Does my carb need to be rebuilt?

[SS194]

Hey guys, I've got a 76 Merc 5.0. Hooked up to the hose in my driveway, I can start it up easily and will idle all day long. But, put it in the water, and it's a whole different story.

Last season I had absolutely no problems. This year is a different story. I have a very difficult time keeping it running in the no wake zones.

It'll usually crank right up, but sometimes it will fire then quit. It also usually needs to be cleared out...sounds flooded.

Then putting it into gear is another challenge. It'll bog and run rough under a light load. A little throttle and it'll clear out. Once on plane it runs like a champ.

So, why is it loading up at idle? And again, it only seems to be under a load. Idle is set at about 950 no load...about 800 under a load (if it's not loading up)

Now, it's a Rochester 2 barrel. There are two little screws. I was told that while it was running and warmed up, turn one screw clockwise until the engine bogged down, then back it off. Do the same to the other. Well, I did that...I don't think it worked. Now while on plane, it seems to be running too lean. But those crews are the idle only, right?

What is the proper way to adjust this carb? How do you know when it needs to be rebuilt?

Thanks guys,
Steve

 

[Haut Medoc]

Re: Does my carb need to be rebuilt?

Ford 302 or GM 305?......
Have you checked cleaned fuel filters?.....​

 

[SS194]

Re: Does my carb need to be rebuilt?

Sorry, it's a Ford 302.

Yeah, that's brand new. I had to replace the old copper fuel line with a new rubber fuel line. The old copper one was corroded.

Other than that, nothing has changed from last year.

 

[Haut Medoc]

Re: Does my carb need to be rebuilt?

Your idle is too high for one thing.....
Should be 550-600 in water, in gear....
No more than 800 in neutral, max.....
When was the last full tuneup done?.....
Have you checked timing, dwell & verified tach?.....
How much crap came out of the water separater?......
Do you have the built in vacuum gauge in the dash?......​

 

[SS194]

Re: Does my carb need to be rebuilt?

Idle is high because I bumped it up trying to help it out...
Short story long, I bought the thing a year and a half ago from a very used boat dealer here locally. The original owner had a new engine installed by a marina. Found water in oil, got sick of it and sold it. I bought it for cheap and found one of the risers was bad. The engine didn't even have 10 hours on it. Hasn't let me down and doesn't burn a drop of oil.

I was under the impression that the carb was rebuilt, but I actually have no idea.

Haven't checked timing, but again, how is it that it ran like a top last year and this year it has an idle problem? I do know that I need to check it though.

Dwell time? What is that?

Verified tach? Now, but I'm interested as how to check that.

A lot of crap came out of the water separator. It looks like an internal seal was decaying inside of it. I obviously changed the separator to a new one.

No built in vacuum gauge. I know they are cheap and easy to install though.

Thanks for the questions. I hope these answers help you.

Steve

 

[Haut Medoc]

Re: Does my carb need to be rebuilt?

Idle is high because I bumped it up trying to help it out...
Short story long, I bought the thing a year and a half ago from a very used boat dealer here locally. The original owner had a new engine installed by a marina. Found water in oil, got sick of it and sold it. I bought it for cheap and found one of the risers was bad. The engine didn't even have 10 hours on it. Hasn't let me down and doesn't burn a drop of oil.

I was under the impression that the carb was rebuilt, but I actually have no idea.

Haven't checked timing, but again, how is it that it ran like a top last year and this year it has an idle problem? I do know that I need to check it though.

Dwell time? What is that?
On a points type system dwell is how long the points are closed....
They affect timing & vice versa...

Verified tach? Now, but I'm interested as how to check that.
They have timing lights that do that, you might want to invest in one...

A lot of crap came out of the water separator. It looks like an internal seal was decaying inside of it. I obviously changed the separator to a new one.
Well, that could've put crap into the idle circuit...

No built in vacuum gauge. I know they are cheap and easy to install though.

Thanks for the questions. I hope these answers help you.

Steve

The vacuum gauge is the best way to set those screws on the carb....
It can also tell you other things regarding your engine's overall health.....
It would not hurt to do a compression test either.....
All of the stuff I have been feeding you is so that you can see how healthy the engine is before you start throwing parts at it or fiddling with settings....
For instance high idle is not good for a Merc drive.....
You are gonna need to get the diagnostic stuff anyway if you want to do your own PM......
Hope this helps......

 

[SS194]

Re: Does my carb need to be rebuilt?

It does, thank you

 

[Bondo]

Re: Does my carb need to be rebuilt?

Idle is high because I bumped it up trying to help it out...
I was under the impression that the carb was rebuilt, but I actually have no idea.
A lot of crap came out of the water separator. It looks like an internal seal was decaying inside of it. I obviously changed the separator to a new one.

Ayuh,..........

You can Bet that atleast Some of that Crap made it to the Carb,......
Regardless of When the Carb may or may not have been Rebuilt is kinda Irrevelant......
It probably Needs it Again........
And,......... I'd change the Fuel Filter a few more times rather Soon as well...........
Bumping the Idle to get it to Run, will only turn your Outdrive to Broken Little Pieces..........
Alpha's like a Very Low idle......... Pre-Alphas are no better.......

Haven't checked timing, but again, how is it that it ran like a top last year and this year it has an idle problem? I do know that I need to check it though.

Dwell time? What is that?

Ayuh,........ You've got Points Ignition,...... They're rather Labor Intensive,.........
Haut can give you the Required Info,.......
He's got a motor Just like your's I believe.................

 

[SS194]

Re: Does my carb need to be rebuilt?

Thanks a lot.

I'll send Haut a message and see what he thinks.

Steve