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Carburated 4.3L tune up questions???
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Author:  Matt2000horizon180 [ Mon May 31, 2010 5:43 am ]
Post subject:  Carburated 4.3L tune up questions???
My boat was not staying running until warmed so I tried and completed the most of the tune up items in the Seloc manual with my Dad who worked on carburated engines for years. (Previously replaced the electric choke and spark plugs, checked all wires and gum out carb and fuel filter. New water sepperator and end of last season)

Couple things were confusing so I was hoping the forum could explain.

1. Timing. Seloc call for the timing to be set on my 2000 4.3 GL to be set at 6 DEG BTDC. We hooked up a timing light to #1 cyliner (Non-drivers side towards front of boat based on diagram which showed the cyliners and distributor) The fixed point on the engine was a single V-notch which was previously painted, and the line on the fly wheel was a single groove machined into the fly wheel which was also previosly painted.

We could not get the timing to line up with these two points. Rotating the distributor to try to get these to line up stalled the engine. We ended up making a minor adustment in the opposite direction which made seemed to make the engine run the smoothest.

Any comments on why the V block and the groove on the fly wheel could not line up. It is probablyoff by 2-3 inches which must be around 20 degrees??


2. Idle mixture.

My dad borrowed a hand held tach since Seloc said to not use the boat tach. This unit has positive and negative clips which we could not figure out how to connect. We followed the manual and and adjusted the idle mixture screws for best smooth performance at the lowest idle. Did not need to use the idle "speed" screw so it seems like it is good (not lean or rich)

The boat is running great now but would like to understand better so next year I can do this in the garage before wasting a month of bad performance.

Thanks.
Author:  Aussie_Horizon_190 [ Mon May 31, 2010 6:29 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Hi Matt.

1. You might find the single line on the balancer is TDC (top dead center) or 0 degrees, although if you did time to this is would still idle OK. I'm wondering if the outer balancer ring has moved on the inner... sometimes happens. What you need to do is pull spark plug #1 and get the piston up to the very top (TDC), and check or mark this (TDC) on your balancer to confirm if this is the case or not. Also draw a line with a pen across the outer and inner rings to see if they are still moving... If this is the case, you may want to replace the balancer as I have seen the outer ring come completely off with pretty ugly consequences! You can get either a new or a refurbed balancer

2. Sounds like your Dad has everything under control to me (must be an old hot rodder as well :D ). Carb adjust is exactly as I would have done it. Why does it need adjusting? Gaskets dry out, crap accumulates in the tiny passsages, fuel quality changes, things deteriorate, etc. Eventually when you can't adjust it enough, you'll need to get a carb rebuild, but until then don't worry about it - just get out there and enjoy it!
Author:  Matt2000horizon180 [ Mon May 31, 2010 7:10 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Thanks Alec. My guess on the carb was by adjusting the mixture screw all the way in, then all the way out as well as the gumout directly in the fuel line, little clogs were cleared out. I did get a little "dieseling" today where the engine tried to keep running for 3-4 seconds after key off. Had this before with lower octane gas but have premium in it now.

I'll stop my local marina that did my winterizing last year and ask a few questions. I buy my parts there so they are pretty good about sharing info.
Author:  Aussie_Horizon_190 [ Mon May 31, 2010 11:07 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Hmmm... dieseling is generally low octane fuel, although if the timing was way out it could do it as well. I know because mine does it all the time with the crap fuel we get in Australia - even premium 98 octane!! :D

Maybe just check the TDC mark on the balancer is accurate then check the timing is 6 before TDC one more time. If thats OK, then it just the fuel...
Author:  gregs [ Wed Jun 02, 2010 2:19 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Idle speed too high will also cause run on.
My old VP 3.0L with electric choke came open way too soon before the engine was warm enough to run properly by itself.
Some engines require a different timing procedure than what we are used to with an auto engine.

Greg
Author:  The Kid [ Thu Jun 03, 2010 11:06 am ]
Post subject:  Re: Carburated 4.3L tune up questions???
If your distributor cap has two plug cutouts in it with one plug being used and the other not then your timing problem is that you need to put the engine in base timing. You need a shunt connected to the other plug and you will be able to adjust the timing. It can not be done without this!!
Author:  Matt2000horizon180 [ Fri Jun 04, 2010 7:06 am ]
Post subject:  Re: Carburated 4.3L tune up questions???
Hmm. My distributor does have 2 connector hubs. The non-used is covered with a soft plastic pug cover. Are you saying I need to use the other connector plug to set the timing then back to the "current" plug for running?
Author:  The Kid [ Fri Jun 04, 2010 12:51 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
No the one that has the rubber cover.. that is where you need to connect the shunt to and then the motor will be in base timing.
Author:  Matt2000horizon180 [ Fri Jun 04, 2010 4:18 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Sorry but what is the shunt?
Author:  gregs [ Fri Jun 04, 2010 7:48 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
The link below is from Dons at iboats. There are Mercury factory manuals there. I have cut and pasted the timing procedure. There is no manual like factory manual.

Greg


http://forums.iboats.com/showthread.php ... %201693398

SERVICE MANUAL NUMBER 25 THUNDERBOLT V IGNITION SYSTEM
90-861328--1 NOVEMBER 1999 Page 4B-5
Timing and Idle Adjustment Procedures
Setting Base Ignition Timing
1. Connect timing light (91-99379 or similar) to No. 1 spark plug wire. Connect power
supply leads, if applicable, on light to 12 volt battery.
2. Connect a shop tachometer to engine.
3. Using a jumper wire, connect the ignition system timing lead (PUR/WHT wire) to a good
engine ground (–). This locks the ignition module into the Base Timing Mode.
NOTE: Before starting engine make sure the timing tab and marks on damper are clean.
Chalk or white paint on timing marks may help visibility.
4. Start engine and run at normal idle speed. Allow engine to reach normal operating
temperature.
5. Aim timing light at timing tab, located on the timing gear cover and crankshaft torsional
damper.
6. If adjustment is required, adjust timing by loosening distributor clamp and rotating
distributor body as required until timing mark on damper or pulley lines up with the mark
on tab specified in “Specifications.” Tighten clamp and recheck location of timing mark.
7. Make sure that the distributor has been tightened. Remove the jumper wire from the
timing terminal.
8. Remove jumper wire between the timing lead (PUR/WHT wire) and ground (–).
IMPORTANT: Be sure to disconnect the jumper wire from between the ignition system
timing lead and ground (–) before attempting to resume normal operations. If the
jumper wire is left in place, the ignition module will operate in the Base Timing Mode.
This means that the additional timing advance features would not function.
9. Stop engine and remove timing light.
Adjusting Idle Mixture
The procedure for adjusting carburetor idle mixture can be found in the appropriate engine
service manual. This procedure also requires that the ignition module be locked in the “Base
Timing Mode.”
IMPORTANT: In order to properly set idle mixture, the ignition module MUST BE
locked in the Base Timing Mode. This is necessary because of the Idle Speed Control
feature that exists in the ignition module. See information on the previous pages
about this feature.
To adjust the idle mixture screw correctly, the throttle plates must be nearly closed. Please
do the following:
1. Disconnect throttle cable.
2. Set idle speed (rpm) screw so engine idles at 550-600 rpm in neutral gear.
3. Adjust idle mixture screw.
4. Reset the idle speed screw until engine idles at its recommended rpm.
5. Adjust and connect throttle cable.
Author:  Matt2000horizon180 [ Sun Jun 06, 2010 6:26 am ]
Post subject:  Re: Carburated 4.3L tune up questions???
Thanks everyone. I ordered the shunt tool on-line yesterday for $17. Volvo p/n 885163. Should be here for next weekend.
Author:  gregs [ Mon Jun 07, 2010 8:11 am ]
Post subject:  Re: Carburated 4.3L tune up questions???
Sorry, missed the fact that it was a 4.3GL.
Author:  Matt2000horizon180 [ Mon Jun 14, 2010 12:50 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Got the part and it worked like advertised. Boat was very close to being in time where is was originally so that was not my problem. But good to verify anyway.
Author:  gregs [ Mon Jun 14, 2010 1:24 pm ]
Post subject:  Re: Carburated 4.3L tune up questions???
Good show. Did you get a chance to check the idle speed?
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