Need to know what size prop

[treeeman00]

I have a 1987 2450 Bayliner trophy. I bought the boat with no outdrive. Originally it was an OMC outdrive and a OMC 305. I am putting a 350 chevy in it and I bought a OMC Cobra outdrive for it. Since the outdrive is not the original im not sure if the prop is the right size. Anybody have the same boat or know what your talking about on props what would be the recommended prop size for my boat. Everything is all stock also. Thanks for your help!

 

[Bondo]

Re: Need to know what size prop

Since the outdrive is not the original im not sure if the prop is the right size.

Ayuh,... Welcome Aboard,... So long as the drive ya bought is the Right gear ratio,...

Whatever prop that's on it will suffice to run it, 'n get some usefull numbers to see what ya need....

Read the "Read This First" at the top of this forum to see what's needed to pick the Right prop...

 

[steelespike]

Re: Need to know what size prop

Do you know the gear ratio, may be stamped on it.
You could rotate the input shaft count the revolutions for one turn of the prop shaft.Probably have to make index marks
to make an accurate count.

 

[treeeman00]

Re: Need to know what size prop

all that i know if that the guy I bought it off of said that it came off of a boat with a 350 chevy. So I could pull the top cover and count the teeth?

 

[steelespike]

Re: Need to know what size prop

I'm not sure but I believe the ratio is a combination of the top and bottom gears.
If the drive isn't installed just count the input shaft revolutions for one prop revolution.
Otherwise the only way I know to be sure of the ratio is to pull the plugs and rotate the engine.

 

[treeeman00]

Re: Need to know what size prop

do you mean count the splines on the driveshaft?

 

[steelespike]

Re: Need to know what size prop

do you mean count the splines on the driveshaft?

No,with the drive in gear rotate the input shaft count the revolutions to make the prop turn once.
You'll need to make a mark to be accurate. Assuming intended for the 350 the count will likely be less that 2 revolutions.

 

[sschefer]

Re: Need to know what size prop

No,with the drive in gear rotate the input shaft count the revolutions to make the prop turn once.
You'll need to make a mark to be accurate. Assuming intended for the 350 the count will likely be less that 2 revolutions.

Wouldn't it be easier to mark the prop then turn the input shaft one full revolution and count the prop revolutions. Maybe that's what you meant and I'm misreading it.

 

[steelespike]

Re: Need to know what size prop

Prop will turn less than input. If the drive is intended for a 5.0 input would likely be something like 1.6 turns to maybe as high as 1.8.
Could be a little less.I'm sure no volvo expert but it appears to me that Volvo might have a number of significantly different ratios for a 5.0 depending on the application than say Mercruiser would.

 

[treeeman00]

Re: Need to know what size prop

this may be a dumb question but is the input shaft the driveshaft?

 

[steelespike]

Re: Need to know what size prop

With the drive removed from the boat the shaft that connects to the motor adapter( again not acquainted with Volvo)
is the input shaft (my term).

 

[steelespike]

Re: Need to know what size prop

Prop will turn less than input. If the drive is intended for a 5.0 input would likely be something like 1.6 turns to maybe as high as 1.8.
Could be a little less.I'm sure no volvo expert but it appears to me that Volvo might have a number of significantly different ratios for a 5.0 depending on the application than say Mercruiser would.

Disregarde my reference to Volvo But the ratio still applies Just may vary from my suggestions.

 

[steelespike]

Re: Need to know what size prop

Prop will turn less than input. If the drive is intended for a 5.0 input would likely be something like 1.6 turns to maybe as high as 1.8.
Could be a little less.I'm sure no volvo expert but it appears to me that Volvo might have a number of significantly different ratios for a 5.0 depending on the application than say Mercruiser would.

Disregard my reference to 5.0 and Volvo I had a BF. A 350 OMC could have a ratio of 1.40.
Would depend on the year and hp. If it is stamped on the outdrive it would save having to go through the procedure.