nunez]

If you have a Holley carberator on your engine it is a good chance that the gaskets between the metering block and throttle body have shrunk and several of the small fuel and air bleed passages are not sealed. The newer gaskets are blue in color and can be purchased at several auto stores. The small air idle screws should be 1.5 turns from lightly seated which should give a smooth idle.

 

[Andan]

The model number is 502ACPMDA. I've taken the boat out three more times and the low idle will hang in there for about 30 seconds now before it dies.

 

[HT32BSX115]

The model number is 502ACPMDA. I've taken the boat out three more times and the low idle will hang in there for about 30 seconds now before it dies.

It appears that your engine could have either a 2bbl or 4 bbl Holley carburetor (if it is unmodified in the last 21 years)

You can view parts diagrams and numbers at http://epc.brp.com/

• 3854107 Volvo Penta
• 18-7245 Sierra Marine
• 9-37630 Mallory Marine

iBoats actually sells Sierra parts at competitive prices. (and you can also get Sierra at NAPA)

Before you jump right in and start tearing your carburetor apart though you should probably ensure that you have good fresh fuel in the tank, new fuel filters and good clean sparkplugs, dist cap and wires.

Since your engine and drive are essentially a Volvo SX, all the part numbers are Volvo (beginning with a "3") you can get them from your favorite Volvo Penta dealer but be ready for some sticker shock

If it's a 2-bbl, you can order the carb repair kit right here! http://www.iboats.com/Carburetor-Kit-18-7244-Sierra/dm/view_id.172041

4-bbl http://www.iboats.com/Carburetor-Kit-18-7245-Sierra/dm/view_id.172042

Before you rebuild the carb though, you should probably try adjusting it along with the throttle/carb cable. There's a rather specific procedure to do it.
It's not hard and it really would help to have an OEM service manual. (NOT Seloc/Clymer although they're pretty good for starting your woodstove)

You can also go here: http://boatinfo.no/lib/omc/manuals/1986-1998omcmanual.html#/0 but you need a fast internet connection and a BIG display!

Regards,


Rick

 

[Andan]

I will definitely change the wires, plugs, and filters. What octane fuel should I be using? Just been putting 87 in it so far and went through about 40 gallon so far. The boat runs great tubing and cruising from above idle to full speed. Thanks for the info I really appreciate it!

 

[HT32BSX115]

I will definitely change the wires, plugs, and filters. What octane fuel should I be using? Just been putting 87 in it so far and went through about 40 gallon so far. The boat runs great tubing and cruising from above idle to full speed. Thanks for the info I really appreciate it!

The owners manual will probably indicate using 87 octane (regular)

OMC in the past did actually have 2 different ignition timing settings dependent on whether using premium or regular fuel. Most marine engines are set up for 87 octane regular since higher grades may not be available at most lakes

 

[Andan]

I changed all the plugs and ohm tested all the wires and they are good. I changed the fuel filter and screwed in the low idle jets all the way and took them out 1 1/2 turns. I had some slack in the throttle cable and was able to adjust it out of it. It now purrs like a cat at 500rpm at idle and no issues dying. I need to get a better prop without wear on it now and I believe I will be in good shape. Thanks for the help.

 

[HT32BSX115]

Good job! Everything will be right if you can turn at the top of recommended max rpm range at WOT (wide open throttle)