Timing Question for OMC 3.0

[carhopper]

Hey guys, I have an 18' Caravelle with an OMC 3.0 with cobra outdrive. I've noticed the last few times I've taken the boat out that the power is diminishing. It's never had enough power in my opinion since I bought it last year. I thought it was maybe a dirty bottom, fuel filter, plugs, etc but all were fine. Then I decided to check the timing today and it was set to about 3 degrees BTDC. From what I read on a tech article my engine should be set at 10 BTDC. I followed the procedure and advanced the timing about 5 degrees to 8 degrees to start off and wow what a difference. My hole shot was substantially improved.

Before I go and advance it to 10, I wanted to check with you guys to be sure 10 is correct, and also to ask how far I can advance the timing if I always run 93 octane?

 

[mkast]

Re: Timing Question for OMC 3.0

10 degrees BTDC, even if you use 100LL aviation fuel.

 

[sea wolf]

Re: Timing Question for OMC 3.0

Why run 93 octane? It's not neccesary.

 

[carhopper]

Re: Timing Question for OMC 3.0

Thanks for the confirmation on the 10BTDC. I run 89 octane as the engine prescribes, I was just asking about 93. I thought that I could advance the timing a bit for better performance and run 93 to prevent detonation. I'll take mkast's advice and keep it at 10BTDC. Thanks.

 

[carhopper]

Re: Timing Question for OMC 3.0

In fear of hurting my engine I download the maintenance manual. For a 1993 OMC 3.0 the timing should be adjusted to 0 BTDC with the shunt installed. I don't have a shunt, but as I read the procedure the final step says "11. Restart the engine. With the timing light still connected and the engine running at 1000 rpm, check that the timing advanced to 15 BTDC on all 1991-94 engines. Re-adjust as necessary by rotating the distributor." Why even do the first steps if you know you're not 180 degrees out and your dwell is working, why not just do the final step in a pinch. This was easy for me because my timing light has a 0-60 degree offset. I just set the offset for 15 degrees, and adjusted the mark for zero at 1,000 RPM. It runs great with no ping at WOT.