gm 305 exhaust tube?

[sarantis]

Sea-Ray 220cc/gm305 1978-82(MCM228)
Almost everything checked,still i can't find why i can't ran over 3000RPM.Three things left to check
1)the old high tension leads
2)the valves(i've adjusted them properly but i don't know if they work properly)
3)i've replaced the exhaust tube with bellows (i've read the relative threads about them) but my dealer had told me that everybody uses the bellows
Fuel delivery is good.
Which of them is more possible to be responsible for my problem?
(The sparks are getting black and oiled too fast.)
Thanks in advance for any replies

 

[Haut Medoc]

Re: gm 305 exhaust tube?

Fouled plugs is usually too rich mix......
Too cold plug range......
I thought you put new ignition wires on it?.......​

 

[ringmaster]

Re: gm 305 exhaust tube?

my cousins boat did the same thing its a sea ray 195 305 engine when i took it in to get the carb rebuilt the guy adjusted the points and timed it. no it goes to 4000 easily.

 

[sarantis]

Re: gm 305 exhaust tube?

Excuse me ,so many years i study english still i 'm not used to the way you talk.Will you please explain me better?
What does "too cold plugs range" mean?
The last sentence is a suggestion to replace the wires?

 

[sarantis]

Re: gm 305 exhaust tube?

Sorry Haut now i remembered that the 3rd sentence comes from a previous thread of mine.But do you think this may be the problem?

 

[Haut Medoc]

Re: gm 305 exhaust tube?

Excuse me ,so many years i study english still i 'm not used to the way you talk.Will you please explain me better?
What does "too cold plugs range" mean?
Some plugs fire colder than others, are you sure you have the right plugs?.....
The last sentence is a suggestion to replace the wires?

If you haven't done so, then yes & make sure they are in the proper position, of course......
As far as exhaust tube vs. bellows, there should be no difference with respect to performance......

 

[rebars1]

Re: gm 305 exhaust tube?

Is this a new development? Did you used to be able to get more rpms and now you can't? Maybe the throttle linkage does not open the carburator all the way.

 

[sarantis]

Re: gm 305 exhaust tube?

Well,i didn't want to confuse you so i didn't meant the following,
The problem maybe after the rebuilt of the carb by one which is supposed to be the best.I noticed that when i push the rod of the vacuum diaphragm that opens the air valves then the boat goes to over 4000RPM.The "best" here says that the vacuum may not work properly by some other reason,for example big propeller.I told him i haven't changed it and he sent me another carb that it performs only 100-200 rpm more than mine.That second carb doesn't go the boat faster neither when opening by hand the air valves nor by droping by hand some gas over the carb and the "best"here replies that it's not possible two faulty carbs.That's why i'm so confused and i can't distinguish if the problem is the carb,bad combustion(tommorow i'll replace the wires)or bad exhaust.(new risers,manifolds,timing and dwell correct).
Haut thank you for your explanation.

 

[Haut Medoc]

Re: gm 305 exhaust tube?

Is this 4000 that you are getting in the water in gear?.....​

 

[sarantis]

Re: gm 305 exhaust tube?

Yes the 4000 is in water in gear.Out of gear the engine performs perfect if we except a litle play at the idle rpm.
Anyway today i put new wires but exactly the same problem.It hesitates to go over 3000rpm and the sound at this point changes like it can't breath well.So i return to the first assumption and i'm asking?Is it possible for a Rochester 4bl to pull the vacuum rod and thus open the air valves manually and the boat sounds good and goes to 4000rps however the problem not to be the carb but something else? for example a friend's assumption is that maybe because i adjusted the valves as the manual describes,the previous owner had adjusted them just to the point they don't rattle because possibly of low tension spring they couldn't close right and so i created the problem.
I'm very much forward to hearing your opinions,

 

[Haut Medoc]

Re: gm 305 exhaust tube?

I really doubt it is a valve issue......
You say that it idles unevenly?......
Have you checked vacuum with a gauge?......
Rochesters have a vacuum secondary & there is a reason they are not opening......
Oh, & have you checked the distributer shaft (rotor) for 'wobble'?...
Have you cleaned the flame arrestor or tried running without it?......
Make sure the engine cover is open when you do that, btw......
I'd check vacuum before anything else......​

 

[sarantis]

Re: gm 305 exhaust tube?

this is what i was trying to avoid!I don't have the gauge and i don't know how this process is done.Will you be so helpfull?

 

[sarantis]

Re: gm 305 exhaust tube?

Do you mean the vacuum of the intake manifold?In fact i forgot to mention that i had changed the gaskets below it but i ve tigthened the manifold as firmly as possible.i can see very slight moisture at edges at its center sides but even the car mechanic didn't pay attention to it.He also examined the distibutor rotor by hand for side play and it looked good.Flame arrestor is also good and i've checked without it.

 

[Haut Medoc]

Re: gm 305 exhaust tube?

You should be able to get a vacuum gauge at any auto parts store, even in Europe I would think.....
Read this......
http://www.theautoist.com/vacuum_guage.htm
There should be a plug on your manifold to attach the gauge......​

 

[Haut Medoc]

Re: gm 305 exhaust tube?

& this......
http://www.centuryperformance.com/vacuum.asp
.....​

 

[sarantis]

Re: gm 305 exhaust tube?

Thank you Haut but when reading the instructions i remembered that when i fully turn in the two idles mixtures the engine doesn't go off.In this case the link says that i run reach.So in this case do i have to look only to the carb?

 

[Haut Medoc]

Re: gm 305 exhaust tube?

Do the test, it will tell you alot.....
Then worry about fine tuning the carb......
You cannot fine tune the carb if you have a vacuum leak, late timing, worn valve guides, etc.....
You have the special Rochester tool for the mixture screws, I presume?.....​