BTDC timing setting while motor is running or cranking

berndie61

Cadet
Joined
Aug 12, 2008
Messages
8
Hello,


I read a lot of threads about adjusting motor. I have a 1990 90 hp Force. I read sometimes BTDC timing settings should be made while motor is running at high rpm or with WOT, sometimes cranking motor with starter and sometimes cranking motor with starter without spark plugs. When I say setting while motor is running, I mean just checking the marks not adjusting. I always check the timing while motor is running at WOT. I adjust the timing while engine is stopped.


Berndie
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: BTDC timing setting while motor is running or cranking

The method you are using is probably the most accurate way of checking timing at WOT. The reason it is not commonly done is that it is often difficult to do.

Speeding across the water at WOT with the cover off, holding the timing light close enough to the flywheel do get a reading can be dangerous depending on water conditions.

Checking the timing by turning the motor over with the starter is much easier and just about as accurate.
 

john from md

Commander
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Apr 13, 2008
Messages
2,184
Re: BTDC timing setting while motor is running or cranking

If you hit a wave and fall into the flywheel, you will be one ugly son of a gun IF you survive.

John
 

SwampThing

Petty Officer 2nd Class
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Nov 6, 2006
Messages
117
Re: BTDC timing setting while motor is running or cranking

Checking the timing by turning the motor over with the starter is much easier and just about as accurate.


Could you give a description of how to do this. The procedure outlined in the manual is somewhat confusing. I too have often thought that flying across the lake at WOT was a heck of way to have to set the timing.

TIA
 

john from md

Commander
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Apr 13, 2008
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2,184
Re: BTDC timing setting while motor is running or cranking

Real easy.
1. Jumper neutral safety switch with jumper wire or wrap wire around each terminal.
2. Put trottle in WOT.
3. Pull plugs, replace plug wire and ground plug shells by wrapping wire around them and then to ground. This is important so that your cdi modules don't get cooked. Plus you can observe spark as engine is turning.
4. Connect timing light. If using advance type of light, set pointer to 0.
5. Loosten lock nut on timing tower adjustment screw.
6. This can be done two ways. A. have someone turn the ignition switch to start while you shoot the flywheel with the timing light. B. Buy a remote starter switch from sears or harbor freight for $20 and do it yourself.

You are looking for a max of 30* BTDC cranking. This will give you approx
32* at WOT.


John
 

SwampThing

Petty Officer 2nd Class
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Nov 6, 2006
Messages
117
Re: BTDC timing setting while motor is running or cranking

Real easy.

3. Pull plugs, replace plug wire and ground plug shells by wrapping wire around them and then to ground. This is important so that your cdi modules don't get cooked. Plus you can observe spark as engine is turning.


John

Thanks for the quick response John.

Let me see if I get this right. In step 3 you're saying remove the plugs from the engine, reconnect the plug wires to the plugs, and then ground out the plug shells. I understand all of this, and the why of it. My problem with this is that isn't it a recipe for disaster should the fuel vapor now being expelled from the open plug holes ignite? Or am I missing something?

(EDIT) Okay simple solution now that I thought about it, disconnect the fuel supply. Force doesn't make it simple though because they don't use a quick disconnect for the supply hose. Thanks Again.
 

sho3boater

Petty Officer 2nd Class
Joined
Aug 4, 2009
Messages
168
Re: BTDC timing setting while motor is running or cranking

I never had a problem with fuel vapor since they don't draw the carbs well with no plugs in.

What you can do is back in the ramp just enough to get the prop under. Make sure the boat is strapped to the trailer bow and stern. Run the motor in the water to warm up and then run it in forward, adjust the trim and/or trailer depth so it can reach max rpm at near WOT and not over rev. Then check your timing that way. Watch the timing advance, with some good throttle you should be all the way advanced so you don't need WOT really. Or depending on what type of ignition you have you can see when it advances with the light. It makes a pretty spray of water. I would not recommend you do this unless you know what you are doing. Running the motor out of the water (the pickups) or over revving it will cause damage.

Or you can borrow a test wheel like boat shops use.
 

john from md

Commander
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Apr 13, 2008
Messages
2,184
Re: BTDC timing setting while motor is running or cranking

Don't worry about lighting off any mixture that comes out. It is blowing straight out and doesn't get rich enough to light off. I have done this a million times easily without any problems.

John
 
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