Setting the ignition timing, the "Joe Reeves Method" tested in real life

Hi fellow boaters, outboard engine mechanics,

I've purchased an older style Yamaha outboard in dire need of a revision. It's a two stroke three cylinder 70 HP long tail from 1989 (70ETLF), that has been converted to short tail (70 CES?), with a 17 pitch prop (5000 RPM ≈ 50 kmh). This because in Holland it's very hard to find 70 HP short tail, 60 HP short tails are somewhat easier to find, but still not in abundance). My RIB has a max of 70 HP (hence this engine) and my budget did not stretch to a four stroke. And I like doing a revision myself, so here I am.

After completing a total rebuild (new oversize pistons, bearings, seals, etc etc, all original Yamaha, carbs ultrasonically cleaned) I've started the 10 hour running-in process. This type still has the manual setting of the ignition stops, and the preferred methods (test prop or test bench) were not really an option due to budget constraints and lack of availability mid season. So I had to do it myself. I remembered my favorite outboard mechanic Stu from whom I've learned almost all my outboard mechanic skills (big shout out to you Stu! https://www.youtube.com/c/DangarStu) mentioning the "Joe Reeves Method" (http://www.marineengine.com/boat-forum/archive/index.php/t-454594.html) as alternative for hanging off your boat trying to point a timing gun at your growling outboard while facing backwards doing 50 kmh (31 mph).

Stu intends to test this method in practice, but hasn't come around to it just yet. And I couldn't find anyone else online who had tested this method, but did want to apply it. I guess that makes me the guinea pig for this method. So here I found myself this weekend, doing the hanging backwards-growling-gun-50 kmh-method. I did manage to time my engine correctly with the timing gun, so there is no more risk of overheating because of too much advanced ignition. But I would not recommend doing this with big waves. Step one finished.

Plan was to set the timing according to the manual in real life (done), and after that reverse-check the setting with the "Joe Reeves Method", so I will know it works from practice and will not have to jump through the hoops of real life testing again next time.

These things I still have to do:
- Take a picture of how I a was seated while testing in the wild, in case anyone wonders.
- Compression test (for reference).
- Test the engine again with the "Joe Reeves Method", so I can see if this method indeed comes up 4 degrees short of the max advanced degrees (20° for the 70ETLF).
- Post my other findings while testing.

I intend to post it within the next week.

As promised
About the testing.
I have done a compression test, and the results were OK, if not (yet) how I would like them to be (all 140+ PSI, little difference between the cylinders). This is probably due to the state of running in. From top to bottom: 138, 134, 129 PSI.
Ps 1: Any thoughts on the deviation from top to bottom (high to low)? The water flows from top (cool) to bottom (warm), maybe downwards more carbon deposition on the piston rings because of the excess running in oil (1:25)?
Ps 2: does anyone know if one has to use ring free after running in, because of these double quantities of oil used for 10 hours?

Will measure again later when running on regular oil mixture.

Here is a picture of me on dry land recreating the measuring pose used doing the timing while at (almost) full speed on the water. Wearing a life jacket and secured with a rope around my waist. The rope made sure I could not fall off the back of the boat.


During the real life testing on the water I at first thought the Joe Reeves Method didn’t work. I had set the timing using the procedure in the Yamaha manual at approximately 20° advanced. And while accelerating on the water it at first seemed to stay steady at 20°. But then when accelerating up into the high rev range (I could not see the Rev counter but probably 4000+ RPM?) the timing did start to advance beyond 20°! According to the driver we went to 5200 RPM (Yamaha askes for 4500+ RPM in the manual). I adjusted the timing back to 20° while at 5200 RPM then and there.

So Joe Reeves was right about the timing advancing at high RPM! (of course he was, a very experienced outboard mechanic!). But how many degrees offset were there in my case? I had to perform his method again, to measure that.

Finally, the results!
So I’ve put the Yam in the tub again, warmed her up to operating temperature (so as to avoid any Fast Start features playing with the timing. Don’t think the Yam has these features, but just to be sure) and performed the Joe Reeves Method. I disconnected the throttle from the ignition timing and set the timing a maximum spark advance. While doing that I noticed the RPM rising from 800 RPM to 1400 RPM. No problem, since the advancement shift only seemed to occur at high RPM.
I then used the timing gun to measure the spark advance, it was 18°. A two degree difference from the freshly set high RPM advance of 20°.

Conclusion
The Joe Reeves Method does work, no doubt about it. But with this outboard the high RPM spark advance delay to use with the Joe Reeves Method appears to be 2° in practice and not Joe’s 4°.
When using his method I would actually be boating around with 18° advance instead of 20°. Meaning less power, but also no risk of overheating because of too much advance.
I would therefore recommend the Joe Reeves Method as initial setting only, so test runs can be made safely until the timing can be set with a timing gun. Or as safest option if no other option for setting the timing is available.

And then there are the caveats …

1. This is only one test with one outboard done by one person.

I do believe other outboards will have the same principle of shifting spark advance at high RPM, but the amount could vary per make and type of outboard.

1. I did the testing alone.

And anyone can make mistakes such as:

• Stationary timing set wrong (double checked it)
• Looked at the wrong timing marker on the fly wheel (I marked the 20° mark in black, was hard to miss)
• Etc.

I don’t think I made these mistakes, but can I be really be sure of that?

So in all, it would be very useful if someone else were to test the Joe Reeves Method also. No need to pull the stunt I did by hanging over my outboard at high speed. One can just as easy take an outboard that has been timed correctly by a service station. Put it in a tub, disconnect the throttle link, turn the ignition to maximum advance and point the timing gun. Share the results. And Bob’s your uncle!

Hope you’ve found these posts useful and informative,
Hope to hear from you with comments or questions.
Cheers.