I have an unusual timing issue, I found a post with a very similar issue on another site, someone said it was normal, but it's a new issue and does not seem normal. The suggested resolution is replace the distro with an MSD. (http://www.marineengine.com/boat-forum/showthread.php?23206-1987-Mercruiser-454-Timing-Issue)
I'm working on a 1982 merc 330TR, the engine is upgraded to a 370 4 bolt main. It's the second rebuild in 2 years (oil issues on the last one), I did not have this issue last year but I did replace the distro and the pickup this year, the original was really worn and had the old microswitch pickup, unfortunately that pickup broke and I converted that distro into an oil pump priming tool so I cannot try the old setup. I believe the ign amplifier on the riser is a v8-22 (no stampings but 10 deg base gets me 32 total at 3700+)
So here is the issue as in the other post, I can set the idle timing to 10 deg at 800 ish rpm, however when I adjust the idle down or put it in gear and the rpm drops to around 700 ish, the timing goes to 0 deg, when the RPMs come up, just over 700 ish the timing jumps back to 10 and the RPMs jump up to 900 to 1000, This happens every time, regardless of how slowly I bring the rpms up, at a certain point just over 700 rpm the timing and RPMs jump. I tried setting the base to 12 deg at 800, when it falls off at 700ish, It still goes to 0.
If I set the timing to 10 deg keeping it under 700 RPM, it still jumps once the RPM picks up, but this causes my total timing to be in the 40's, which is bad.
Any suggestions or just replace it with the MSD? I hate to keep throwing money at this without a determined cause because this has worked properly before.
--clawless
I'm working on a 1982 merc 330TR, the engine is upgraded to a 370 4 bolt main. It's the second rebuild in 2 years (oil issues on the last one), I did not have this issue last year but I did replace the distro and the pickup this year, the original was really worn and had the old microswitch pickup, unfortunately that pickup broke and I converted that distro into an oil pump priming tool so I cannot try the old setup. I believe the ign amplifier on the riser is a v8-22 (no stampings but 10 deg base gets me 32 total at 3700+)
So here is the issue as in the other post, I can set the idle timing to 10 deg at 800 ish rpm, however when I adjust the idle down or put it in gear and the rpm drops to around 700 ish, the timing goes to 0 deg, when the RPMs come up, just over 700 ish the timing jumps back to 10 and the RPMs jump up to 900 to 1000, This happens every time, regardless of how slowly I bring the rpms up, at a certain point just over 700 rpm the timing and RPMs jump. I tried setting the base to 12 deg at 800, when it falls off at 700ish, It still goes to 0.
If I set the timing to 10 deg keeping it under 700 RPM, it still jumps once the RPM picks up, but this causes my total timing to be in the 40's, which is bad.
Any suggestions or just replace it with the MSD? I hate to keep throwing money at this without a determined cause because this has worked properly before.
--clawless
