350 Mag Still Bogging Down

[Mahoney]

Re: 350 Mag Still Bogging Down

Don't count your chickens yet, it could be other issues, but it sounds like you changed something that is directly related to symptoms you are experiencing.<br /><br />Good luck, lets hope that is it.

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

I didn't change the springs, just replaced with the same ones.....it ran the same way with the original springs.<br /><br />Just to bring you up to speed: I just bought the boat about a week ago......this is how it ran when I bought it. I did a complete tune-up and rebuilt the carb. I checked the compression: 140-170#. The guy I bought it from was not mechanically inclined at all.........<br /><br />I think we're on to something here.<br /><br />Thanks..........

 

[bigdaddyofhouse]

Re: 350 Mag Still Bogging Down

DAMN IT. HAVE YOU CHECKED YOUR VOLTAGE?

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

According to the voltmeter on the dash the alternator is working.

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

I changed the springs from the strongest to the weakest.....it had some affect but didn't cure the problem!!!!<br /><br />Tomorrow I am going to check the fuel pump pressure.<br /><br />Any other hints? How about the advance? Is it supposed to be a full advance by ~ 2200RPM's?

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

Any other ideas? Or are you guys giving up on me...............?

 

[Mahoney]

Re: 350 Mag Still Bogging Down

Do the barrells in the secondaries still look wet like they are getting too much gas after you bog?<br /><br />Pick up a volt meter as well and check the voltage at the battery before and after starting, don't trust the dash volt meter.<br /><br />If you continue to push through the bog, does it eventually get past the bog?

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

never passes the bog..........<br /><br />I have a voltmeter.....will check tonight

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

Now what? The fuel pump pressure is good (~6lbs)and the alternator is fine (14V after started).<br /><br />I am stumped. It must be the tuning of the carb, when the secondaries are opening and when the metering rods are moving up opening the primary jets.<br /><br />Anybody have any experience with tuning these carbs?

 

[Limited-Time]

Re: 350 Mag Still Bogging Down

FBT,<br /> What size and type of boat is the 350 in. Must be good sized to only be spinning a 15 pitch prop. There was a thd a while back similar problem, turned out the wrong ratio out drive was installed...you said the boat was new to you, do you have any history on it,.......just a thought.

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

its a 24' Grady White Offshore. Weights ~4000lbs.<br />I'm sure O/D ratio is correct.

 

[Mahoney]

Re: 350 Mag Still Bogging Down

can you adjust the secondaries and when they open on that carb? if so adjust them so they open later when you apply throttle and see what happens. <br /><br />Remember to only adjust one setting at a time, regardless of how much you think you want to tweak other things(trust me, I speak form experience) That way you can fine tune one adjustment rather than having to figure out which one it was that worked in the first place.<br /><br />Did you say that you ran the engine off a can of clean gas? Bypassing the fuel seperator and everything?

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

I will try adjusting the secondaries to open later.<br /><br />Yes, I ran the engine off a seperate tank bypassing the fuel seperator.<br /><br />I am totally stumped! I hope the problem is really the carb........

 

[Mahoney]

Re: 350 Mag Still Bogging Down

I had the same issues, and eventually solved it with a new carb, because I was impatient. Sounds like you verified about everything else, voltage, spark, timing, fuel composition, its gotta be the carb. If it was a rochester I could help you more, but I dont know anything about what you have, only to say something seems to be feeding it too much fuel when you engage the secondaries.

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

HOw much did you pay for the new carb?<br />Where did you get it?<br />Did you have to make any adjustments to it after you installed it?

 

[navigator336]

Re: 350 Mag Still Bogging Down

I had a very similar problem with a 350 with a 4150 Holley. I found the air bleeds for the emulsifing tubes blocked and partially blocked. Cleaning these out made the engine run perfect up to about 3900 (from about 2900). I ended up rebuilding the carb to completely fix the problem.

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

Can you describe the tube a little better? What are they for? As you know I have a Weber/Carter/Edlebrock.....

 

[FreeBeeTony]

Re: 350 Mag Still Bogging Down

Any other suggestions before I go down to the boat tonight?

 

[navigator336]

Re: 350 Mag Still Bogging Down

On the Holley, as you look into the throat and above the butterflies, there are two sets of four small vertical holes adjacent to the throat walls. One set for both the primaries and secondaries. Each set has two very small holes and two somewhat larger ones. The top of the hole is ever-so-slightly funnel shaped. If completely occluded, you might think they were just little passage plugs. As the engine is creating vacuum, air is drawn through these holes to pre-mix with the fuel being drawn through the jets. This emulsifies the fuel so that it better atomized as it comes through the venturies. It's kind of like foaming the fuel. You can clean them out using carb cleaner and a copper wire. Then you start the engine, take the spark arrestor off, rev the engine a little, and slap your hand down over the throat, then pull your hand off. THis almost kills the engine, but creates tremendous vacuum to suck the crud out.

 

[Aquadzac Captain]

Re: 350 Mag Still Bogging Down

Wow, you sound just like my weekend trying figure out WHY I can run great then bring it back to idle and add a little gas it boggs and dies. Then hard to start from there on. Did you ever find out if it was thermal issue or something else?