When we in the USA talk mph it is Miles per hour not Knots per hour which is about 1.2X faster.
Yes, altitude does effect speed, so does tempature and humidity. What is your altitude?
MERC 14x11x3 prop report
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aya16
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Sheshad from the yamaha website it says you have a 2005 engine
4stroke fuel injection.
your rpms are in the ball park but your speed seems to be like your ballast is full. 12-14 mph is like ballast full. It sounds like prop slip but not sure. with the 14x11 at 6000 or even 5500 should be around 17mph
If I had to quess a 13x12 prop or even 13x13 would maybe work better.
I dont know if there is such a prop for your engine. Do you have the
yamaha big foot same as the merc? smaller pitch even with large ears
means slower speed if you can run more pitch at the same rpm you might be better off.
I dont know of anyone getting 22mph with a 50hp motor. My 50 suz in a heavy boat tops out at 17mph without ballast 14 with. I have (I think because the stamping is not clear) a 11.5x13 inch pitch prop.
if your engine is the same as the merc big foot maybe someone here with the same engine can help you.
4stroke fuel injection.
your rpms are in the ball park but your speed seems to be like your ballast is full. 12-14 mph is like ballast full. It sounds like prop slip but not sure. with the 14x11 at 6000 or even 5500 should be around 17mph
If I had to quess a 13x12 prop or even 13x13 would maybe work better.
I dont know if there is such a prop for your engine. Do you have the
yamaha big foot same as the merc? smaller pitch even with large ears
means slower speed if you can run more pitch at the same rpm you might be better off.
I dont know of anyone getting 22mph with a 50hp motor. My 50 suz in a heavy boat tops out at 17mph without ballast 14 with. I have (I think because the stamping is not clear) a 11.5x13 inch pitch prop.
if your engine is the same as the merc big foot maybe someone here with the same engine can help you.
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aya16
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shehzad another thought that might explain the drop in rpm's is did you use the right spark plugs? Dumb question I know but if you went from ngk to champion or the other way around or even have the wrong heat range it could drop your rpm. Try putting the old plugs back in and see if it makes a diff. I know you saved them we all do.....
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shehzad
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aya 16,
I am very happy to note that you also get maximum 17 mph with 50 hp but beleive me, I have read so many threads where 50 hp has acheived 22 mph. If people say so, I have no reason to deny.
You are also rigt, that spark plugs could make difference in rpm and thinking about that, I had also put back the old plugs, after cleaning them properly but the result was same. Although the plugs I changed were also spare plugs, came with the engine.
It is interesting to note that my YAMAHA 50T is actually 2005 model where as I imported this engine from Japan in 2006.
Now the point is, should I live with this 5500 rpm.
In future, if I could sell out my 50 hp engine, I would definately buy 90 hp engine. Problem is that there is not much possibility of finding a customer for 50 hp in my area.
I am very happy to note that you also get maximum 17 mph with 50 hp but beleive me, I have read so many threads where 50 hp has acheived 22 mph. If people say so, I have no reason to deny.
You are also rigt, that spark plugs could make difference in rpm and thinking about that, I had also put back the old plugs, after cleaning them properly but the result was same. Although the plugs I changed were also spare plugs, came with the engine.
It is interesting to note that my YAMAHA 50T is actually 2005 model where as I imported this engine from Japan in 2006.
Now the point is, should I live with this 5500 rpm.
In future, if I could sell out my 50 hp engine, I would definately buy 90 hp engine. Problem is that there is not much possibility of finding a customer for 50 hp in my area.
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Frank C
All of the powersailing Macs have a tendency to plane with the bow very high. It's common. Many owners mount the outboard with a wedge plate on the outside of transom. The wedge is thicker at the top, and permits the outboard to be "trimmed" past vertical. This places the prop farther under (closer to) the transom. When fully trimmed-in (or "under"), the prop force can help to slightly lower the bow-high attitude. A precise combination of prop and motor can make this a faster and maybe more efficient setup. Unfortunately, in Pakistan you probably won't find enough variety of props and parts to explore this option.
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aya16
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dont use the foils bow lift is normal part of getting on plane. the mac M will plane out at 15mph or so. the bow will come down some, but you dont want it to come down too much or it will nose dive into swells.
Frank is right about experimenting with diff props and such but being where you are it doesnt sound like you will have a lot of choices.
But even if you were to find the ideal prop the gain is very little a
mile or two per hour. 5500 rpm sounds about right but your running a 11 pitch prop if you can get 5500rpm from a 12 or a thirteen pitch smaller diam. would be better I would guess. but check the past posts and see what others are getting and what props they are useing on the big foot engines. your never going to get 22mph from the setup you have.
sorry. There just isnt any substitute for hp.
Frank is right about experimenting with diff props and such but being where you are it doesnt sound like you will have a lot of choices.
But even if you were to find the ideal prop the gain is very little a
mile or two per hour. 5500 rpm sounds about right but your running a 11 pitch prop if you can get 5500rpm from a 12 or a thirteen pitch smaller diam. would be better I would guess. but check the past posts and see what others are getting and what props they are useing on the big foot engines. your never going to get 22mph from the setup you have.
sorry. There just isnt any substitute for hp.
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Frank C
Trimming the bow down a little should improve speed & economy a little - as aya16 explained. Unfortunately, a hydrofoil defeats the purpose. It contributes so much drag that it actually reduces top speed. This has been tested and reported here by several owners over recent years.
Search on [hydrofoil dolefin] and click "All terms" to see earlier reports.
You might also try a second search with spelling as [dole fin].
Search on [hydrofoil dolefin] and click "All terms" to see earlier reports.
You might also try a second search with spelling as [dole fin].
Shehzad
I agree you should get more speed, something is wrong somewhere. With the help of other owners on this board and your persistance you'll get the answer. I have a 96 26x with a 50 hp 4 stroke bigfoot, fuel injected merc. long shaft 2003. bought it new this year and installed it myself. everyone seems to agree the yamaha 50t 4stroke is the same motor. My top that I can hit is 20.5mph measured with gps,that is on a flat lake ,slight breeze at my back, light load 1 person (me @ 175 LBS) 12 gal gas.
2 batteries, maybe 50-75 pounds of tools and other accessaries a small cooler 20lbs. no ballast. Approx. 500ft above sea level. Into the breeze opposite direction is 19.5 mph. rpm 5300-5400 max. either direction. prop is a solas 14x11x3 aluminum. Arabian sea is at sea level.
if you can turn 6000 rpm that is more than enough to get speed. maybe you are overloaded, or have a bilge full of water, maybe you are cavatating. maybe your motor is not mounted right. not all 14x11x3 props have the same size ears or blades. the cavatation plate should be below the bottom of the transom 1-2" mine is 2" to avoid cavatation, cavatation is a big prblem on the sea because of ocean swells, waves and wakes of passing heavy boats, I have no wedge on my transom under motor mount just a 3/8" hdep plate to distribute load.
Tom 26x
since your motor from japan it might be different, could it be short shaft?
I agree you should get more speed, something is wrong somewhere. With the help of other owners on this board and your persistance you'll get the answer. I have a 96 26x with a 50 hp 4 stroke bigfoot, fuel injected merc. long shaft 2003. bought it new this year and installed it myself. everyone seems to agree the yamaha 50t 4stroke is the same motor. My top that I can hit is 20.5mph measured with gps,that is on a flat lake ,slight breeze at my back, light load 1 person (me @ 175 LBS) 12 gal gas.
2 batteries, maybe 50-75 pounds of tools and other accessaries a small cooler 20lbs. no ballast. Approx. 500ft above sea level. Into the breeze opposite direction is 19.5 mph. rpm 5300-5400 max. either direction. prop is a solas 14x11x3 aluminum. Arabian sea is at sea level.
if you can turn 6000 rpm that is more than enough to get speed. maybe you are overloaded, or have a bilge full of water, maybe you are cavatating. maybe your motor is not mounted right. not all 14x11x3 props have the same size ears or blades. the cavatation plate should be below the bottom of the transom 1-2" mine is 2" to avoid cavatation, cavatation is a big prblem on the sea because of ocean swells, waves and wakes of passing heavy boats, I have no wedge on my transom under motor mount just a 3/8" hdep plate to distribute load.
Tom 26x
since your motor from japan it might be different, could it be short shaft?
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shehzad
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Thank you very much for your kind advises.
I would check the shaft length of the engine.
There is another point which I did not mention is that in summers, our sea gets very rough due to monsoon winds and this persist untill the middle of October. Now the sea has calm down.
Next sunday, I shall try again for full throtle and would see what happens.
I would check the shaft length of the engine.
There is another point which I did not mention is that in summers, our sea gets very rough due to monsoon winds and this persist untill the middle of October. Now the sea has calm down.
Next sunday, I shall try again for full throtle and would see what happens.
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aya16
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Shehzad points to check when you get out. make sure your engine is all the way down, ballast tank is not full. dagger board is all the way up.
look out for those young kids we have out there with big guns not sure they have seen a sailboat move so fast before. We had a coast guard
patrol here board one of our boats because they never saw a sail boat move so fast. Right Scott?
look out for those young kids we have out there with big guns not sure they have seen a sailboat move so fast before. We had a coast guard
patrol here board one of our boats because they never saw a sail boat move so fast. Right Scott?
sea conditions
Please also post sea conditions when you post top boat speed. The 20mph+ speeds using a 50hp outboard are water as smooth as glass. Wind will effect your top speed a mph or two, waves can lower your top speed 5mph or more. Also, if you are powering up swells and then down swells there might be several mph difference in the up compared to down.