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Volvo penta duoprop selection
Posted: Fri Aug 17, 2018 11:23 pm
by Lazyboater
Hello
I'm new here and stumped on a subject.... Prop selection. I have a 94 200 with the 572 and 290 dp with 1.95 ratio. Right now I'm running B6 props and only getting about 44mph at wot. I'm thinking of going to B7's to get more speed. Any help will be thanked.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 8:39 am
by jhnmdahl
What rpm are you at with your current setup wide open?
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 8:40 am
by Big Block Power
We need to have your wide open throttle rpm to really help you. If you go up in prop pitch you may go faster or may go slower. Plus you will lose your hole shot. Unless your bouncing off a rev limiter you prob won't be gaining.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 9:32 am
by cmattj
Introduce yourself in the new members section. We’d like to hear about your Cobalt.. see some pics. Other members with your combo can chime in.
You may want to correct your engine description to a 5.7 although if it had a 572 we’d be wanting a ride!!
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 10:07 am
by Big Block Power
cmattj wrote: Sat Aug 18, 2018 9:32 am
Introduce yourself in the new members section. We’d like to hear about your Cobalt.. see some pics. Other members with your combo can chime in.
You may want to correct your engine description to a 5.7 although if it had a 572 we’d be wanting a ride!!
You got 5.7 out of that. Wow I missed that one. But I had no clue what engine it was. I'm like heck I would take a 520 but a 572 Volvo had it going on back then.
I'm sure he's sick of telling everyone thank you after they say that's a beautiful red boat. After he just spent 2 weeks buffing it.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 10:45 am
by cmattj
Big Block Power wrote: Sat Aug 18, 2018 10:07 am
I'm sure he's sick of telling everyone thank you after they say that's a beautiful red boat. After he just spent 2 weeks buffing it.
You get used to crowd gathering. I may change the name to simply..
“thank you”

Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 10:52 am
by Lazyboater
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Sorry, I'm new to boating just got a very good deal on the boat... wot is 4600 to 4800.... I didn't want to blow engine..lol. There are alot of things i need to do with this boat to make it right. But I will send pics of what $500 can get you in Texas. Engine is sound.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 11:03 am
by Big Block Power
Sweet. 5.7L 2 barrel carb. Is my guess.
Sounds like your right in line if that's what your hitting for rpm.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 11:04 am
by cmattj
Looks good and I like that it does say 572. Which is s sb Chevy 350ci convered to liters. 5.7 Adding a 2 barrel?? Cool cover!!
Yes more pics and we will determine if you should make a change.
Sounds right now and adding pitch will give you cruise speed but may strain on top end
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 11:31 am
by Lazyboater
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 1:16 pm
by NautiGirl
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 3:24 pm
by Big Block Power
Then you will need a new cowl. 574.



If your going to do that you mine as well change the cam. You could get in touch with nola's guys they would know which one to put in there. I would leave the valves alone you never know they could start to stick if you have a good but shotty machine shop do it.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 7:05 pm
by Lazyboater
But for now I want to know if anyone knows the difference of pitch in B6 props and B7 props.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 7:12 pm
by Big Block Power
Lazyboater wrote: Sat Aug 18, 2018 7:05 pm
But for now I want to know if anyone knows the difference of pitch in B6 props and B7 props.
Yea one pitch. lmao
It's like a mercury 24-26 pitch just in Volvo secret code.
200-300 rpms prob.
Re: Volvo penta duoprop selection
Posted: Sat Aug 18, 2018 7:36 pm
by cmattj
Big Block Power wrote: Sat Aug 18, 2018 7:12 pm
Yea one pitch. lmao
It's like a mercury 24-26 pitch just in Volvo secret code.
200-300 rpms prob.
Tricky Swedes