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300 Tempest tune-up: Holley 650?

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Old 01-19-2007, 03:36 AM
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Default 300 Tempest tune-up: Holley 650?

Hello,
just a short question:
On a Mercruiser 300 Tempest I'am looking for a little better fuel economy, more chrispy throttle response, and some more allround performance.
I'am a newbie with this motor, but I know about engines in general.

Every info (tuning trick) is wellcome, if it is setup, fine tuning or components.
Thank you
nice rgds from Germany

andreas
[email protected]
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Old 01-19-2007, 08:26 AM
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Default Re: 300 Tempest tune-up: Holley 650?

I don't have the answer but maybe somebody else can help out. I had a temspest They where made by Mercuriser for one or two years (86-87). Its the 4 bolt 350 chevy engine coupled to the alpha drive. Can anybody help him out
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Old 01-19-2007, 12:35 PM
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Default Re: 300 Tempest tune-up: Holley 650?

I had a blown up 320 Efi, which was the same engine, other than the Efi (which is a whole nother story). They have all good internal parts. I changed to a carb, and put in a cam designed for lower rpm, and higher torque. I don't know what carb the Tempest came with, but if it's a Q jet, you won't find one that is more economical to run.
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Old 01-19-2007, 11:38 PM
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Default Re: 300 Tempest tune-up: Holley 650?

Is the Holley a vac or a double pumper?

If it is a double pumper it is more performance oriented and I can easily explain how to crisp it up if you tell me exactlly what it is doing. The 650 vac will be more fuel efficient and I can tell you how to crisp that one as well but that will usually cut into your economy a little.
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Old 01-21-2007, 12:00 PM
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Default Re: 300 Tempest tune-up: Holley 650?

Hello
Thanks for all your answers. A nice forum, all friendly people.

Its a small 4Winns Liberator (21") ,where this engine was stock displacement in 1986. (same as 4" thru-hull)

I must confess, I did pick up the boat at the Bremerhaven ro-ro terminal last tuesday.
Nevertheless I think it is a 4 bbl carb, possibly is a qudrajet carb on the engine. ( how can I post pictures here ?)
The first test-ride on Wed. showed the engine was performing fine , but a little rough, with a heavy bog, when coming up from idle.
I would not dare tinkiering a 2o year old carb, if a new one could solve it all.
That was my reason for asking.

If the quadrajet is a goodie and a Holley would not bring that much (with a higher consumption) I would leave my hands off.

Thanks for your infos,

a nice Sunday

rgds Andreas
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