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Any Info On 300 Promax

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Old 08-08-2006, 05:43 PM
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Default Any Info On 300 Promax

Looking For Info On 300 Promax Motor's
How Do They Run ?
How Many Hour's Before Rebuild?
What The Compression Should Be ?
Any Other Info Would Be Great That You Mite Have

Thank's
Mike
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Old 08-08-2006, 07:36 PM
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Default Re: Any Info On 300 Promax

I have a pair of 300 promaxes. They have been great motors so far. I have been told that compression should be around 130
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Old 08-08-2006, 07:38 PM
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Default Re: Any Info On 300 Promax

Thank's

any more info out there ?
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Old 08-08-2006, 07:42 PM
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Default Re: Any Info On 300 Promax

They are great motors and you can run the chit out of them!! I think the only reason they stopped building them is emissions??
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Old 08-08-2006, 09:12 PM
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Default Re: Any Info On 300 Promax

any idea how many hour's they should run before rebuild ?

thank's
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Old 08-09-2006, 05:42 AM
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Default Re: Any Info On 300 Promax

Hours depends on how you run them, mine got 150 very hard (race hours) before i nipped a piston and that was only becasue the headgasket let go, o-ring the heads or put simonmotosports heads on them, compression is usually in the 120ish range, they are an understressed motor, if your just cruising no reason you shouldn't see 500-600 hours out of them. the early 98's only had a 6100rpm limit which can be a pain, pretty hungry on fuel about 25-28gph per motor at full noise.
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Old 08-09-2006, 07:54 AM
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Default Re: Any Info On 300 Promax

I have a pair on a 28 Skater, the powerheads have been trouble free since I have owned the boat. I have about 340 hours on each motor. I normally run my motors around 4600-4700 range cruising. They are hungry on fuel and oil once you get to 5k and above.
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Old 08-09-2006, 12:39 PM
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Default Re: Any Info On 300 Promax

I have a pair on my 30 shadowcat.They are 99's.I run them mostly between 4000 to 4500.At 4000 I am cruising right around 70mph.They are trouble free.Gas Oil GO!i am in the process of dialing in the boat.I am sure there is more speed in it.I have the engines mounted on the transom with no setback and no jackplate turning 28 Labbed Bravo 4 blades.Hey guys what type of water pressures and temps are you running.The only problem I am having and this is not the motor is when I am trimming up I start to loose water pressure and the temp goes up.I am thinking that this is because the engines are so close to the transom that it is not getting good water because the transom is kind of disturbing the water I am thinking some setback may get the lowers in cleaner water.What do you think?
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Old 08-09-2006, 12:49 PM
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Default Re: Any Info On 300 Promax

i hace 2003 300x's on a 30 spectre on jack plates...i see anywhere from 5psi at idle to mid teens to low 20's depending how shes trimmed. as far as temps 1teens to low 120's. motos have 180+ hrs on them and other then 1 thrown alternator belt, i lower unit and 1 prop shaft...no probs.
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Old 08-09-2006, 01:54 PM
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Default Re: Any Info On 300 Promax

sportmaster lowers are the weak link
 
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