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Prop question??

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Old 06-09-2011, 01:53 AM
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Default Prop question??

Hello!! I am a newbie to the site! I have a question of which prop i should change to. I was runnin a 23 foot powerquest with a 23 pitch stainless Mirage, the boat was powered by a 454. I upgraded over the winter to a 502 EFI, and i can barely get 4200 RPM out the boat now. What do I do to get more r's out it? Thank you!!!
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Old 06-09-2011, 07:23 AM
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How much hp was in the old 454 and what rpm did you spin at?
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Old 06-09-2011, 11:33 AM
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Are you running the same 23" prop????
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Old 06-09-2011, 11:55 AM
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yes its the same prop as before the 454 was 325 hp the 502 is 425hp, thanks
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Old 06-09-2011, 11:58 AM
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oh, and it was gettin 4750RPM before

Last edited by pqbenny; 06-09-2011 at 12:11 PM.
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Old 06-09-2011, 12:37 PM
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Pull the 502EFI out and rebuild it?

First off, you should be spinning a 25p prop with that set up, or 24 4 blade. The fact that you can't even spin the same prop as the 330hp shows that somethign is wrong. The weight of the engines is so close that it is a non issue. I would tach the engine directly with something reliable to verify.

Was the 502EFI new or fresh?

If it was used did you perform compression and leak down tests before the install?
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Old 06-09-2011, 12:42 PM
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Quote:
Originally Posted by 4bus View Post
Pull the 502EFI out and rebuild it?

First off, you should be spinning a 25p prop with that set up, or 24 4 blade. The fact that you can't even spin the same prop as the 330hp shows that somethign is wrong. The weight of the engines is so close that it is a non issue. I would tach the engine directly with something reliable to verify.

Was the 502EFI new or fresh?

If it was used did you perform compression and leak down tests before the install?
Agreed,

BUT before I rebuilt the engine I would check a few things

Fuel Pressure, was the 454 EFi? I thought the EFI 454's were 310HP, and 385?
Electrical, check all wiring to make sure you are getting full spark, advance etc.

It only takes fuel and fire to make power, if the engine is healthy, it is one of thise 2 things, otherwise the engine may not be tired.
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Old 06-09-2011, 01:12 PM
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I am sure everyone is assuming that the drive (gear ratio) was not changed.
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Old 06-09-2011, 02:55 PM
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compression is good heads were just redone and the drive was replaced as well with the swap. The drive was bought w the 502, was a complete setup w 50 hrs from my buddy.
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Old 06-09-2011, 03:05 PM
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ok i just went a ran the boat in the driveway. I noticed gas was dribbleing out of the over flow hose down into the mechanical fuel pump. so I pulled the cover off of the fuel cooler, and under the cover there was the rubber diaphram piece that had a whole in it, so it was allowing fuel to dump out. where there overflow hose comes out. Do ya think that may have been the prob?
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