lorneparker1
Banned
How do you know if a new prop would benefit you or not? How does the pitch effect the preformance?
Lorne
Lorne
New prop Question
- Thread starter lorneparker1
- Start date
trendsetter
Active Member
Hey Lorne,
Prop pitch is the theoretical distance that the prop would travel in one revolution if it was in a solid. Think of it as a screw and the pitch is how far the screw would go into a piece of wood with one complete turn of the screwdriver. A 17" pitch prop would travel 17" in one complete revolution.
A prop is the single gear on an outboard/outdrive that can be easily changed. Changing to a higher pitch prop is like changing to a higher gear. i.e. a 15p prop to a 17p prop is similar to shifting from 1st gear to 2nd gear in effect.
Increasing pitch will increase the speed your boat can travel at any given RPM. So a 15p prop might move your boat 20mph at 3000RPM while a 17p prop might move the boat 23mph at the same 3000RPM. It doesn't always work that way because different prop designs are meant for different boats. When you put a prop on that is too high of pitch for your setup the prop will "slip" excessively in the water and won't produce the rated amount of pitch. i.e. a prop with higher pitch will not always make you go faster if it's the wrong prop for your boat.
The best simple rule for choosing a prop is to select on that allows your motor to turn at or near it's maximum rated RPM at wide open throttle. So if your motor is rated for 5000-6000 RPM maximum then you want a prop that allows your motor to turn near the top of that range. (5500-6000RPM at full throttle). If you haven't done so already you should test your current setup and find out what RPM you can achieve at WOT and what pitch and model your current prop is. This will tell you if you have the correct prop for your boat right now and what you should replace it with.
If you can find post the make/model/year of your motor(s) and your current prop and WOT RPM I can help you to choose a prop for your boat. I have been working with props for years and have a lot of experience in the area.
Hope that helps.
Cheers
Prop pitch is the theoretical distance that the prop would travel in one revolution if it was in a solid. Think of it as a screw and the pitch is how far the screw would go into a piece of wood with one complete turn of the screwdriver. A 17" pitch prop would travel 17" in one complete revolution.
A prop is the single gear on an outboard/outdrive that can be easily changed. Changing to a higher pitch prop is like changing to a higher gear. i.e. a 15p prop to a 17p prop is similar to shifting from 1st gear to 2nd gear in effect.
Increasing pitch will increase the speed your boat can travel at any given RPM. So a 15p prop might move your boat 20mph at 3000RPM while a 17p prop might move the boat 23mph at the same 3000RPM. It doesn't always work that way because different prop designs are meant for different boats. When you put a prop on that is too high of pitch for your setup the prop will "slip" excessively in the water and won't produce the rated amount of pitch. i.e. a prop with higher pitch will not always make you go faster if it's the wrong prop for your boat.
The best simple rule for choosing a prop is to select on that allows your motor to turn at or near it's maximum rated RPM at wide open throttle. So if your motor is rated for 5000-6000 RPM maximum then you want a prop that allows your motor to turn near the top of that range. (5500-6000RPM at full throttle). If you haven't done so already you should test your current setup and find out what RPM you can achieve at WOT and what pitch and model your current prop is. This will tell you if you have the correct prop for your boat right now and what you should replace it with.
If you can find post the make/model/year of your motor(s) and your current prop and WOT RPM I can help you to choose a prop for your boat. I have been working with props for years and have a lot of experience in the area.
Hope that helps.
Cheers
Halilogger
Active Member
I posted a thread on props a while back, there is probably some helpful info on that thread.
There are other factors you need to consider as well.... will you be running with heavy loads ? is your hole shot important ? do you do a lot of cruising ? Aluminum or Stainless ? these 2 prop materials offer different advantages.
There are other factors you need to consider as well.... will you be running with heavy loads ? is your hole shot important ? do you do a lot of cruising ? Aluminum or Stainless ? these 2 prop materials offer different advantages.
Whole in the Water
Well-Known Member
Prop Material Pros and Cons:
Stainless Steel
Pros: better overall performance, (higher top speed, slightly better fuel economy), more durable, stronger material.
Cons: more expensive. If you dont have a break away hub if you hit something you can transfer the energy up into leg and damage it.
Aluminum
Pros: Cheaper, Will bend or break easier before transfer of energy up into leg.
Cons: poorer acceleration, lower top speed, less durable
Stainless Steel
Pros: better overall performance, (higher top speed, slightly better fuel economy), more durable, stronger material.
Cons: more expensive. If you dont have a break away hub if you hit something you can transfer the energy up into leg and damage it.
Aluminum
Pros: Cheaper, Will bend or break easier before transfer of energy up into leg.
Cons: poorer acceleration, lower top speed, less durable
Whole in the Water
Well-Known Member
Propellers incorporate a cup at the trailing edge of the propeller blade. This curved lip on the propeller allows it to get a better bite on the water. This results in reduced ventilation, slipping, and allows for a better hole shot in many cases. A cupped propeller also works very well where the motor can be trimmed so that the propeller is near the surface of the water. The cup will typically result in higher top end speed on one of these applications.
lorneparker1
Banned
SO i guess the first thing i need is a tack. lol. I havea 16.5 welded HEAVY boat. and a 75 4 stroke 2007 yammy on it. it does 35 mph with just me in it.I will get a tack installed and go from there. thanks folks!
Seafever
Well-Known Member
While we are on the subject of props may I ask a question........
If you have a kicker that is "too fast" in the water at LOW rpm for trolling....do you go to a lower pitch prop to slow it down or do you go higher pitch.
I have a a kicker that always seems to be pushing the boat too fast at low throttle and can't seem to dial it in anyhow for the speed I like. I thought if i went to a different pitch prop I could control it that way.
What would you suggest?
Thanks.....
If you have a kicker that is "too fast" in the water at LOW rpm for trolling....do you go to a lower pitch prop to slow it down or do you go higher pitch.
I have a a kicker that always seems to be pushing the boat too fast at low throttle and can't seem to dial it in anyhow for the speed I like. I thought if i went to a different pitch prop I could control it that way.
What would you suggest?
Thanks.....
trendsetter
Active Member
Lower pitch prop will allow you to go slower at idle (and all through the RPM range).
The yamaha "High-thrust" model kickers have a lower gear ratio than regular motors. That is why they have higher thrust. The exact same this can be accomplished by getting a prop with a lower pitch.
Try to find a 4-blade lower pitch prop and you should have better control at low speeds, better reverse thrust and a slower trolling speed.
Cheers
Halilogger
Active Member
Seafever take your kicker prop off and take it to a propeller shop and they should be able to reduce your pitch on that prop by 1 to 2 degrees.
I think prop pitch is not going to solve a problem such as too fast a troll. Let`s assume he is now trolling at 3.3 mph and wants to slow to 2.2 mph, That is a 1/3 reduction in speed which means that a 17 pitch prop would have to change to a 12 or 13 pitch to accomplish it. Because prop pitch is a measurement of inches travelled for each revolution that directly relates to speed.
Charlie
Well-Known Member
A lower pitch "may" or "may not" help? Without knowing the size of kicker? I would suggest a smaller kicker!
Lowering the pitch (and diameter) will reduce amount of water going through the prop just like that screw described. Lower pitch will produce more thrust and reduce top end speed - has to; however, it may or may not effect forward "trolling" speed of a boat enough to really matter? That has more to do than just pitch and diameter of the prop. You have to look at length, beam, and especially WEIGHT; along with hull design, RPM, water conditions, etc, etc. Don’t think so, put a T9.9 on a 10' Zodiac and see how fast it will go... then on a 40 foot sailboat... then stick it on the back end of an aircraft carrier and see how fast it pushes that! Bet it moves the Zodiac faster!
That is why they do all those performance tests! If you choose to decrease the pitch (or diameter) of a prop, you still need to make sure you stay within manufacturer guidelines.
Last edited by a moderator:
Halilogger
Active Member
Also if you lower your pitch and diameter to much you will lose maneuverability in the wind and slow steering response which would suck as much as trolling to fast.
Whole in the Water
Well-Known Member
Yyou could try to slow your trolling speed down a bit an 'old school' way - by dragging a 5 gal. bucket behend you. Pretty simple and cheap.
lorneparker1
Banned
ok, so i got a tach installed. and i am running at 4900 at WOT. it says i should be running 5000-6000. That seems like a big gap, do i want to be closer to 6k or am i ok at 4900>? if not what should i do.
Lorne
Lorne
Kristo
Active Member
Lorne it looks like you are slightly over-propped ...your prop is taking too big a bite every time it turns
If you tried a finer pitch you would find that your hole shot would improve and your engine would reach the recommended WOT RPMs.
You will probably find that you lose a little top speed however you would notice that you get on step quicker especially with heavier loads.
That being said I don't think you will damage anything by running the prop you have as you are very close to the reccomended 5000 rpm
If you tried a finer pitch you would find that your hole shot would improve and your engine would reach the recommended WOT RPMs.
You will probably find that you lose a little top speed however you would notice that you get on step quicker especially with heavier loads.
That being said I don't think you will damage anything by running the prop you have as you are very close to the reccomended 5000 rpm
Halilogger
Active Member
I would say say your to low on your rpm and unless your running light and doing mostly cruising, you will be putting more strain on your motor and leg. Ive heard all the rpm ranges you should meet min and max, and it seems to very depending on who you talk too. I run slightly over propped as well, i run long distances sometime 70 to 80 miles each way, but its just me and about 50lbs of gear. When I go to the west coast and have a few passengers I drop to my 19p.
You will probably have lower fuel costs if you drop your pitch, like Kristo says you will come out the hole much quicker.
You will probably have lower fuel costs if you drop your pitch, like Kristo says you will come out the hole much quicker.
Jencourt
Well-Known Member
Lorne,If you have read my thread on Similar subject then you will know where I am at on this prop thing. My motor says 5-6 5500-6000 being optimal. I went with 4 blade 17pitch and could only make 4900 as well. After talking to prop shops ,marine mechanics and of course this web site ,I am now going to test a same make and model of prop but in a 15 pitch. I will let you know how it affects things for me wen I get it tested.
Any way all the info I have received so far leads me to believe that it is best for the longevity of motor to make sure you can achieve recommended range and not lug motor by being over pitched.
Cheers:Ray
Charlie
Well-Known Member
For the size and weight of your boat - You are over propped!
Put a couple of people and their gear on board - You are really over propped!
IAW the manufacturer, if you run the boat and are within WOT guidelines, you are fine! You are NOT! I personally like and recommend running on the top side of that WOT range, with the boat configured with its normal weight (e.g. gas, people and gear). That way you add all those fish caught, you will still stay within guidelines.
For starters, go to a prop manufactures website like "Mercury" and but your information in their select a prop section. Pick out the kind of prop you are thinking of, as construction, number of blades, and pitch.
http://www.mercurymarine.com/propellers/prop-selector/#step1
You should be able to go directly to the boat manufacture website and download the performance tests for your individual boat. If you can't do that go directly to Yamaha website, look for "Persormance Bulletin Search" put in your information and look for your specifc boat - that will give you the specs, your boat should have.
http://www.yamaha-motor.com/outboard/products/perfbull.aspx
If the boat is not listed... not really a problem. Go to the the Yamaha website and just for for your engine specs. I believe, you will find max RPM is going to be 6000!
If you are wanting to stay with the same prop you currently have, I would suggest starting by dropping two pitch.
