what's the original size prop?

[spacerust]

i have a Mercury 50 (Serial# A132112) with a 11 inch diameter 10 degree prop. I have a spun hub. I don't have a tach yet but am looking to get the original size prop and install a tach then go from there. I called one of the local marine shops to see if they have a prop for my motor. the guy told me that the propl i have is too small. that a 15-17 degree prop originally came with this motor. now i'm confused. i have a '17 bass boat with this 50hp motor and i don't know which degree to order. could anyone tell me what originally came with this motor, recommeded rpm at wot, and a reputable brand for replacement? The marine parts guy said the prop he could get was a michican prop and it sold for $159 plus freight which would bring it out to about $182 next day. thanks for your help.

 

[mpsyamaha]

Re: what's the original size prop?

the 50 seems small for a 17ft boat so the prop probably is a low pitch. however a 10 is like a pontoon boat prop, so im not sure what you need. i would guess a 13 pitch might be a good place to start.

an accurate tach and if possible a gps to get the exact wot speed will be necessary to determine an baseline to work from. as for the merc 50, i think the max wot is 5500 on the 2stk and 6000 on the 4stk, dont know which one you have. and im sure that if im wrong someone will correct me

 

[spacerust]

Re: what's the original size prop?

i have a two stroke. now i'm really getting confused. anyone have any other suggestions.

 

[Silvertip]

Re: what's the original size prop?

A 17 foot boat typically has a maximum HP rating of 75 - 90 HP and some even higher. The rule of thumb is that acceptable performance is achieved with no less than 75% of the maximum rated HP. That boat should have no less than a 70 HP motor. Next, prop pitch is measured in inches of pitch, not degrees of pitch. There is also no such thing as a standard prop for motors in the 40HP and up range. In fact they aren't even shipped from the factory with them. Why? because the factory has no idea what size boat, type of hull, boat weight, etc., the motor will be installed on. A 15 or 16 foot boat will typically have a 13P prop on a Merc motor with a 1.83:1 gear set. Your 10P is probably causing the engine to over rev. Your approach to determining what you need is also backwards. Get the tach installed first. Then make some wide open throttle runs with the 10P prop and what you consider an average load. Note the engine RPM. If the engine is running faster than 5500 - 5700 rpm you need to go to a prop with more pitch. If the engine cannot reach 5500 RPM with a 10P prop you would be advised to get a bigger motor. Simply dropping pitch more would not likely make for a very happy combination.

 

[spacerust]

Re: what's the original size prop?

thanks for the info but right now i have a spun hub so i don't know what prop to buy to start over.

 

[Silvertip]

Re: what's the original size prop?

Used props are cheap. Check e-bay and craigs list for a 12 or 13P. Even if its not right you at least get an idea where you need to be. I think you need to be in command of a bigger engine but that's just my opinion. How did the boat perform before you spun the hub.

 

[Turbo1]

Re: what's the original size prop?

What make is yer bass boat?....Guys, he may have one that's very light and may flat out fly with a 50...
What kinda boat ya got there?

 

[spacerust]

Re: what's the original size prop?

it's an 86 '17 bass tracker. dry weight is 600 lbs. it was fine before the spun hub. i was able to get on plane. the only thing i don't know was the rpm's i was running but once it spun i knew i was overreving.

 

[Silvertip]

Re: what's the original size prop?

That would have helped if we knew that a littler earlier but I should have asked. In my neck of the woods a bass boat is a fiberglass Ranger/Stratos/Triton/Warrior so shame on me for not asking. But even more important is the fact that the prop was a 10P. The dealer is right then. You should probably be in the 15 - 17P range on a boat that light. Click the Marine Store button right under the iBoats logo at the top of the page. Scroll down to Propellers. From there you can key in your Year, Make and HP and you will see a list of props for your engine.

 

[spacerust]

Re: what's the original size prop?

i appreciate all your help. now i was planning on going with an aluminum for now but there are different brands and replaceable hubs. i like the idea of a replaceable hub so i can order a spare in case i get another spun hub on the water. do you have any receommendations? i know you get what you paid so i am not worried about the cost, just want the security of peace.

 

[spacerust]

Re: what's the original size prop?

also the diameter was 11 inches. should i be looking at a different diameter as well?

 

[walleyehed]

Re: what's the original size prop?

The diameter is a feature of the design...as pitch increases, the diam. will usually decrease slightly.
I also have a 17ft Tracker..it came with a 40hp merc. 11P at 5500rpm.
I put a 70hp merc on it, and went to a 12P and it swings that about 6000.