99 4.3 LH popping at high rpm

[Dennis197SD]

Hey all,

Recently did an engine upgrade on my bayliner 197sd. I bought a donor boat with a good running v6. I replaced all plugs, wires, cap etc and made sure everything ran great before i did the swap... Basically all plug and play. After getting the boat on the water and getting up to 4400+ rpm it begins backfiring and popping thru the carb... Re timed it at this point which helped but didn't solve the issue. Recently went on the water and just adjusted distributor and the air fuel mixture to get the best result without using the gun and got it so it doesn't do it until around 5k -5200

rpm+(which is beyond operating range) but when i put the gun on it it's way off time The motor runs great otherwise.... No misses or anything abnormal other than this. Any help would be appreciated

serial# L359536

 

[alldodge]

The SN is showing TBV, are you putting the distributor in base timing mode to set?

Do you know if the tachometer is accurate?

 

[Dennis197SD]

It is? Everything pointed to tb4 for me so i didn't... It also called for the purple and white wire to be grounded which i don't have. White/red and white/green is what i have

 

[Dennis197SD]

And. Yes. The tach is accurate.

 

[Dennis197SD]

Just hooked the gun up in base mode..only about 5 degrees difference. Its still about an inch off. Would the knock sensor cause this if its detecting a knock at high rpm?

 

[alldodge]

Post a pic of your ignition module should look like item 9 mounted on a plate

https://www.mercruiserparts.com/bam/subassembly/31480/2694/50

Double check your firing order

 

[Dennis197SD]

Can't seem to upload the pics. I'll have to do it from a cpu

 

[Dennis197SD]

Can't seem to upload the pics. I'll have to do it from a cpu

 

[Dennis197SD]

I did notice my distributor is not in the same position as the schematic. Mine is about 90 degrees counter clockwise. Not sure how close that should be to actual

 

[alldodge]

Yes, that is a TBV module, the purple/white wire should be there somewhere

The position of the distributor is of no concern so ling as firing order is correct

 

[Dennis197SD]

I did end up finding the purple/white wire. I originally thought they were talking about wires of the distributor. I hooked up gun in base mode and it's still like an inch off