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Author Topic:   Correct Propeller for 30-HP on 13-footer

John from Madison CT posted 05-07-2009 07:26 AM ET (US)
From what I've read [the correct propeller for a 30-HP outboard on a 13-foot Boston Whaler is] the 10"x13". Correct? I'm re-powering my 1965 13-footer with a 1993 30-HP I'm buying locally. It was a bear finding a short saft, with electric start and remote steer, but I got lucky. I have an older 20hp on her now and it's tired, and really needs work that isn't worth spending.
Anyone have a 10"x13" kicking around they want to sell?
Peter posted 05-07-2009 08:06 AM ET (US)
I assume its an Evinrude or Johnson 30 (perfect motor for the 13 in my opinion). If that is right, a 10D x 13P propeller would be appropriate.
John from Madison CT posted 05-07-2009 09:41 AM ET (US)
Yep, a Johnson.
Peter posted 05-07-2009 09:58 AM ET (US)
Probably not too relevant anymore, but originally when that 2-cylinder 31.8 cubic inch engine platform came out it had a numerically lower gear ratio and the 10 x 11 (general purpose)and 10 x 13 (light load, speed) propellers would work for a 35 HP model on a 13 foot Whaler. The 1977 Evinrude 35 on my 13 Whaler was able to turn the 10 x 13 lightly loaded. We used the 10 x 11 for water skiing. At some point in the 1980s I believe, they raised the numerical gear ratio (might be at the time they whent to slightly different gearcase design with water intakes moved backwards), such that the 10 x 13 became the general purpose prop instead of the 10 x 11. Thus, it makes me wonder whether a late 1980s or 1990s 30 on a 13 foot Whaler can turn a 10 x 15 if lightly loaded.
John from Madison CT posted 05-07-2009 10:34 AM ET (US)
Peter: I'll let you know. The used engine I'm buying has the 10x15 on it now and before I spend any money, I want to check to see if this one will work OK.
My primary purpose of the boat is to take the kids tubing, almost always one at a time, but they're not 60lbs anymore either.
Tohsgib posted 05-07-2009 11:35 AM ET (US)
10x15 will work but only solo. Any weight and she will be a dog. 10x13 is the prop.
Peter posted 05-07-2009 11:55 AM ET (US)
If tubing is the purpose, the 10 x 13 will probably be better although I don't think tubes are that difficult to pull since they usually skim on the water. As a 120 lb or so teenager, I used to be able to get up and slalom water ski behind my 13 with the Evinrude 35 turning a 10 x 13.
John from Madison CT posted 05-07-2009 07:41 PM ET (US)
Thanks guys. I'll have to hunt down a used 13" pitch.
R T M posted 05-07-2009 10:27 PM ET (US)
Don`t want to change the topic to another engine but I`m running a '08 4 stroke 25 Merc/Tohatsu on my 13 footer. I`m running a 10 3/8x11 aluminum prop, and getting over the hump is real slow,although top end is 30mph at 5400rpm. Ive got it jacked up to where the plate is about 1/4 to 1/2" above the water on plane. Engine is on a 6" setback adjustable bracket. If I drop it down to where the plate is on or below the surface it really runs like a dog, and top rpm is 5000rpm. What do you think if I go to a nine inch dia. prop, and keep the plate at surface level. Maybe its just hard for me to get used of the lack of torque with a 4 stroke
Kind of wish I had one of those 31.8 cu. in OMCs
BTW those motors will run 50+mph on a GT Pro tunnel hull with a fishing lower unit too.
http://www.dillon-racing.com/about-the-plans.htm
rich/Binkie
Peter posted 05-08-2009 07:23 AM ET (US)
Thanks for that link. The sound in that video clip of the 31.8 2-cylinder continuously wound up at WOT brings back fond memories of the old 13 foot Whaler with the 1977 Evinrude 35 which had two speeds, idle and WOT, mostly WOT! :)
I think its just a lack of torque thing. No 4-stroke is going to match the power curve of a 2-stroke of similar displacement.
John from Madison CT posted 05-27-2009 02:37 PM ET (US)
OK,finally took the boat out for a ride today.
I got 25.5mph with me alone in the boat, a 6 gal tank of fuel and a battery. The prop is the 10"x15".
I'll have to figure out if the engine is turning full RPM's, but that being said, it jumped up on plane very quickly !!
Any comments, suggestions etc etc...
Tohsgib posted 05-28-2009 10:01 AM ET (US)
Read my above post...10x13 and she should see closer to 30.
John from Madison CT posted 05-28-2009 09:26 PM ET (US)
I'll have to track down a 10x13" pitch prop..
pcrussell50 posted 05-29-2009 03:54 AM ET (US)
Re: Hosepower and torque...
Horsepower is just an arithmetical manipulation of torque. To wit:
hp = torque x rpm/5252
So, if you know the torque at any given rpm, you also know the horsepower...and the converse as well. If your motor produces 35hp at, say, 5500rpm, you know that it's producing 33'ish lbsft of torque at that same point.
In fact, if you ever get a chance to view a graph produced by a testing facility that uses a dynamometer to test engine torque, [horsepower], torque and horsepower are ALWAYS equal at 5252 rpms. This applies to every engine in the world, ever made, that is capable of reaching 5252 rpm's.
Now on to practical application. Since 2-strokes have a power stroke every revolution, and 4-strokes have a power stroke every other revolution, two strokes, on paper, have twice the power for a given displacement. Of course, in reality, 4-strokes have the benefit of being able to have camshafts and valves, and to run higher compression ratios, so the power-to-displacement disparity is not really double.
So, when we say that 2-strokes have more torque than 4-strokes, well? Sure they do, if both have the same displacement. BUT, in the outboard world, we're not usually looking at displacement, we buy our engines based on horsepower. So, if we were to compare the torque curves of a 35hp two-stroke and a 35hp 4-stroke, I'd bet good money that the 4-stroke would produce more torque, earlier in the rpm range than the 2-stroke, simply because it MUST have more displacement in order to be able to produce the same power.
Can you tell I like engines? I dabble in a little amateur sports car racing, and out of economic neccessity, I build my own engines.
-Peter
John from Madison CT posted 06-11-2009 03:01 PM ET (US)
I still haven't replaced the prop on this boat with a 13" pitch, but I trimmed the engine out two holes (now at second to last) and I gained 3mph !
She's now doing 28mph. Pretty darn quick if I say so myself.
dg22 posted 06-11-2009 03:15 PM ET (US)
"but I trimmed the engine out two holes (now at second to last) and I gained 3mph !
She's now doing 28mph. Pretty darn quick if I say so myself."
Mine runs best at that tilt hole too.
Dave
skred posted 06-16-2009 12:24 AM ET (US)
I have my '97 30 Evinrude trimmed out to the 4th hole (2nd from the farthest), and with close to 400 lbs of humans, and another couple hundred in fuel, battery, gear, etc. - she gps'd at 28.8, and I still had a bit of throttle left... I don't think I want to go much faster in that size boat....
John from Madison CT posted 06-18-2009 07:23 PM ET (US)
Skred: Do you have a 13" pitch prop?
Tohsgib posted 06-19-2009 10:49 AM ET (US)
John just go buy one...$70? Should be plenty on E-Bay. I have one but not sure if my 11' will need an 11 or 13 so I don't want to sell just yet.
Tohsgib posted 06-19-2009 12:38 PM ET (US)
http:/ / cgi. ebay. com/ ebaymotors/ NEW-BLACK-3-BLADE-PROP-PROPELLER-10 -X-13-176191_W0QQcmdZViewItemQQ_trkparmsZ65Q3a1Q7c66Q3a2Q7c39Q3a1Q7c240Q 3a1318Q7c301Q3a1Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZit em2ea60c4e1bQQitemZ200354319899QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear
skred posted 06-19-2009 03:14 PM ET (US)
Yes my prop is a 13 pitch 4-blade aluminum. Doin't know the brand....
John from Madison CT posted 06-21-2009 08:44 AM ET (US)
Tosh Can you tell if this is an OMC prop by the model #?
Thanks for finding that too.

John
Austin Whaler posted 06-22-2009 01:08 AM ET (US)
My old 13' Whaler would do 31.4 with just me and a little gear, running a 10x15 aluminum prop 2nd to last hole out. With one other person, I had to bring the motor in one hole. This would decrease the speed to 30, but get this. The prop had 1 blade bent backwards for the last 1" 1/2, 1 blade with the last 1/3 of it gone, and the last blade with the last 1/3 of it bent back. (The motor came like this). I was very happy with it. The motor was an 1986 Evinrude 30 hp. I later changed the prop to a 10x15 aluminum that was badly pitted. The performance stayed the same, but the prop looked better. (I couldn't beat the price...free)
Hope it helps,
Austin
Tohsgib posted 06-22-2009 11:57 AM ET (US)
Count the splines. I only know of one engine that a 10x13 is made for.
John from Madison CT posted 07-13-2009 08:53 AM ET (US)
OK, just an update. I put a 13" pitch prop on the 30hp..
I don't know how many more RPM's I picked up as I don't have a Tach, but I did pick up around 1.5mph.(now 30mph with me alone, light load)
However, the real difference was is dragging the kids around on a tube. It worked much better than the 15" pitch. More hole shot and a lot less bogging down during hard turns.
west river rat posted 07-14-2009 10:29 PM ET (US)
John,
I run a 10x 13 on a 35 hp 13 whaler out of guilford (to the west of you) with the motor on its top most trim setting with out any battery and 6 gallons of gas forward of the front thwart. i can run 35 mph on flat water and still have plenty of hole shot. Your 30 is the same powerhead, just propshaft rated instead of powerhead rated with the lower gear ratio. you should be able to trim it up that last hole and gain more knots. see you on the water.

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Author	Topic: Correct Propeller for 30-HP on 13-footer
John from Madison CT	posted 05-07-2009 07:26 AM ET (US) From what I've read [the correct propeller for a 30-HP outboard on a 13-foot Boston Whaler is] the 10"x13". Correct? I'm re-powering my 1965 13-footer with a 1993 30-HP I'm buying locally. It was a bear finding a short saft, with electric start and remote steer, but I got lucky. I have an older 20hp on her now and it's tired, and really needs work that isn't worth spending. Anyone have a 10"x13" kicking around they want to sell?
Peter	posted 05-07-2009 08:06 AM ET (US) I assume its an Evinrude or Johnson 30 (perfect motor for the 13 in my opinion). If that is right, a 10D x 13P propeller would be appropriate.
John from Madison CT	posted 05-07-2009 09:41 AM ET (US) Yep, a Johnson.
Peter	posted 05-07-2009 09:58 AM ET (US) Probably not too relevant anymore, but originally when that 2-cylinder 31.8 cubic inch engine platform came out it had a numerically lower gear ratio and the 10 x 11 (general purpose)and 10 x 13 (light load, speed) propellers would work for a 35 HP model on a 13 foot Whaler. The 1977 Evinrude 35 on my 13 Whaler was able to turn the 10 x 13 lightly loaded. We used the 10 x 11 for water skiing. At some point in the 1980s I believe, they raised the numerical gear ratio (might be at the time they whent to slightly different gearcase design with water intakes moved backwards), such that the 10 x 13 became the general purpose prop instead of the 10 x 11. Thus, it makes me wonder whether a late 1980s or 1990s 30 on a 13 foot Whaler can turn a 10 x 15 if lightly loaded.
John from Madison CT	posted 05-07-2009 10:34 AM ET (US) Peter: I'll let you know. The used engine I'm buying has the 10x15 on it now and before I spend any money, I want to check to see if this one will work OK. My primary purpose of the boat is to take the kids tubing, almost always one at a time, but they're not 60lbs anymore either.
Tohsgib	posted 05-07-2009 11:35 AM ET (US) 10x15 will work but only solo. Any weight and she will be a dog. 10x13 is the prop.
Peter	posted 05-07-2009 11:55 AM ET (US) If tubing is the purpose, the 10 x 13 will probably be better although I don't think tubes are that difficult to pull since they usually skim on the water. As a 120 lb or so teenager, I used to be able to get up and slalom water ski behind my 13 with the Evinrude 35 turning a 10 x 13.
John from Madison CT	posted 05-07-2009 07:41 PM ET (US) Thanks guys. I'll have to hunt down a used 13" pitch.
R T M	posted 05-07-2009 10:27 PM ET (US) Don`t want to change the topic to another engine but I`m running a '08 4 stroke 25 Merc/Tohatsu on my 13 footer. I`m running a 10 3/8x11 aluminum prop, and getting over the hump is real slow,although top end is 30mph at 5400rpm. Ive got it jacked up to where the plate is about 1/4 to 1/2" above the water on plane. Engine is on a 6" setback adjustable bracket. If I drop it down to where the plate is on or below the surface it really runs like a dog, and top rpm is 5000rpm. What do you think if I go to a nine inch dia. prop, and keep the plate at surface level. Maybe its just hard for me to get used of the lack of torque with a 4 stroke Kind of wish I had one of those 31.8 cu. in OMCs BTW those motors will run 50+mph on a GT Pro tunnel hull with a fishing lower unit too. http://www.dillon-racing.com/about-the-plans.htm rich/Binkie
Peter	posted 05-08-2009 07:23 AM ET (US) Thanks for that link. The sound in that video clip of the 31.8 2-cylinder continuously wound up at WOT brings back fond memories of the old 13 foot Whaler with the 1977 Evinrude 35 which had two speeds, idle and WOT, mostly WOT! :) I think its just a lack of torque thing. No 4-stroke is going to match the power curve of a 2-stroke of similar displacement.
John from Madison CT	posted 05-27-2009 02:37 PM ET (US) OK,finally took the boat out for a ride today. I got 25.5mph with me alone in the boat, a 6 gal tank of fuel and a battery. The prop is the 10"x15". I'll have to figure out if the engine is turning full RPM's, but that being said, it jumped up on plane very quickly !! Any comments, suggestions etc etc...
Tohsgib	posted 05-28-2009 10:01 AM ET (US) Read my above post...10x13 and she should see closer to 30.
John from Madison CT	posted 05-28-2009 09:26 PM ET (US) I'll have to track down a 10x13" pitch prop..
pcrussell50	posted 05-29-2009 03:54 AM ET (US) Re: Hosepower and torque... Horsepower is just an arithmetical manipulation of torque. To wit: hp = torque x rpm/5252 So, if you know the torque at any given rpm, you also know the horsepower...and the converse as well. If your motor produces 35hp at, say, 5500rpm, you know that it's producing 33'ish lbsft of torque at that same point. In fact, if you ever get a chance to view a graph produced by a testing facility that uses a dynamometer to test engine torque, [horsepower], torque and horsepower are ALWAYS equal at 5252 rpms. This applies to every engine in the world, ever made, that is capable of reaching 5252 rpm's. Now on to practical application. Since 2-strokes have a power stroke every revolution, and 4-strokes have a power stroke every other revolution, two strokes, on paper, have twice the power for a given displacement. Of course, in reality, 4-strokes have the benefit of being able to have camshafts and valves, and to run higher compression ratios, so the power-to-displacement disparity is not really double. So, when we say that 2-strokes have more torque than 4-strokes, well? Sure they do, if both have the same displacement. BUT, in the outboard world, we're not usually looking at displacement, we buy our engines based on horsepower. So, if we were to compare the torque curves of a 35hp two-stroke and a 35hp 4-stroke, I'd bet good money that the 4-stroke would produce more torque, earlier in the rpm range than the 2-stroke, simply because it MUST have more displacement in order to be able to produce the same power. Can you tell I like engines? I dabble in a little amateur sports car racing, and out of economic neccessity, I build my own engines. -Peter
John from Madison CT	posted 06-11-2009 03:01 PM ET (US) I still haven't replaced the prop on this boat with a 13" pitch, but I trimmed the engine out two holes (now at second to last) and I gained 3mph ! She's now doing 28mph. Pretty darn quick if I say so myself.
dg22	posted 06-11-2009 03:15 PM ET (US) "but I trimmed the engine out two holes (now at second to last) and I gained 3mph ! She's now doing 28mph. Pretty darn quick if I say so myself." Mine runs best at that tilt hole too. Dave
skred	posted 06-16-2009 12:24 AM ET (US) I have my '97 30 Evinrude trimmed out to the 4th hole (2nd from the farthest), and with close to 400 lbs of humans, and another couple hundred in fuel, battery, gear, etc. - she gps'd at 28.8, and I still had a bit of throttle left... I don't think I want to go much faster in that size boat....
John from Madison CT	posted 06-18-2009 07:23 PM ET (US) Skred: Do you have a 13" pitch prop?
Tohsgib	posted 06-19-2009 10:49 AM ET (US) John just go buy one...$70? Should be plenty on E-Bay. I have one but not sure if my 11' will need an 11 or 13 so I don't want to sell just yet.
Tohsgib	posted 06-19-2009 12:38 PM ET (US) http:/ / cgi. ebay. com/ ebaymotors/ NEW-BLACK-3-BLADE-PROP-PROPELLER-10 -X-13-176191_W0QQcmdZViewItemQQ_trkparmsZ65Q3a1Q7c66Q3a2Q7c39Q3a1Q7c240Q 3a1318Q7c301Q3a1Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZit em2ea60c4e1bQQitemZ200354319899QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear
skred	posted 06-19-2009 03:14 PM ET (US) Yes my prop is a 13 pitch 4-blade aluminum. Doin't know the brand....
John from Madison CT	posted 06-21-2009 08:44 AM ET (US) Tosh Can you tell if this is an OMC prop by the model #? Thanks for finding that too. John
Austin Whaler	posted 06-22-2009 01:08 AM ET (US) My old 13' Whaler would do 31.4 with just me and a little gear, running a 10x15 aluminum prop 2nd to last hole out. With one other person, I had to bring the motor in one hole. This would decrease the speed to 30, but get this. The prop had 1 blade bent backwards for the last 1" 1/2, 1 blade with the last 1/3 of it gone, and the last blade with the last 1/3 of it bent back. (The motor came like this). I was very happy with it. The motor was an 1986 Evinrude 30 hp. I later changed the prop to a 10x15 aluminum that was badly pitted. The performance stayed the same, but the prop looked better. (I couldn't beat the price...free) Hope it helps, Austin
Tohsgib	posted 06-22-2009 11:57 AM ET (US) Count the splines. I only know of one engine that a 10x13 is made for.
John from Madison CT	posted 07-13-2009 08:53 AM ET (US) OK, just an update. I put a 13" pitch prop on the 30hp.. I don't know how many more RPM's I picked up as I don't have a Tach, but I did pick up around 1.5mph.(now 30mph with me alone, light load) However, the real difference was is dragging the kids around on a tube. It worked much better than the 15" pitch. More hole shot and a lot less bogging down during hard turns.
west river rat	posted 07-14-2009 10:29 PM ET (US) John, I run a 10x 13 on a 35 hp 13 whaler out of guilford (to the west of you) with the motor on its top most trim setting with out any battery and 6 gallons of gas forward of the front thwart. i can run 35 mph on flat water and still have plenty of hole shot. Your 30 is the same powerhead, just propshaft rated instead of powerhead rated with the lower gear ratio. you should be able to trim it up that last hole and gain more knots. see you on the water.