Tuning up a 1999 VP 4.3GS have some questions

[AdamB]

Okay, before I get yelled at, I did check the stickys and the one link to a shared file location with timing isn't current. Anyhow, my engine is running rough, rich at idle, so I bought all new distributor cap, rotor, wires and plugs, plan on timing (I have the shunt) but can't find the correct timing. I see that the 4.3GL is 1?BTDC but is that the same as on the 4.3GS. I also have vacuum gauge so plan on checking the idle screws...Thanks in advance

 

[bnicov]

Include all the letters after tbe GL for your engine. They can be found on the engine tag on the circuit breaker box at the front if your engine.

 

[AdamB]

4.3GSPBYC I think it's kinda faded

 

[AdamB]

I know the GL is 195 hp and the GS is 205 hp and mine had 4 barrel Holley carb.

 

[AdamB]

Nobody?

 

[Bondo]

Ayuh,.... I donno,... I'd Guess the same as the other 4.3l,.....

Merc just changes the carb from a 2bbl. to a 4bbl. goin' from the lower hp to higher hp,....
Same tune up specs,.....

 

[AdamB]

Okay, so the old distributor cap was majorly corruded, same with rotor, the plugs were all fouled, so changed all that and wires, (parts from here too), mixture screws were way different from each other, 1 side 2.5 turns out, the other 2... hooked up vacuum gauge and now they're both around 1.25 turns out, no more rich fuel smell at idle. I put the timing shunt in and timed it, just left it as is until I take it for a ride... it is set at 5? BTDC. I run high test and I know the compression ratio is like 9.4:1 so... guell I'll get a service manual just to double check. I found the specs for the GL on youtube and it said 1?BTDC...

 

[AdamB]

put lots of dielectric grease on all that parts...thought Bondo would like that

 

[AdamB]

also just dialed in 5 on my advance timing light to get the mark on the balancer to line up with notch on the cover, so it might actually be 5?ATDC

 

[AdamB]

It's amazing how much better an engine runs with a good tune up. Much more smooth idle with no rich smell, gained couple hundred rpms on top end too!

 

[AdamB]

Just a side note for those with VP and Larson boats, I switched from a VP aluminum 21" prop to ballistic 23" prop to bleed off some upper Rpms. Wow the boat is like a different boat. The prop design really pushes boat up and out of the water. Result is high Rpms still but increased top speed too. I think my slip rate went down because my speed went way up.