How would a spun hub on a test wheel affect the timing adjustment?

[RoGun_Mako171]

I bought a test wheel on eBay for my Johnson 88 spl and tried using it on the lake to set my timing, but found the rpms would spike once they hit 3500 and felt something was wrong. I put on my regular prop to enjoy the rest of the day. Getting back to setting the timing, I marked the hub on the test wheel so I could see if it is spinning and used a tank I built from a 250 gallon IBC water tank. While brining it up to full throttle, I was not getting the spike I was on the lake and continued to set the timing.

After completing the work, I found that the hub is actually spinning because the marks on the hub and hub body no longer line up. I'm thinking it just wasn't spinning as much in the tank because it is not pushing the weight of the boat. Now my question... is my timing adjustment accurate or did I possibly advance it too far because of the spun hub?

 

[jimmbo]

Timing on these engines does not advance as Rpms climb. It is the opposite, Rpms climb as the timing is advanced to the max advance. Max spark advance can actually be set at cranking speed on most of these engines

 

[boobie]

Minus 4 *…..

 

[jimmbo]

Other systems electronically retarded the timing as the Rpms increase, my I6 was like that.

 

[RoGun_Mako171]

I've read a procedure on another site that describes how to set the max spark advance minus 4 degrees at cranking speed, but was concerned it was only an approximation. It would go something like this on the Johnson 88:
1. Hook up a flusher so you don't destroy the impeller
2. Pull the plugs and set up a spark tester on #1, ground out other plug wires
3. Put it in full throttle in neutral lockout
4. Hook up timing light to #1 plug wire
5. Crank the engine and set the max spark advance to 24 degrees (28*-4*)

Does that sum up the procedure?

 

[Tim Frank]

Why do you need to adjust the timing?

 

[RoGun_Mako171]

It's part of the link and synch procedure. I'm doing a tune up on my engine to get the optimal performance and want to assure it is properly adjusted. Only getting ~4400rpm at WOT with the WOT stop and carbs properly adjusted and cleaned and tightened, new fuel lines and fuel filter with a 13.25 x 17P aluminum prop and no VRO. The max advance before starting adjustments with the test wheel was between 23 and 24 degrees, so it seems like it was way off and needs to be properly adjusted.

 

[racerone]

Timing on these motors is fixed for the life of the motor.----Requires no owner maintenance.--------What are the compression readings ?----Does spark jump a gap of 7/16" on all leads, yes or no ?

 

[RoGun_Mako171]

After double checking with the Joe Reeves static timing method, I saw the max spark advance I set with the test wheel was spot on (24 degrees with the Joe Reeves method, 28 degrees with test wheel at WOT in a tank). When on the lake this past weekend, I got the RPMs up to 4700 at WOT, so I did see an improvement.

Compression is #1:125psi, #2:115psi, #3:125psi, #4:110psi. I did replace the head gasket on the port side last month, previous compression on #2 and #4 was 105psi.

Spark looks good on all leads, getting 7/16" gap jump and hearing a snap.