Question On Setting Timing 1993 90HP Sportjet

[cowansauto]

Somehow the nut and screw on the trigger arm accidentally came loose on my boat recently while breaking in my rebuild. Unfortunately the trigger arm got moved around some so I'm unsure if the timing is correct. The boat was running around 3000 RPMs at idle when I had it at the dock and I wasn't able to correct this on the spot so we pulled back out of the water.

I've looked on this forum, in my service manual, etc and I've learned about the two critical timing marks. Here's my problem though, I do not have the fancy tester that's shown in the factory manual to place the plug wires on and I'm afraid to start running it out of time for fear of burning a hole through the piston! I found the info on using a distributor cap as a multi plug tester but was a little confused about some of the materials they used.

If the timing is way off and I do get it running without taking the plugs and wired out, at WOT to check the timing specs, how long would it take to cause damage? How sufficient is it getting the timing specs by not taking plugs and wires off?

http://motorka.org/doc/mercury/service_manual/jet/SJ90_120_95xr_125xr_831996r1/sec2d.pdf

Thanks for your help!

 

[jerryjerry05]

Re: Question On Setting Timing 1993 90HP Sportjet

http://forums.iboats.com/force-chry...etting-timing-your-force-outboard-607788.html
Kiker14 JUST posted a video on that very subject. Look for it. Remove the plugs.

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

http://forums.iboats.com/force-chry...etting-timing-your-force-outboard-607788.html
Kiker14 JUST posted a video on that very subject. Look for it. Remove the plugs.

I saw this video last night and wondered about it. I don't believe my engine has the switch that's mentioned at the beginning of the video though. Also, is it okay to use the ground where the negative battery cable attaches to the engine as the ground for the wires attached to the spark plug wires?

 

[foodfisher]

Re: Question On Setting Timing 1993 90HP Sportjet

Yes. A closer engine bolt might be more convenient though

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

I used the method above today. It looks like I will have to override the "safety switch" in order to actually start the engine in gear at WOT. The throttle control lever will only go so far in forward gear with the safety engaged. It wont start without the switch engaged. It will allow me to give it a little throttle in forward gear, but no where near up to WOT. The manual doesn't even cover the fact that you have to do other steps to put the engine into WOT without running the engine.

When I was looking through the manual posted above, it mentions BTDC timing of 8-10* at 950-1100 RPM's. But then it also mentions cranking speed timing of 32*. This confuses me. Could someone explain the difference?

 

[jerryjerry05]

Re: Question On Setting Timing 1993 90HP Sportjet


Use a jumper or jump box to get past the neutral safety switch.
The throttle needs to go all the way forward.
Cranking speed is, plugs out, throttle open all the way(might need someone to hold it) key switch on.
Then as the motor turns that's cranking speed.
Hold the timing light as the motor turns.

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

Please help me clarify something: The link above mentions "CHECK WOT IGNITION TIMING W/ENG NOT RUNNING" and mentions to get timing to 32* BTDC. What this is saying is that with the engine JUST CRANKING/HAVING PLUGS OUT/WOT, etc your timing is actually going to be higher than it actually will be if ENGINE RUNNING/PLUGS IN/AT WOT, etc.

AND

The method outlined in the manual link posted above: "CHECK WOT IGNITION TIMING W/ENG NOT RUNNING" and the method "CHECKING TIMING AT CRANKING SPEED" are actually both telling you to set timing to the same (32*) because your looking for the same timing point on both when the engines not running.

Now that I think about it, after I got the engine rebuilt I had trouble getting spark (fixed now) and had to jump the neutral safety switch to test if it was the culprit. On these models it is just a small cherry switch. When the shift control arm is in gear, there is no continuity on the switch. One wire comes from the ignition swith into the neutral switch and the other eventually goes out to the a stud on the starter solenoid. This should be bypassed by simply just removing the two wires and connecting them.


I'll go back tomorrow and get the timing down!

 

[jerryjerry05]

Re: Question On Setting Timing 1993 90HP Sportjet

I have a piece of wire with an aligator clip on both ends. Makes a great bypass.

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

Well today was the first day we actually got out and about on the boat. It did pretty good. It planed out almost near WOT. Unfortunately the WOT RPMs are too high.Wide open throttle was 6800 rpms! That needs to be around 5000 RPMs MAX I believe.

I recorded Idle showing 1100 rpms at 10* BTDC which is close to factory specs.

 

[jerryjerry05]

Re: Question On Setting Timing 1993 90HP Sportjet

The over rev?? There is a PWC section. They would probably be able to answer that question.
If you were operating with a regular prop?

 

[Brad_Ct]

Re: Question On Setting Timing 1993 90HP Sportjet

The rev limiters on these engines are set for 5800 RPM. As far as setting the timing, I pulled the plugs and grounded them instead of buying the recommended tool, set the throttle to WOT in gear turned the ignition switch on and used a remote starter switch between the battery and starter solenoid. Then with a timing light set the timing to 32* BTDC.

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

How did you get the engine to start in gear or at WOT throttle? Did you jump the neutral safety switch?

My engine was running 6800 RPMs at one point according to my timing/tach light tool. I'd say the rev limiter is bad then?

 

[Brad_Ct]

Re: Question On Setting Timing 1993 90HP Sportjet

You don't need to start it to set the timing.

 

[cowansauto]

Re: Question On Setting Timing 1993 90HP Sportjet

You don't need to start it to set the timing.

Thanks for the reply, but we've already discussed that. In my last post I asked you about what method you used to overide the neutral safety switch. Do you have a Force outboard or a SportJet?