2000 Johnson 50hp high speed timing issue

[stl808]

Hello, I picked up a 2000 Johnson 50hp, model #J50vlsig 3 years ago. During that time I have rebuilt/replaced the following; both carbs, OMS pump, both rollers on the throttle assembly, throttle cam lever, all electrical items under the cowling including the battery cable. (I reused the wiring harness. I did several random cont. tests and everything check out). I did the link & sync per the BRP service manual. Using the initial settings as per the manual, the motor fires up and idles great. The idle timing is 0 degrees. The RPM's are around 800 with the motor in gear and the boat free from the dock. (The boat is a 16' Mirrocraft, prop at 15 pitch) The motor accelerates fine, no stumbling or flat spots. My issue is the high speed timing. At 5000 RPM, the timing is 24 degrees, not the 19 plus or minus as spec'd. When I retard the high speed adjustment, it retards the low speed as well. (It would read briefly at -4 degrees or less until the motor died ). So I adjusted the low speed timing per the manual (using the bolt on the throttle cam lever) and redo the link & sync. I then checked the high speed timing again, lather, rinse and repeat the whole link & sync. Last year, I could get the high speed timing about 19 degrees, but the motor would hardly idle. (and the "adjustment" marks called out in the manual were way off) So I adjusted the motor to idle well and let the high speed be above spec. This summer, I decided to try the link & sync again, figure give myself a break. I had the same results. What am I missing? The flywheel key and magnets are fine. I used CDI for the new base timer and all other electronics. Thanks, Stephen

 

[Droid]

You are right at the time of OMC bankruptcy & BRP take-over. So your exact model # isn't listed in parts books.
I don't have any '01 manuals but the 2000 book shows the following (I'd guess the '01 manual would be basically the same if 1 was ever printed IDK. '02 & '03 manuals were somewhat combined).

Pics are out of order....

Preliminary adjustment doesn't call out a VL model but I assume you are using the 2 1/2" E model length.

Max spark advance 1st line NOTE says "correct test prop" this is not your 15P but a test wheel in a tank or at dock statically. Your not going to replicate this step exactly. I'm assuming you are running the boat with your 15P prop as you do this.

If it was me, I'd follow the adjustment to retard the timing towards 19 deg then go back to idle speed & throttle control rod as per ending NOTE. If you can't get all the way to 19 without a noticeable loss of high speed power, compromise a bit.

Remember, the initial 1/2" idle speed screw length is initial but not always the final setting. The cam follower roller should not be touching the cam. 1 deg ATDC is a target. You are using your prop in gear idling to achieve 800 RPM. Different weight boats with different pitch props may cause a variance. Also engine wear, temperature & air density will cause variance. 19 deg BTDC is more important. Too much advance can cause a pair of damaged pistons.

 

[stl808]

Hello and thanks for answering. The manual I have is for 2005 and yes I'm using the 2.5 length for the ignition linkage. When testing the high speed timing, it's on the water with someone driving the boat. Not ideal, but I can't find a test wheel. My concern was the over-advanced timing. It was a bit frustrating last night, but after looking at the throttle cam lever I can see now how the ignition roller works. As you increase the low speed screw, the roller moves up along the "flatter" section of the cam. This shortens the overall travel length of the ignition linkage, thus reducing the degrees between the low and high timing. The "starting" adjustments in the manual are what threw me last year. Everything worked great at the "starting" adjustments. Except for the high speed timing.

 

[racerone]

------Do not run it with timing advanced beyond 19 degrees !