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Old 08-15-2018, 07:56 AM
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88falcon 88falcon is offline
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Boat: 1988 centurion falcon
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How do you tune ?

Good morning TT,

Just curious on how you all tune your motors (specifically 351). I'm not having any issues, the boat is running excellent thanks to all the advice I have received but I was just curious on how others may tune / dial in their engines and carb.

The process I used was:

On the trailer

1st) set timing at 10 using timing light.

2nd) checked dwell and set it at 31 using a dwell meter .( this is before I did a EI conversion and had points )

3rd) checked timing again (when adjusting the dwell it can change timing very slightly )

4th) set idle speed as close to 600 as I could using a dwell meter with a built in rpm scale for low and hi speed rpms. (when i had points it didnt like to idle this low it was about 650-700 , now with EI 600 is fine)


On the water

5) when on the water I had to slightly adjust the fuel air mixture on the carb to be richer ( originally set at 1.5 turns out , now it's probably 1.75 turns out ) boat now starts decent when cold and very easy when warm.

6) I always put her through a wide variety of speed / rpm tests and make minor adjustments if nessecary.

Again I'm not having any issues, I'm just curious on others processes to ensure I'm going through the correct motions and not missing a step and also because I get asked from friends and family for help on their boats from time to time and I want to be giving good honest advice.

Thanks fellas !






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Old 08-15-2018, 10:44 AM
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paco_06 paco_06 is offline
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Sounds like you've got it whipped. Only thing I can add, and I may be wrong because I usually set everything by ear/feel, is timing should be set on a warm engine which is hard to do on the trailer.
Idle is 600-800 rpm while in gear. And lastly, to set air screws, just turn clockwise one at a time till the engine starts to stumble, then back off a half round. This will need to be done before final idle speed is set.

But again, really sounds like you have it down! Oh, and try not to learn too much or you'll be the neighborhood mechanic

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Old 08-15-2018, 12:14 PM
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Remember, you can tune a piano but you can't tuna fish.
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Old 08-16-2018, 06:44 AM
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88falcon 88falcon is offline
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Quote:
Originally Posted by paco_06 View Post
Sounds like you've got it whipped. Only thing I can add, and I may be wrong because I usually set everything by ear/feel, is timing should be set on a warm engine which is hard to do on the trailer.
Idle is 600-800 rpm while in gear. And lastly, to set air screws, just turn clockwise one at a time till the engine starts to stumble, then back off a half round. This will need to be done before final idle speed is set.

But again, really sounds like you have it down! Oh, and try not to learn too much or you'll be the neighborhood mechanic

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How easy should it be to cold start ? When I first rebuilt the carb I had the mixture to rich and the boat would cold start instantly, and idle great however after a wot run it would die after i would let it idle for a few minutes. (flood it self essentially) . That was prior to knowing how to adjust the carb properly . Now after leaning it out slightly my starts are a little more difficult not bad , but I cant just pump the throttle and than start it , i have to hold it open slightly and start it at about 1k rpms. Once I start it I can drop it down to idle immediately and it's fine. I wonder if your ear / feel test on the carb could get it dialed slightly better.

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Old 08-16-2018, 06:59 AM
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paco_06 paco_06 is offline
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Quote:
Originally Posted by 88falcon View Post
How easy should it be to cold start ? When I first rebuilt the carb I had the mixture to rich and the boat would cold start instantly, and idle great however after a wot run it would die after i would let it idle for a few minutes. (flood it self essentially) . That was prior to knowing how to adjust the carb properly . Now after leaning it out slightly my starts are a little more difficult not bad , but I cant just pump the throttle and than start it , i have to hold it open slightly and start it at about 1k rpms. Once I start it I can drop it down to idle immediately and it's fine. I wonder if your ear / feel test on the carb could get it dialed slightly better.

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Should start easy. I wrap the throttle wide open 3 times to pump a little fuel in and instantly fires. Do you have the choke set right? Loosen the three screws for the choke and turn till it barely closes and tighten. This needs to be done on a cold engine. And I couldn't tell you how many turns on the air screws, just clockwise till it stumbles then back off a half round. All in all though, really sounds like you've got it about right. Really doesn't matter how well it runs when cold, just as long as it's satisfactory when warm!

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Old 08-16-2018, 07:01 AM
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88falcon 88falcon is offline
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Boat: 1988 centurion falcon
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Quote:
Originally Posted by paco_06 View Post
Should start easy. I wrap the throttle wide open 3 times to pump a little fuel in and instantly fires. Do you have the choke set right? Loosen the three screws for the choke and turn till it barely closes and tighten. This needs to be done on a cold engine. And I couldn't tell you how many turns on the air screws, just clockwise till it stumbles then back off a half round. All in all though, really sounds like you've got it about right. Really doesn't matter how well it runs when cold, just as long as it's satisfactory when warm!

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Cheers to that !

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