Hi All, new member in need of some wisdom from those familiar with the M/C TB4 ignition system.
I have a 1991 Bayliner with a M/C 5.7/260HP engine with an Alpha Drive. I've owned it about one year now and last summer, before I splashed it, I put in new plugs, wires, cap, rotor and rebuilt the Q-jet carb. I also went through the outdrive. Since the first day on the water, it seemed like the boat was struggling to get on plane and couldn't make WOT. I only have about 20 hours on the boat since last summer, so today I figured I'd delve deeper into why the performance was lacking.
First I did a compression test and found that the engine was in pretty good condition, high comp was 175 and low comp was 155. I then checked to make sure I had WOT on the carb linkage and that too was OK. I then checked timing, as last year I simply set the timing at 8* and left it at that. So today I hooked up my shop tach and was going to check the timing from 650 RPM on through the scale and found that the 8* was there at 650, but the furthest it would advance was about 14*. At about 1200 RPM it was at 12* but going higher it stopped advancing just off the end of timing tab, or approximately 14*. At 3000 RPM it stayed in the same place. I believe this package is supposed to have about 22* in the module, so I was looking for somewhere around 30* total.
So my question is, do I need a new TB4 module, or is there some other test I can perform before I drop a pant load on a new module? Any assistance will be sincerely appreciated. BTW, sorry for the long first post.
Paul
I have a 1991 Bayliner with a M/C 5.7/260HP engine with an Alpha Drive. I've owned it about one year now and last summer, before I splashed it, I put in new plugs, wires, cap, rotor and rebuilt the Q-jet carb. I also went through the outdrive. Since the first day on the water, it seemed like the boat was struggling to get on plane and couldn't make WOT. I only have about 20 hours on the boat since last summer, so today I figured I'd delve deeper into why the performance was lacking.
First I did a compression test and found that the engine was in pretty good condition, high comp was 175 and low comp was 155. I then checked to make sure I had WOT on the carb linkage and that too was OK. I then checked timing, as last year I simply set the timing at 8* and left it at that. So today I hooked up my shop tach and was going to check the timing from 650 RPM on through the scale and found that the 8* was there at 650, but the furthest it would advance was about 14*. At about 1200 RPM it was at 12* but going higher it stopped advancing just off the end of timing tab, or approximately 14*. At 3000 RPM it stayed in the same place. I believe this package is supposed to have about 22* in the module, so I was looking for somewhere around 30* total.
So my question is, do I need a new TB4 module, or is there some other test I can perform before I drop a pant load on a new module? Any assistance will be sincerely appreciated. BTW, sorry for the long first post.
Paul
