King Cobra swap to Sx Dps , what ratio and propellers set ?

[bolbic33]

hi all,

i'm from france, so i apologize by advance for my english level ....
I have a chris craft crowne 282 , powered by an OMC 454 (carb , 330 HP) with a king cobra on (ratio 1.43).

I realize that OMC parts are NLA, so i want to put a volvo sx DPS on it.

I found a dps sterdrive, in a good shape.
The ratio is 1.51 , and the propellers set is F4 ( F : 38511461 / R : 3851474 )


The dps saler told me his engine (a 5.0L OMC) reached more than 5000 rpm with that drive ...

If a 5.0L reach more than 5000 rpm, does my 454 will not get higher rpm ?


The dps saler can sale me the drive with F7 propeller set if needed.

Does this ratio and prop size match for my 454 ?

What is the ideal ratio and prop size for my configuration ?



PS : i read english better than i write it :s


Thanks by advance !
Bolbic

 

[Don S]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

OMC 454 (carb , 330 HP) with a king cobra on (ratio 1.43)

That sounds like the OMC version Cone Clutch King Cobra, is it? If so, the conversion can not be done on that setup.

I found a dps sterdrive, in a good shape. The ratio is 1.51 ,

Have never heard of a 1.51 ratio on a DP. 1.78 is the normal ratio for a carbed 454.

 

[bolbic33]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

HI Don,

Thanks for your quick response!

Yes, it's the cone cluth.

I (think) got everything needed ( see on attached pic), but the bellhousing ( maybe i will need the coupler ? )

if i remove everything but the 454 , i cannot put this DPS on it ?

Thanks a lot !

Best regards,

Bolbic ( Bordeaux , France )

 

[bolbic33]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

i forgot to tell you, the upper unit is brand new, and indicate 1.5 (or 1.51 ?) ratio.

 

[Don S]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

Yes, it's the cone cluth.

I (think) got everything needed ( see on attached pic), but the bellhousing ( maybe i will need the coupler ? )

if i remove everything but the 454 , i cannot put this DPS on it ?

That will work, I assumed:facepalm: you were trying to convert it by using the kit from Volvo used on the regular Cobra transom shield, not replacing the complete transom shield.

If you don't know the gear ratio of the lower unit, then it's hard to tell what it is.

What you need to do is put the drive in gear, turn the ujoint shaft until the prop shafts start moving, then mark them and continue turning the ujoint shaft to make one complete revolution of the prop shaft. Count how many turns of the ujoint shaft it will take to make one revolution of the prop shafts.
You will get either 1-3/4 (approximately) turns, almost 2 turns, or 2 and just over a quarter turns.

You want 1-3/4 turns.

 

[bolbic33]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

Thanks Don

yes, i want to change everything.

Do i need to change the bellhousing too ? Or the Omc one will match ?
what about the coupler ?

I will check for the ratio like you told me , and come back to you

in France, i found no one to give me this information ... I'm glad iboats forum exists !

Thanks again

Bolbic

 

[Don S]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

Do i need to change the bellhousing too ? Or the Omc one will match ?
what about the coupler ?

Have no idea, never changed one.

 

[Don S]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

I finally found this bulletin that might help you determine the gear ratios.

 

[bolbic33]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

Thanks for the doc Don !

i just made the check with the drive owner.

For 1 ujoint shaft revolution, the propeller made a little (very little) more than 0.5 revolution.

It seems to match with the indicate ratio of 1.51 / 1 tapped on the brand new upper unit.

Does this drive will fit my 454 ?
Does the F7 propellers set is better than the F4 set the drive comes with ?

Thanks by advance,

best regards,

Bolbic

 

[Don S]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

It seems to match with the indicate ratio of 1.51 / 1 tapped on the brand new upper unit.

Again, there is no 1.51 gear ratio for a DP. The 1.51 is for a single prop.

For 1 ujoint shaft revolution, the propeller made a little (very little) more than 0.5 revolution.

Sounds to me like the drive is a 2.32 drive for a V6.
Really the wrong drive for a 454. You need to find a drive with a 1.78:1 gear ratio.

 

[bolbic33]

Re: King Cobra swap to Sx Dps , what ratio and propellers set ?

HI Don,

i've already realized it was a single prop upper unit.
I'm a little bit disappointed because this drive is a bargain for the price ( Eur 1000)

Can i change the lower unit gears to reach a better ratio ?
Can i put my King Cobra 1/43 lower unit on it to have a simple SX matching my 454 ?

...or i just need to forget about this drive ... ?


THanks !

Bolbic