25ft Carrera prop size

[25ftcarrera]

I recently purchased a 1984 Carrera 25ft off shore cruiser, built in Southern Calif. w/ 350 chevy A290 with volvo-penta 280 IO. The prop has been changed and I was wondering if anyone knew the factory prop size. This boat is the same hull as the eliminator of that era.

 

[alldodge]

I recently purchased a 1984 Carrera 25ft off shore cruiser, built in Southern Calif. w/ 350 chevy A290 with volvo-penta 280 IO. The prop has been changed and I was wondering if anyone knew the factory prop size. This boat is the same hull as the eliminator of that era.

That's always a tuff question. I would guess it's between a 17 and 21 pitch and depends on drive ratio and weight. What rpm and speed are you getting now at WOT?

:welcome: to iboats

 

[25ftcarrera]

Haven't had this boat in the water yet. The guy that owned it said it topped out at 4800rpm Its a 15-1/4 x17 ss prop. My 79 - same boat and motor had the factory prop and it topped out at 5200 rpm. One boat repair place said this SS prop was too big for the boat. Volvo has about 15 options for this OD LOL. I'm thinking it should be a 14x21 or in that neighborhood. Drive ratio is 1:62 - 1 boat probably weighs about 4k at least. IIRC I was told the 79 with trailer was just over 6K.

 

[alldodge]

Haven't had this boat in the water yet. The guy that owned it said it topped out at 4800rpm Its a 15-1/4 x17 ss prop. My 79 - same boat and motor had the factory prop and it topped out at 5200 rpm. One boat repair place said this SS prop was too big for the boat. Volvo has about 15 options for this OD LOL. I'm thinking it should be a 14x21 or in that neighborhood. Drive ratio is 1:62 - 1 boat probably weighs about 4k at least. IIRC I was told the 79 with trailer was just over 6K.

WOT at 4800 for your setup figuring 10% slip you should reach 42.4 mph. I think you have the right prop. The 4800 rpm WOT for a 1984 engine is correct, putting a 21 on it will cause you to burn more fuel and slow you top end. To turn 5200 with your 1979 could be done but someone did some engine work and had it balanced or the tach was off

 

[25ftcarrera]

WOT at 4800 for your setup figuring 10% slip you should reach 42.4 mph. I think you have the right prop. The 4800 rpm WOT for a 1984 engine is correct, putting a 21 on it will cause you to burn more fuel and slow you top end. To turn 5200 with your 1979 could be done but someone did some engine work and had it balanced or the tach was off

No, the 79 was brand new and stock and my friend at the time that had the same boat only a 1978 his rpm at WOT was the same. I know this SS prop is oversized and not stock. I kind of remember the dealer saying the boat was set up for a 5200 rpm max. I wish I had written down the prop size but when I sold the 79 never thought I would need it.

 

[alldodge]

Guess you have some engine problems then. My reasoning is, you currently have a smaller prop and can only turn 4800, if you install a 21 pitch your rpms will only be reduced. If you had the power to turn a 21 even at 4800 then with the 17 pitch you would over rev the engine. If you do over rev then putting a 21 on may be the way, but so far the PO is saying that all they have been able to get out of it is 4800.

The rpms at WOT is coming from the Merc service manuals

 

[Bondo]

No, the 79 was brand new and stock and my friend at the time that had the same boat only a 1978 his rpm at WOT was the same. I know this SS prop is oversized and not stock. I kind of remember the dealer saying the boat was set up for a 5200 rpm max. I wish I had written down the prop size but when I sold the 79 never thought I would need it.

Ayuh,.... The 5.7l, 350s were all pretty much 4800 rpms at Wot, especially in the vintages We're talkin' 'bout,....

If you, 'n yer Bud were runnin' 5200 rpms, that's Over revin', plain, 'n simple,...

'n AllDodge is right, that if ya can turn the 17" pitch prop to 4800 rpms, goin' to a 21" will lower the rpms at Wot, not raise 'em,....