1988 omc 5.0l cobra i/o

[ggundersen3]

My 1988 Bayliner 195 has an OMC 5.0L Cobra I/O. It runs well, shifts well, accelerates well but is very hard to start the first time I start it when it's been not run for several days or a week. I have to prime it with the throttle 15-20 times before it will start, once it starts it will restart perfect the rest of the boating day. I'm thinking there is a check valve somewhere in the fuel line to the carb that isn't hold pressure and all the gas is running back to the gas tank and that it takes 15-20 primes to get the fuel up there. Am I correct? If so how do I repair that? Or am I wrong and it's something else?

 

[MikDee]

Re: 1988 omc 5.0l cobra i/o

Well, it could be a bad float, or setting, in the carb. or, a leaky carb bowl, causing your fuel to leak down into the manifold, and, or, it could be bad, clogged, or leaky antisiphon check valve located either in the fuel line or tank? You do have an antisiphon valve in there somewhere right? It's the LAW. Blow back into the fuel line, just before the fuel pump, and it should vibrate, or rattle a bit, against the spring loaded check ball.

 

[bruceb58]

Re: 1988 omc 5.0l cobra i/o

Look into the throat of the carb and have someone pump the throttle. Don't do this while you are cranking the engine. Are you getting a healthy spray of fuel from the accelerator pump?

 

[Lou C]

Re: 1988 omc 5.0l cobra i/o

The main things here are:

Does the choke close all the way? Does the choke unloaded pull the choke open a fraction after it starts?
Pull off the flame arrestor and have some one watch when you try to start it.
Keep in mind that yearly cleaning of the choke plate and linkage was a part of a standard time up in the day of carbureted engines. What carb do you have, 2 bbl or 4 bbl ?
Also some Rochester Quadrajets had plugs in the bottom of the fuel bowl that can leak down fuel causing the same problem.

 

[Chrisbaughman]

Is a 5.0 cobra I/O a 302 or a 305? Me and my buddies have been debating back and forth and I'd like to be able to tell them exactly. Plus it definitely helps with the buying parts piece of the pie.

 

[bruceb58]

Distributor toward the stern...GM.

 

[Lou C]

GM 5.0 = 305 cu in
Ford 5.0 = 302 cu in
Anyone who bets against that will lose...

 

[GA_Boater]

This thread is from early 2014. Back to sleep.

 

[southkogs]

305 for the win!

... and a year old thread. Welcome aboard Chris: if you've not read our forum rules, please take a moment to do that. We ask that you don't post in a thread over 90days old unless you're the original poster.