forgetg

I have a pair of 1992 525SC's that have been rebuilt but have been sitting for a few year, I'm putting in new plugs and wires and have got them cranked up and sound really good, I do want to check the timing.. my merCruiser service manual #3 says that I should be at 19deg BTDC with firepower ignition at 1500 RPM and my max timing advance 35 deg BTDC at 4500rpm..do these numbers sound right..with these numbers I have a MAC tl300, I hook up to # 1 cyl and set to 1500 RPM and set the dial to 19deg on the mac and my indicator on my timing tab should read 0..correct I just need to verify before any adjustment
Thanks in advance

ezstriper

I have a friend with a pair of these as well, just redid the engines last year, stock rebuild except for roller cam upgrade, found the boat works best with the dist. locked(no advance) and 28 deg timing...the 28 at idle helps the low speed drive ability tons and we have found no performance gains running any more timing...

Unlimited jd

iTrader: (5)

May not get any more performance but I'd be willing to bet his egt's drop a few hundred degrees adding 2-3*

Old Navy

My 1995 525sc had retarded timing when I got it because the mechanic at the marina was smarter than the factory. It ALSO had +50% leakdown thru the exhaust valves. I set the timing to 35 deg total with new heads and it has been running great for 8 years.

Griff

The total advance of 35* at 4500rpms is correct.
I cannot remeber the exact specs and advance curve for the Firepower Ignition. I had a TB IV on my 525SC. and I don't have my Merc 525SC manual anymore.
I would just set it to 35* at 4500rpms and let the rest fall where it may.

If the manual says that it has 16* of total advance, then setting it at 19* base timing is fine. I would set it with it running at less than a 1000rpms though.
Then verify the total timing by setting the dial to 35* and reving the engine up beyond 4500rpms.

forgetg

Thanks for the posts..these are scans from the manual...odd that the specs say 19deg at idle and 35deg at 4500rpm and the cure says 18deg at 1500rpm and 34deg at 4500rpm both scans are from the same Mercruiser Hi-Performance Series Service manual #3

[ATTACH=CONFIG]507088[/ATTACH][ATTACH=CONFIG]507089[/ATTACH]

MILD THUNDER

iTrader: (3)

Timing a engine for power is not the goal. Timing it for proper combustion is. Too little timing brings the EGT's up to a dangerous level. Too much timing and preignition happens. Mercury knew what they were doing. Stick with their recommendations. Retarding the total timing 7degrees from factory spec will more than likely cause premature exhaust valve issues.

Griff

1* won't really make any difference.
Set base timing at 18-19* and then rev engine to 4500rpms + to verify that timing with full advance is 34-35*
Timing at full advance is what is important.

I had a TB IV and ran mine with 35* and almost 8#'s of boost. Never had an issue.