Volvo gearset/prop what if??

[penbroke]

Since the Volvo 1.61 lowers are somewhat rare and expensive and the 2.15 lowers are cheap and plentiful has anyone considered using a big prop on a 2.15 lower?

I turn a pristine NOS Ultra 24p right around 5k rpm at 1.61:1 reduction. Based on what I have seen posted the recommended Solas would likely be a 21p (if I could turn it) because of the much lower slip.

What if I was to run a 25p Solas on a 2.15:1 lower or a 23p on a 1.89:1 lower? If you do the math the numbers are not as far off as you might expect.

I know this is not the optimum solution but can't help but wonder...

I just throw this up for discussion and as always, any input appreciated.


Frank
Looking for a lower.

[Lenny]

That's an interesting idea. :yes: The 2:15 and the 25P SOLAS might just be the ticket :)

[mattyboy]

they don't make a 25 p solas????

going from a 1.6 to a 2.1 would be a net gain of around 400-500 rpm. the 21 solas on your setup currently would be at around a 300-400 rpm loss.

the way to really go fast would be turning a 23 solas on a 1.3 ratio at 5000 rpm ;)

[BUIZILLA]

i'd try it.. :yes:

[penbroke]

they don't make a 25 p solas????

I thought there was a 21, 23 and a 25p that nobody had the ponies for...


Frank

[mattyboy]

19 21 23 that's all

[mrfixxall]

I think you will brake the prop loose and create more slip just my o2..im using a alpha drive in comparison now,years ago a friend had bought a chris craft scorpion but it was missing the drive..he came to me asking if i had a drive,i had a 1.9? drive from a 4cyl boat i aquired..the boat he had,had a 350 260 hp in it so i put the drive i had on it and a 23 yamaha prop..We took it out for a test run and believe ot or not the boat was pretty quick with the max speed of 62 mph(on speedo) it shocked me,about a month later he called my stating the boat wont go into gear,i took the top off and all the gears were distroyed..i guess to much hp and the 23 p prop was to much strain on the drive..

try it but keep a eye on drive temps:)

[penbroke]

they don't make a 25 p solas????
going from a 1.6 to a 2.1 would be a net gain of around 400-500 rpm. the 21 solas on your setup currently would be at around a 300-400 rpm loss.
the way to really go fast would be turning a 23 solas on a 1.3 ratio at 5000 rpm ;)

Top speed is not my goal. Never was. If I wanted to go fast I would get one of them boats with the side fuel fills.:wink: A top end of 55 is fine with me. There is no point in trying to push this old boat into high 60s. That's not what it's about and it's just not worth the coin to me. With the Ultra I can run 40-45 mph at a little over 3 gph all day with 35 gal on board. It's cheaper that going to the movies...

The lack of a 25p does put a damper on trying it.

Frank
I can't make your numbers work...

[penbroke]

I think you will brake the prop loose and create more slip just my o2..im using a alpha drive in comparison now,years ago a friend had bought a chris craft scorpion but it was missing the drive..he came to me asking if i had a drive,i had a 1.9? drive from a 4cyl boat i aquired..the boat he had,had a 350 260 hp in it so i put the drive i had on it and a 23 yamaha prop..We took it out for a test run and believe ot or not the boat was pretty quick with the max speed of 62 mph(on speedo) it shocked me,about a month later he called my stating the boat wont go into gear,i took the top off and all the gears were distroyed..i guess to much hp and the 23 p prop was to much strain on the drive..
try it but keep a eye on drive temps:)

Interesting... I would think the greater reduction would be harder on the bottom end until you went too fast for the bearings in the top.


Frank

[mattyboy]

Top speed is not my goal. Never was. If I wanted to go fast I would get one of them boats with the side fuel fills.:wink: A top end of 55 is fine with me. There is no point in trying to push this old boat into high 60s. That's not what it's about and it's just not worth the coin to me. With the Ultra I can run 40-45 mph at a little over 3 gph all day with 35 gal on board. It's cheaper that going to the movies...
Frank
I can't make your numbers work...


Frank then there's your answer ;) if it is good then why change


Fix it is very hard to get a solas to slip they are steady thru out their range around 7-8% slip. the best example is cutting the throttle hard from wot ti boat acts like someone thru out an anchor no squirrely no skidmarks it is like the boat had brakes

[mrfixxall]

boat acts like someone thru out an anchor no squirrely no skidmarks it is like the boat had brakes





Thats how my ultra's acts now that dah propellers fine tuned them:)

[mattyboy]

boat acts like someone thru out an anchor no squirrely no skidmarks it is like the boat had brakes
Thats how my ultra's acts now that dah propellers fine tuned them:)

how did it react before they tuned it???

[mrfixxall]

how did it react before they tuned it???


the boat felt like my drive had a stall converter in it. Blow planing,then bite then slip,back off throttle and hammer it then the rpop would bite again..it would freewheel when i let off..now with the 24 i can almost leave the water whyle going on plane..

[mattyboy]

the ultra I had would leave skidmarks

[mrfixxall]

mine now will slow down real fast but wount leave skid marks..

[penbroke]

Frank then there's your answer ;) if it is good then why change ...


Why change? The first sentence in the original post.

I posed the question to start a discussion on prop pitch and gearsets. The fact that Solas does not have a 25p on the shelf is not the point. I'm sure there are more than a couple prop guys that could pound another inch or two into a 23p. The specifics of my situation are not the point either. I use it only because it is the setup that I know best.

I am not looking for a specific answer. It wasn't really a specific question. Just a subject for discussion. I know it would not be the optimum solution as I stated in the first post. There are a lot of very smart and experienced folks here that are mostly quiet most of the timeon subjects like this. I was hoping to (and did) draw a few of them out into the open...


Frank

[mattyboy]

ok for the purpose of discussion

add an inch of pitch when crunching the numbers on the solas

i still stand by spin the prop once now do I want everything else all the spinning ,wurly,up and down parts to work twice has hard one and a half as hard or one and a third as hard for that one turn???

also the higher pitched solas don't like the 200 lower for some reason clearance to the anti cav plate is very tight jay's 200 lower didn't like the 21 so any lower change would need to be a 250 or newer but that is not a problem even jay has a 250 lower now looking to try a 21 solas

[penbroke]

You need to look at the entire drive train including the prop.

21p / 1.61 reduction gives 13.04 inches of travel per engine revolution.

23p / 1.89 reduction gives 12.17 inches of travel per engine revolution.

25p / 2.15 reduction gives 11.63 inches of travel per engine revolution.

The variance seems to be well within what one could do with a minor pitch change or adding a bit of cup.

Food for thought...


Frank

[MOP]

Frank you may just be on to something, usually a slower turning wheel is more efficient then a fast turning one. I know you have enough in your stash of goodies to give it a whirl!

[Lenny]

2:15 and a 25 is the ONLY thing that seems to give you 55. ( with no slip )

That 26 Ultra from a while back, and DAH propellors might get you close.

[mattyboy]

Frank
what slip ratio are you using ??? the solas is constant thru out it's range 7-8% so the faster you spin it the more ground and time you make up so I am not sure what props you are considering for this discussion but the ultra gets less effecient the faster you turn it


if you want to look at the big picture according to your numbers

a 21 on a 1.6 at 600 rpm idle will travel 70 feet further than the 25 p at 2.1 in one minute at 3000 rpm cruise it is just over a football field at 352.5 feet on a 10 minute jaunt that's well over a half a mile now take a 60 mile run ??

now let's talk gallon per hour burn and working harder to cover the same ground in the same time space continueum

yes moving the ratio is equal to changing pitch roughly a 200 rpm for each jump and moving up to a ratio that requires a big prop to keep the rpm in check and that has always been the problem with high hp volvo apps there are not alot of effecient high pitched volvo props around

for pratical purposes the solas are
20p
22p
24p

if you crunch the numbers at 19p 21p and 23p you get a negative slip number or prop grip ;)


dropping the ratio is more the key to me

[mattyboy]

using your numbers


all at 3000 rpm with a solas ( for sake of discussion they made a 25 pitch) using the 7% slip factor


the 25p at 2.1 30.7 mph
the 23p at 1.8 33.8 mph
the 21p at 1.6 34.7 mph
the 19 p at 1.3 38.6 mph


it not about speed but at 3000 rpm what would be your choice keeping fuel, time , engine hours and load???? with the lower ratio 1.3 and a 19 I can cruise the 30 mph at 2331 rpm with the 25p at 2.1 and that motor is turning 700 more rpms every minute for the same 30 mph


now what does the class think about if we go to the other end of the throttle band WOT say like 5000 rpm with the same solas and 7% slip

well let's just do it for the sake of the ones who go a little speed crazy here ;)

the 25p at 2.1 52.4mph
the 23p at 1.8 56.3mph
the 21 at 1.6 57.8mph
the 19p at 1.3 64.4mph

i dunno but i think I have an idea what my answer would be :yes:

my plan is getting a mill that can turn 5000 rpm with a 23 solas on the 1.3 250 I have :yippie: that would be moving right along up there where the 22 guys run

[penbroke]

If you throw out the 25p because it doesn't exist and the 1.38 lower because they are all but non-existant in the wild (Yes, I know you and Kenny picked one up. By accident as I recall...) that leaves the 23p at 1.89 and the 21p at 1.61.

If you believe that the slip numbers and the rotational drag both go up as the propellor rpms go up the 33.8 mph and the 34.7 mph don't seem quite so far apart anymore.

You seem to be proving my point. :wink:

Again, I know this is not the best solution. If it was, the industry would have evolved in this direction. It just might be a viable solution as the supply of parts for the Volvo drives slowly dry up. I think it would be interesting to try...


Frank :lookaroun:

[mattyboy]

the slip numbers go up with the ultra the solas stays the same

[mattyboy]

If you throw out the 25p because it doesn't exist and the 1.38 lower because they are all but non-existant in the wild (Yes, I know you and Kenny picked one up. By accident as I recall...) that leaves the 23p at 1.89 and the 21p at 1.61.
If you believe that the slip numbers and the rotational drag both go up as the propellor rpms go up the 33.8 mph and the 34.7 mph don't seem quite so far apart anymore.
You seem to be proving my point. :wink:
Again, I know this is not the best solution. If it was, the industry would have evolved in this direction. It just might be a viable solution as the supply of parts for the Volvo drives slowly dry up. I think it would be interesting to try...
Frank :lookaroun:


ok so if we agree that the 25 is out with the 2.1 and the 1.3 is out and the 1.6 lower are hard to find and expensive then your answer is the 1.8

like a 10 speed bike stuck in first gear be prepared to pedal alot

[Kirbyvv]

I hadn't realized the 1.6 ratio's were getting hard to find. Just checked ebay and holy @#$%&...expensive. I'm keeping my spare 280 as a long term investment.

[lordviper13]

being that my outdrive needs to be rebuilt and I was doing the ebay thing I had this same thought because it seems like 4 cyl units are a dime a dozen and probally were never really beat on that much

[mattyboy]

guys there is a volvo 200 for sale on craigslist in hacketstown nj came off a donzi most likely a 1.6 $450

[penbroke]

So... at 3000 rpm the difference is less than 1 mph. That works out to way less than 2 mph at 5000 rpm. It's like a 10 speed that won't go from 9th to 10th.

Again, (yes again,) it is NOT the ideal solution. I get that, really, I do...

However, it may be an increasingly viable solution as the supply of parts goes away... A future without old Donzis with Ford/Volvo power would be a lesser one. We lose a few every year...


Frank
I'm just sayin'...

[mattyboy]

So... at 3000 rpm the difference is less than 1 mph. That works out to way less than 2 mph at 5000 rpm. It's like a 10 speed that won't go from 9th to 10th.
Again, (yes again,) it is NOT the ideal solution. I get that, really, I do...
However, it may be an increasingly viable solution as the supply of parts goes away... A future without old Donzis with Ford/Volvo power would be a lesser one. We lose a few every year...
Frank
I'm just sayin'...


remember Frank my numbers are done witha constant slip number of a solas with an ultra or other prop you might have 10% slip at 3000 and 15% or more at 4500 and higher

[BigGrizzly]

I already have done this on DavidO's boat the 23 works on the 2.1, but it is the fragile one. The 23 has less slip then the 21. On my boat there is almost a 500 rpm drop, and cruise is up 10 MPH. Don't sell the Solas short. You can't compare it to any other prop.

[Rootsy]

You know Frank, those little 289's will take the RPM... Question is... will the drive... Just spin er on up there... :wink: