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1988 sr1 272 prop question

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Old 05-19-2017 | 10:20 AM
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The 260 horse 350 has a specified range of 4200-4600 but peaks at about 4400 on a dyno. What is the specified range for the 320efi, 5000-5400? I just meant that in real life on a dyno there probably isnt much gain from 5k to 5400 with that motor, maybe just a couple horse.
Be interesting to see what you find with the 21s
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Old 05-19-2017 | 11:01 AM
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Originally Posted by Mr Maine
The 260 horse 350 has a specified range of 4200-4600 but peaks at about 4400 on a dyno. What is the specified range for the 320efi, 5000-5400? I just meant that in real life on a dyno there probably isnt much gain from 5k to 5400 with that motor, maybe just a couple horse.
Be interesting to see what you find with the 21s
ok ill let you know maybe 2 weeks, boat is uncovered but still needs preseason, before going to the crooked. You on sebago?
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Old 05-19-2017 | 11:50 AM
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I run mostly the kennebec and midcoast but have been to sebago
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Old 05-19-2017 | 12:01 PM
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oh ok cool.
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Old 05-22-2017 | 09:44 PM
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I have an 87 272 with the same 320efi engines but I am also running the AlphaSS drives so it's not a direct comparison. I am currently running a pair of 23 mirage and have no trouble spinning the motors above 5000 rpm. I'm actually looking for a pair of the mirage pluses to bring the rims down a bit and hopefully improve my slip some.

Have you checked your tachs to verify they are accurate? I have seen them off by as much as a few hundred rpm in the past. The reason I ask is your slip seems very low (which is great if it's accurate) but I wouldn't be surprised if your tachs are a bit off and your actually closer or slightly above 5000 rpm.
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Old 05-23-2017 | 06:22 PM
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Originally Posted by JimNut
I have an 87 272 with the same 320efi engines but I am also running the AlphaSS drives so it's not a direct comparison. I am currently running a pair of 23 mirage and have no trouble spinning the motors above 5000 rpm. I'm actually looking for a pair of the mirage pluses to bring the rims down a bit and hopefully improve my slip some.

Have you checked your tachs to verify they are accurate? I have seen them off by as much as a few hundred rpm in the past. The reason I ask is your slip seems very low (which is great if it's accurate) but I wouldn't be surprised if your tachs are a bit off and your actually closer or slightly above 5000 rpm.
Oh. No
What would you recommend a method of checking the tachs?
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Old 05-23-2017 | 06:42 PM
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Compare to tach on timing light.
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Old 05-24-2017 | 07:37 AM
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Same method glenamy posted above. Get yourself a nice digital timing light with a tach output. Very useful tool.
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Old 06-05-2017 | 07:59 AM
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Originally Posted by JimNut
I have an 87 272 with the same 320efi engines but I am also running the AlphaSS drives so it's not a direct comparison. I am currently running a pair of 23 mirage and have no trouble spinning the motors above 5000 rpm. I'm actually looking for a pair of the mirage pluses to bring the rims down a bit and hopefully improve my slip some.

Have you checked your tachs to verify they are accurate? I have seen them off by as much as a few hundred rpm in the past. The reason I ask is your slip seems very low (which is great if it's accurate) but I wouldn't be surprised if your tachs are a bit off and your actually closer or slightly above 5000 rpm.
Howdy, I thought you had 21's if I recall.. when you bought that boat last year? also didnt you junk the EFI? and go with carbs?
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Old 06-05-2017 | 08:02 AM
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Originally Posted by JimNut
Same method glenamy posted above. Get yourself a nice digital timing light with a tach output. Very useful tool.
I have two tachs for each motor, I have the digital synchronizer and the VDO factory tachs they read the same... I just remembered
I will test with 21's soon a week from next sat. I did the full preseason yesterday finally.
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