SeaRay 19 BowRider - Which Propeller To Use

[Per T]

I live In Norway where SeaRay boats are very rare (expensive), and therefor not so many to ask..
Boat : SeaRay weight ++ 1300 Kg - Motor : OMC Cobra V6 175 Hk. Sterndrive : Volvo Penta SX 2.18 : 1. Bought a used VP - SX to get rid of the micro switches and shitty gear changes...
How do I get the most speed out of this.? Do I have to change Ratio on the sterndrive.?
Hope someone can read my English and give me answer I can use to get a top boat summer .

 

[Lou C]

the original gear ratio with the V6 would have been about 1.60:1, so what you have is probably from a 4 cyl application. That will limit top speed but the acceleration on plane should be quite fast. The standard prop with the V6 Cobra was 14.5x19 or 15x17 depending on the size and weight of the boat. Due to the gear ratio you have you could probably go to least a 21 pitch.
Ideally you would have had a 1.60 :1 ratio like the original Cobra did. That's what I have on mine, but because the boat is so much bigger I use a 15x17 or a 15.5x15 depending on what we are using it for.
PS if the mechanic knows what they are doing, the Cobra shifts very well. I've had this one 18 years and learned how to set up the shift cable and switches. I considered the Volvo conversion which is a good option but was able to make the Cobra work so well I just kept it. Decent Cobra drives can be bought on ebay for about $1000 USD whereas Volvo SXs are between $2500 and $3000. Good if you can't get a mechanic to work on the Cobra.

 

[Per T]

the original gear ratio with the V6 would have been about 1.60:1, so what you have is probably from a 4 cyl application. That will limit top speed but the acceleration on plane should be quite fast. The standard prop with the V6 Cobra was 14.5x19 or 15x17 depending on the size and weight of the boat. Due to the gear ratio you have you could probably go to least a 21 pitch.
Ideally you would have had a 1.60 :1 ratio like the original Cobra did. That's what I have on mine, but because the boat is so much bigger I use a 15x17 or a 15.5x15 depending on what we are using it for.
PS if the mechanic knows what they are doing, the Cobra shifts very well. I've had this one 18 years and learned how to set up the shift cable and switches. I considered the Volvo conversion which is a good option but was able to make the Cobra work so well I just kept it. Decent Cobra drives can be bought on ebay for about $1000 USD whereas Volvo SXs are between $2500 and $3000. Good if you can't get a mechanic to work on the Cobra.

Thank You for the quick answer.
The reason I swapped my stern is that It`s not "natural" for a V6 Engine to go so low on RPM. I did`nt like to compromise and loose some effekt at top, just so the Engine did`nt stop..You right, I think my SX came with a 4cyl. diesel engine...The VP - SX can take 15" diam. What PITCH is best.? High = Best.?
3 or 4 blade Steel ? I have no idea on this subject..

 

[Bondo]

Thank You for the quick answer.
The reason I swapped my stern is that It`s not "natural" for a V6 Engine to go so low on RPM. I did`nt like to compromise and loose some effekt at top, just so the Engine did`nt stop..You right, I think my SX came with a 4cyl. diesel engine...The VP - SX can take 15" diam. What PITCH is best.? High = Best.?
3 or 4 blade Steel ? I have no idea on this subject..

Ayuh,.... Welcome Aboard,....... The answer to yer question is,....

Whatever pitch that allows the motor to run at 4800/ 4900 rpms, at Wot,.....

 

[Lou C]

Correct you may have to experiment to find the right one; if you can find a shop that deals in propellers that can lend a few different pitch props that you can try out, otherwise it gets expensive. I started with a 14.5x19 (too low, 4500 ), went to a 15x17 (better 4700 rpm), and wound up with a 15.5x15 (4900 rpm). With your drive ratio you will have to go a bit higher on the pitch.

 

[Per T]

What`s best : Biggest diameter and correct the RPM. with lower Pitch or to get the highest Pitch with lowest diameter ?? Does the Pitch give higher speed than going for bigger diameter on the propeller ? I am beginning to understand the propeller issue..your way to tell me and some reading on different web sites are giving me the inputs I need. So again : thank you for helping me understand what to look for . .

 

[Bondo]

Ayuh,..... Diameter is determined by blade design,......

Pitch pushes yer boat,......

You shop for pitch,....
The design engineer builds in the diameter to work with the blade design,......

 

[Per T]

Thank you for your answer..Now I`ll go "hunting" for my new propeller.! Hope
my asking in English was understandable because I certanly will use your knowledge again when (not if) I`m stuck in the future..Bye, for now

 

[Bondo]

Ayuh,...... Yer english is just fine, 'n we'll be here later,....