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Need Prop Help!

Brandon I have a 35hp Johnson(not sure what year model, probably early '80's.) The prop has 10x13 stamped on it. When I look for a new prop do I have to get one with the same stamp, or can I use another size? If so what is recommended? Also what do the numbers stand for? Thanks in advance for any help.

-Brandon

2002-03-02
boatsnmate 1 The numbers are the pitch you can use 10x13 10x15 10x17 the difference will be inhole shots and trolling speed. 2002-03-02
dharrin1 Hello Brandon.
The question cannot be answered without knowing the size of your boat and the load you put on your engine as far as weight in the boat is concerned.Go to www.miwheel.com and their website will ask you a series of questions.In the end you will know what size is good for your situation.
stay afloat!!!
2002-03-02
dharrin1 It's me again.
The first of the two numbers you mentioned ,is the diameter of your prop,the second is the "pitch" .Imagine your prop cutting through jello in one rotation it will move 13 inches forward through the jello.It has to do with the angle of your blades.The lighter and smaller your boat,the bigger the pitch you want.The bigger and heavier the less pitch.
rolmops.
2002-03-02
Brandon I tried the website, but I don't have all the answers for the questions so therefore I can't get an answer. Let me try and give you some ideas of what I have and maybe I can get a recommendation.

1982 35hp Johnson
14ft 48"wide aluminum boat
Gross weight w/passengers is approx. 900-1000
16" transom

-Brandon
modified-V Hull

2002-03-06
MGuckin Just a thought. If you have a tach and you are revving too high, (suggested rpm range should be stamped on the motor somewhere) every inch of pitch increase would lower your rpm by 200. Diameter would remain the same +/- depending on manufacturer.
I ran a 10x13 on a 35 hp, 14' fiberglass bass boat. You are about 400 lbs lighter load.

Mike
2002-03-07
Brandon I can't find any info about the RPM's on the motor and I don't have a tach either.

Mike,
If you ran the same size motor w/400# more weight does that mean I should go up a little on pitch? And if so how much?

What would be the main difference if I changed from a 10x13 to a 10x15 or 10x17? Would the boat go faster? Would that put more of a load on my motor? Sorry for all the questions, but I need to learn somehow.

-Brandon

2002-03-07
almost retired again Hi Brandon,
Usually the higher the pitch the faster you go; however it's like Mc Gluclen said,you should use a tach. your engine is designed to run at a specific RPM at wide open throttle. If it's running too fast it can damage the engine , and if it's running too slow because of the prop it will cause the engine to lug,or strain therefor damaging the engine. I would borrow or buy a good tach to determine this. I don't know what the recommended RPM's of your engine are,but if yiu can wait until tomorrow I'll look it up and let you know.
2002-03-07
MGuckin Possibly a 15"......but as almost retired again says get a tach. No where near as expensive as a new motor. I will guess that manufacturer rec. is from 4500-5500 rpm but not sure. Look on the port side of the motor mounting bracket. It should be stamped there.
2002-03-07
Brandon Thanks for all the replys. I'll look again tomorrow to see if I can find the recommended RPM's. The guy at the boat shop today told me he thought it would be right around 5200. If that's the case which prop should I go with? How hard is it to install a tach? I'm going to look into one tomorrow as well. Thanks again for all the helpful info.

-Brandon

2002-03-07
Brandon Well I found the Tach info. It is 5200-5800.

-Brandon

2002-03-08
almost retired again Hello again Brandon,
Well as promised I have the specs, but someone else has already answered you. Anyway the service manual says it's rated to run between 5200 & 5800 the max HP is developed at 5500 RPMs. If you have an induction tach. connect the pick up around any spark plug, wire or coil primary wire start your engine and read the RPMs. The manual recommends a good prop to start with on your boat is a 13X15.
Hope this helps
2002-03-08
MGuckin Okay, now that you found that out, buy or borrow a handheld tach if you don't want to install one. Post your full throttle rpm, under load (in the water underway) just dont let it go over the max stated. To be honest your boat sounds a little overpowered. Dang thing should fly once it is set up.

Mike
2002-03-08
Brandon I thought that since I had a 10 x 13 now that I had to stay with the 10 x ?. Almost Retired said that it recommended a 13x15, would this stilll fit my motor? I'm trying to locate a tach to borrow for now, then I can go from there.

-Brandon

2002-03-08
almost retired again HEY bRANDON
Sorry about the typo,I don't think a 13X15 would fit. Ment to say a
10X15
Sorry I can only type with 2 fingers
2002-03-08
Brandon I didn't think so, but I wanted to make sure. Thanks again for all the help.

-Brandon

2002-03-09

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