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Old 08-29-2005, 02:09 PM
marknanh marknanh is offline
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Distributor Timing: 14-deg BTDC?

I recently installed a Prestolite electronic ignition module (from SkiDim) in my 1988 Mastercraft TriStar. Last night I re-timed the Indmar 351 engine and found that the boat would cut out at idle if set at less than ~14-deg BTDC. The manual states that 10-deg BTDC is correct.

I haven't timed the engine since moving from NY (700 ft MSL) to NV (4700 ft MSL). Would the change in either the distributor or the altitude cause the increase in position? Is there any cause for concern such an advanced 14-deg setting?

Regards,
Mark
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Old 08-29-2005, 02:32 PM
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PeteS PeteS is offline
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Quote:
Originally Posted by marknanh
I recently installed a Prestolite electronic ignition module (from SkiDim) in my 1988 Mastercraft TriStar. Last night I re-timed the Indmar 351 engine and found that the boat would cut out at idle if set at less than ~14-deg BTDC. The manual states that 10-deg BTDC is correct.

I haven't timed the engine since moving from NY (700 ft MSL) to NV (4700 ft MSL). Would the change in either the distributor or the altitude cause the increase in position? Is there any cause for concern such an advanced 14-deg setting?

Regards,
Mark
You shouldn't be running at 14 degrees BTDC, Mark. Couple of questions: did you bypass the ballast resistor as stated in the manual when installing the ignition? What is your idle speed set at? What was your idle speed set at for testing? Have your tried running it with the distributor fully fastened down after adjustment? Let me know those items, and maybe I can help -- went through similiar issues with my '88.
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Old 08-29-2005, 03:40 PM
marknanh marknanh is offline
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I did bypass the ballast resistor but did not run the engine after tightening the distributor base clamp. Thanks for the suggestion.

I should also tell you that (a) my tachometer is busted so the 600 rpm timing bogey was an estimate and (b) since moving to NV I have not resized the jets in my carbeurator. My friends suggest that I decrease the size of the primary and secondary jets to lean out the engine.

Your thoughts?
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Old 08-29-2005, 03:54 PM
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PeteS PeteS is offline
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When mine behaved the way you are describing yours, it was a few things. First, the distributor was not grounded well when I was testing the timing at 600 RPM, so it was stalling when the base clamp was loose.

Secondly, your air/idle adjustment screws on your carb could be off as well. Check those out, and report how many turns from seated they are. You could be running to lean or rich, and at the low RPM's and the correct timing you may be stalling. Mine are both at 2 turns from seated, as a point of reference.

And lastly, make sure you check your timing and your air/idle with the boat fully warmed up. It will stall at that low of RPM's if the motor is cold. I'd suggest making small adjustments to the distributor, and re-tightening the base clamp before hitting it with a timing light.

I would do this: let the boat warm up fully. Then lower the idle as much as you can using the primary idle set screw without the boat stalling. Then, adjust your air/idle mixture screws. Now lower the idle some more. My guess would be that you would now be at 600 RPM or so. Next, test and adjust the timing, tightening the base clamp back up after each adjustment with 10 degree BTDC as your goal.

Once complete, you'll have to bring your idle up 100 RPM or so, and re-adjust the air/idle circuits while doing so. If all of those action items fail, then it could be your jets. But I wouldn't get into that quite yet. Let me know what you find out.
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Old 08-29-2005, 05:07 PM
jimmer2880 jimmer2880 is offline
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14 deg BTDC is fine. I used to have my 351 somewhere around 18 deg. As long as it's not pinging - you're fine (I've been told).On the new fuel-injected boats, 10 deg is where it needs to be though & you don't gain anything if you're anything other than that (since the computer takes care of all advance once above idle).
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