I have purchased a used 1975 Formula Thunderbird. It has a 6 cylinder
mercruiser with an alpha i/o.

the prop is a little beat up.

what is the common prop size used on a boat like this.

19 footer with the six cylinder.

there are so many to choose when i look into a catologe or on ebay.

thanks

sonofadocker

"sonofadocker" wrote in message
oups.com...
I have purchased a used 1975 Formula Thunderbird. It has a 6 cylinder
mercruiser with an alpha i/o.

the prop is a little beat up.

what is the common prop size used on a boat like this.

19 footer with the six cylinder.

there are so many to choose when i look into a catologe or on ebay.

thanks

sonofadocker


The diameter and pitch of your existing prop will be stamped on the outside
of the hub. If you are happy with how the boat performs, stick with the
same numbers.

You can also take your prop (assuming it is aluminum) and have it repaired
for about half the cost of buying a new one.

If you are replacing with the exact same prop, get the model number as
well (On the back side of the hub). Pitch and diameter are important
but so is blade area. Getting the model number will assure you have the
same prop. I went from Alum to SS on my tender and I went through 3
props until I got one just right. The new alum vortex props tend to
have less surface area then their Merc counterparts and also less than
their michigan SS counterparts. If the prop is all there (no missing
aluminum) then a rebuild would be cheaper. If it has large gouges
then I suggest replacement (Small chips can be banged out but larger
ones are not worth the trouble and tend to make the prop weaker)



JimH wrote:

"sonofadocker" wrote in message
oups.com...

I have purchased a used 1975 Formula Thunderbird. It has a 6 cylinder
mercruiser with an alpha i/o.

the prop is a little beat up.

what is the common prop size used on a boat like this.

19 footer with the six cylinder.

there are so many to choose when i look into a catologe or on ebay.

thanks

sonofadocker



The diameter and pitch of your existing prop will be stamped on the outside
of the hub. If you are happy with how the boat performs, stick with the
same numbers.

You can also take your prop (assuming it is aluminum) and have it repaired
for about half the cost of buying a new one.

Thanks for the last two replies.
The boat is docked now and i can not see the stamping on the prop when
i went into the water to look.
i thought someone might know what a common prop is for the engine size
and lenght of the boat.
we just go around the bay at low or half throttle. i have never had the
boat to full throttle yet or made the boat work hard. i would not know
the difference between props performance at this time.

thanks

sonofadocker.

Ed wrote:
If you are replacing with the exact same prop, get the model number as
well (On the back side of the hub). Pitch and diameter are important
but so is blade area. Getting the model number will assure you have the
same prop. I went from Alum to SS on my tender and I went through 3
props until I got one just right. The new alum vortex props tend to
have less surface area then their Merc counterparts and also less than
their michigan SS counterparts. If the prop is all there (no missing
aluminum) then a rebuild would be cheaper. If it has large gouges
then I suggest replacement (Small chips can be banged out but larger
ones are not worth the trouble and tend to make the prop weaker)



JimH wrote:

"sonofadocker" wrote in message
oups.com...

I have purchased a used 1975 Formula Thunderbird. It has a 6 cylinder
mercruiser with an alpha i/o.

the prop is a little beat up.

what is the common prop size used on a boat like this.

19 footer with the six cylinder.

there are so many to choose when i look into a catologe or on ebay.

thanks

sonofadocker



The diameter and pitch of your existing prop will be stamped on the outside
of the hub. If you are happy with how the boat performs, stick with the
same numbers.

You can also take your prop (assuming it is aluminum) and have it repaired
for about half the cost of buying a new one.

http://sites.mercurymarine.com/porta...che ma=PORTAL

If that doesn't work, just go to Mercurymarine.com and go to prop
selector.

You will need the length of the boat, HP of engine, approx weight if you
have it.

The tool will give you some suggestions.

ALSO, you can call formula.

There is another tool at michiganwheel.com


sonofadocker wrote:
Thanks for the last two replies.
The boat is docked now and i can not see the stamping on the prop when
i went into the water to look.
i thought someone might know what a common prop is for the engine size
and lenght of the boat.
we just go around the bay at low or half throttle. i have never had the
boat to full throttle yet or made the boat work hard. i would not know
the difference between props performance at this time.

thanks

sonofadocker.

Ed wrote:

If you are replacing with the exact same prop, get the model number as
well (On the back side of the hub). Pitch and diameter are important
but so is blade area. Getting the model number will assure you have the
same prop. I went from Alum to SS on my tender and I went through 3
props until I got one just right. The new alum vortex props tend to
have less surface area then their Merc counterparts and also less than
their michigan SS counterparts. If the prop is all there (no missing
aluminum) then a rebuild would be cheaper. If it has large gouges
then I suggest replacement (Small chips can be banged out but larger
ones are not worth the trouble and tend to make the prop weaker)



JimH wrote:


"sonofadocker" wrote in message
egroups.com...


I have purchased a used 1975 Formula Thunderbird. It has a 6 cylinder
mercruiser with an alpha i/o.

the prop is a little beat up.

what is the common prop size used on a boat like this.

19 footer with the six cylinder.

there are so many to choose when i look into a catologe or on ebay.

thanks

sonofadocker



The diameter and pitch of your existing prop will be stamped on the outside
of the hub. If you are happy with how the boat performs, stick with the
same numbers.

You can also take your prop (assuming it is aluminum) and have it repaired
for about half the cost of buying a new one.