What prop do I need...

[SRXScott]

I just bought a 2003 Sea Ray 182 SRX with a 2005 4.3L Merc (190HP - original motor not winterized...)) and a 14.5/19 3 blade aluminum prop. My top end is 44mph empty but I was hoping to get another 3 or 4 mph without losing a quick holeshot. My tach at wot shows about 4300-4400 RPM and I'm thinking this is 300 rpm slower than it should (tac issue?). Any suggestions for a new prop (preferably aluminum 3 or 4 blade).

 

[nitrosteve]

Re: What prop do I need...

Yeah something could be off..

What is you drive ratio? 1.62

 

[SRXScott]

Re: What prop do I need...

yeah, I should have mentioned it's a 1.62 drive ratio.

 

[Bondo]

Re: What prop do I need...

My top end is 44mph empty but I was hoping to get another 3 or 4 mph without losing a quick holeshot. My tach at wot shows about 4300-4400 RPM and I'm thinking this is 300 rpm slower than it should (tac issue?).

Ayuh,... That ain't gonna happen,... You're already at/ over the peak horsepower....
That's why the rpms are topping out at 4400...
If anything, you could drop 2" of pitch, 'n see where the Wot rpms end up...

 

[SRXScott]

Re: What prop do I need...

so, a 17 or 18 inch pitch prop might help. Would switching to a 4 blade aluminum prop improve things?

 

[extreme76]

Re: What prop do I need...

Recommended WOT is 4400-4800, so you are at the bottom end (light loaded) if your tach is right. I show 8-10% slip, which is very good for a 3 blade aluminum prop on a stern drive. I suspect the MPH and/or tach may not be 100% accurate. If the above numbers are correct you would benefit from a lower pitch (particularly at heavier loads), however you probably will not get much more speed. As Bond-o noted the 4.3 reaches max horsepower at 4400 and your prop slip is already low, but once again that is assuming accurate numbers. If you are serious about improvement make sure that is GPS speed and verify your tach first.

 

[SRXScott]

Re: What prop do I need...

First of all, all this info is very helpful - as you can probably guess, I am new to this game. The 44mph/43-4400 RPM was GPSed and it was with me alone, on a nice calm lake with about 3/4 tank of gas (70 litres as we say up here in Ontario or about 20 gallons in US speak...). As for the tach a mechanic told me that on the trailer the motor sounds good and that it was hitting its peak RPM although the tach was showing 43-4400. I read a boat test of my exact boat and it topped out at 47mph - again not sure what prop was been used. Would I be best to go down to a 17 or 18 pitch and 3 or 4 blade prop for a little more speed?

 

[86 century]

Re: What prop do I need...

Your speeds are not to bad my old starcraft that is over powered by at least 50hp will only make 53-54.
I have been testing props all summer on three boats one of witch is a 206 rinker captiva with a 4.3(190hp) the best we can get out of it was 41.5 with a SS 19p turbo. However It is the most fun with a 25p high five will only run about 35 but has a great hole shot.
Good Luck

 

[extreme76]

Re: What prop do I need...

I wouldn't worry to much about the boat test at 47mph. I would guess it was with a SS prop, probably in cool dry air, flat water, etc... and your only talking 3 mph. Take yours out on a cool, dry fall morning and you probably will get 46 with what you have. I also have a 4.3l 190hp, but my boat is about 150 lbs lighter than yours. I can get 44 with a MW 21 pitch aluminum (1.81 ratio), 46 with SS.

 

[Tail_Gunner]

Re: What prop do I need...

I just bought a 2003 Sea Ray 182 SRX with a 2005 4.3L Merc (190HP - original motor not winterized...)) and a 14.5/19 3 blade aluminum prop. My top end is 44mph empty but I was hoping to get another 3 or 4 mph without losing a quick holeshot. My tach at wot shows about 4300-4400 RPM and I'm thinking this is 300 rpm slower than it should (tac issue?). Any suggestions for a new prop (preferably aluminum 3 or 4 blade).

Intresting boat you have there...It seems according to Nadas site that thing can run a 7 litre motor..its 2600lbs dry..Fairly light boat for such a large engine capacity.I need to look futher but if the site i looked at was correct your motor is @ the bottom end for power train area..You might be underpowered..A 19' boat with a healthy 4.3 should turn 50 plus...19@4300....18@4500....17@4700....16@4900........Somethings afoot..Tach off..non gps speed...Timing or carbs messed up...Or you are boating uphill....Umm maybe not

 

[raysprops]

Re: What prop do I need...

Are you taking into account the elevation of the lake you are running on as compared to where the prop test was done. A 1000 Ft. difference can really change the performance. Here in the Kelowna area I have a number of customers with compareable boats and most of them are getting perfomance similar to yours. Some of them are running Quicksilver 18P 4Bl. aluminium and find the hole shot is better without losing much top end, others have gone the 4 or 5 blade stainless route and say they are getting better all around perfomance. Most seem to find the best props are in the 17 to 19P range and that Mfg. and blade design do make adifference so you should see if anyone in your area has test props available.