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justinman

Prop Question

52 posts in this topic

Maybe some of you guys can help me? I'm pretty new and nieve to owning and maintaining a boat. I bought a 15'6 fishing boat with a 30HP mariner a couple years. By myself I can get to around 16 mph according to my GPS and plane the boat out. If I add the wife and kids top speed drops 4-5 mph and I will not plane. My prop is pretty beat up. There is about a 1/2 dime size notch out of one of the blades and all three blades have nicks and have started to turn over a bit. I'm assuming I need a new one. I'm trying to understand the science behind a prop. How do notches, nicks and turned over blades inhibit the performance? What can I expect a new prop will do in regard to speed and planing expecially with added weight in the boat. Can I expect and extra 1-2 mph or 3-4 mpg? Again sorry for sounding so nieve, I'm new to boat ownership.

Thanks, Justin

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I have a 14' jon boat with 25H Merc. 2 people in the boat I'm fine, but 3 is a way different story. I can still get on plane though, but I just got a new prop. Mine was chewed before and we still got on plane w/3, but needed to shift weight around.

I would assume you would be able to get on plane and get that extra 1-2MPH. I don't know about adding 3-4 MPG though, but maybe. My top speed is around 22, but I added a floor, front and rear casting decks, 3 batteries, mongo t-motor, etc... so it has some weight already even if it's just me.

But yes get a new prop or have yours rebuilt. 80 for a new one for me. Your's should be a around the same. Don's Used Outboard has treated me well in Maple Grove and other FM'er too.

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I would have yours rebuilt (since it's cheaper than buying a new one) and see how your performance is now that it's fixed.

Do you know what pitch prop you have now? Look for a number that has a P after it, or the number after the X, like this: 10 X 13 means you have a 13 pitch prop

marine_man

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Marine, How do you know what the proper pitch should be for my rig? Is there a way to calculate that?

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I have a 25 Johnson on a 14' Alumacraft. The beat up OMC 10x13 prop will go around 25-26 with just me. Add 300 pounds of fishing buddy and gear and it drops to around 20-21. Add a 2nd guy and I'm lucky to get 18 and it does take some time to get on plane.

I have an after market 10x13 prop that is in perfect shape. It is slower than my beat up, OMC 'river prop'. I did have to return 2 other aftermarket props because they were not true. I could feel the vibrations in the tiller.

My .02 is to buy a new factory prop and keep the old one for spare. You never know when a moron will back into your motor in the local fast food restaurant parking lot on the way to the lake.

Check the local Mariner dealer and they will be able to tell you what dimension/pitch prop you should go with, based on the size/weight of your boat.

TC

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call any type of shop that sells props, and tell them what kind of motor you have, as well as what your boat is and what your weight/how many people you go out with, they will tell you if you have the right prop

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Or you can post your information up on here and let some of the others help out...

If you're going to go new, I'd definitely check with Jay at Soderbloom's... quite a few people here on FM have been very satisfied with his prices and service.

marine_man

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Jay Soderbloom will rebuild and balance your prop, good as new, for about 1/2 the cost of a new one. He's an FM sponsor and he's very good at what he does. Give him a call. Phred52

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Soderblooms do a great job, have great customer service also. I have all my props I damage rebuilt there and have always been very satisfied.

Jay has also helped me with a few different prop questions and is willing to take the time needed to talk with you.

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Tell him Fishing Minnesota sent you. They are a great sponsor.

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Thanks for the info guys. I need my prop repaired. I will contact them ans tell them FM sent me....

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DSCN7374.jpg

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Here are a few pictures of my ride and of the prop. Does anyone have a guess on how much this weighs? I typically fish with my father in law and the 2 of us are probably 500 lbs combined. I have one battery in the back and one in the front. I have electric anchors front and back. bow mont trolling motor. 30HP w/ 6 gallon tank. It has a full floor with a live well. Steering counsel and raised platform front and back. The prop reads 9 7/8 x 11 1/4 F. What do you think in regards to my first post? Do I need more pitch to plane out my boat? I guess what I'm looking to do is get top end speed and to eventually plane out the boat with added weight. Out of the hole power would seem to be secondary. Any thoughts?

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That prop isn't pretty but doesn't look like it would slow you down too much.

How does the motor 'feel' when you're at full throttle? If it feels like you should upshift, you could probably use more pitch. If it feels bogged down, less pitch is the answer. Be careful, too much pitch will slow your boat down.

Have you experimented with the trim to help get on plane? Did that motor come off a pontoon?

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Based on your prop size (9 7/8 X 11 1/4) I'd say you're in the ballpark...

What is the holeshot like when you're running like you would normally be loaded? Adequate? Does it take a bit to get on plane, or does it pop right out of the hole?

marine_man

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That prop isn't pretty but doesn't look like it would slow you down too much.

How does the motor 'feel' when you're at full throttle? If it feels like you should upshift, you could probably use more pitch. If it feels bogged down, less pitch is the answer. Be careful, too much pitch will slow your boat down.

Have you experimented with the trim to help get on plane? Did that motor come off a pontoon? [/quote

I was out this morning. My top end speed was 13 mph. I was by myself. At full throttle it only feels bogged down when I add another person. With that added weight she wont plane. I've monkeyed with the trim & stil cant get it to plane. I bought the boat with that motor. Not sure if it came from a pontoon. Why do you ask? Maybe it just as simple as the HP is not enough for that boat????

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Based on your prop size (9 7/8 X 11 1/4) I'd say you're in the ballpark...

What is the holeshot like when you're running like you would normally be loaded? Adequate? Does it take a bit to get on plane, or does it pop right out of the hole?

marine_man

The hole shot is horrible.

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The problem I have here is there is alot of material missing from the prop and it's hard to say if repairing it will have any a substantial affect on your hole shot. Based on the damage, my first inclination is to say it wont, but will affect the top end performance. Less material, less bite. but.... is the hole shot horrible because of no bite, or...is it because it's over pitched? Does it sound boggy or does it sound likes its reving but just wont get up and go?

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The problem I have here is there is alot of material missing from the prop and it's hard to say if repairing it will have any a substantial affect on your hole shot. Based on the damage, my first inclination is to say it wont, but will affect the top end performance. Less material, less bite. but.... is the hole shot horrible because of no bite, or...is it because it's over pitched? Does it sound boggy or does it sound likes its reving but just wont get up and go?

It doesn't sound boggy, its definately rev'd up. It just wont go when loaded. Like I said, by myself I gan get up on plane and top out at around 13 mph. Do you think with more bite and leaving the pitch alone I should be able to get up on plane with a loaded boat? I'd rather have more top end speed than a better hole shot.

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If the motor revs the same loaded and empty, you could go with a steeper pitch prop. A 15' boat with a 30 horse should do much better than 16 loaded. I'm not sure about the Mariner gearing so I better not recommend any particular pitch. The prop shop of your choice can tell you.

A motor set up for a pontoon will give you absolutely no speed. The same motor could have a 11 degree pitch for a pontoon, 13 degrees for a glass boat and 15 degrees for aluminum. I asked becuase that prop doesn't look bad enough to rob you of 10 MPH. Wrong prop, or something else.

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Here's what I'd do...

Fix the prop you have (since you already own it). When you get it back take it for a spin and see what you think.

marine_man

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Well, I got the new prop today, same size. My prop guy recommended I use the same as well. It didn't make one bit of difference in hole shot or speed. I'm a little bummed frown. Don't know how much I want to sink into this especially for 2 mph. If I can get another 8-10 mph some how it my be worth it. The shop I'm talking to said if I add the fins to my motor I should be able to get on plane with a loaded boat but will lose some speed. I don't think I can sacrifice anymore speed to save on a little fuel economy. Anyone have any other ideas on why the performance is so crappy? By the way, thanks to everyone who has posted so far.

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I think you need more pitch. For example I have an 86 johnson 40 on my 16' boat with a 11 3/4 x 17 prop. By myself I cruise in the 31-32 range. I think you will notice a huge difference by bumping up to a 15 degree pitch.

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Exchange the new prop for one with more pitch and try it. Your prop guy should take it back.

Maybe something else is wrong. In the garage, take the cover off the motor, motor off, move the throttle wide open, and look at the butterflies in the carb. They should be wide open. If not, the linkage could be in need of adjustment.

Something doesn't seem right...

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