motor to small?? or wrong angle

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motor to small?? or wrong angle

Postby jkreg » Mon Sep 23, 2013 3:29 pm

I took my boat out for the first time with the blind on it today and I know that the extra wieght will slow my 15HP motor down but just before it would plain?plane? the engine would rev up as if the prop wasn't in the water anymore I dont want to blow my engine but I would really like to get up to speed......do I need to adjust the angle of the prop.....raise or lower the engine.....move wieght to the front or rear??? any help is much appreciated
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Re: motor to small?? or wrong angle

Postby Boatman » Mon Sep 23, 2013 4:34 pm

Try it down 1 notch, the tilt pin that is.
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Re: motor to small?? or wrong angle

Postby threedogs » Mon Sep 23, 2013 7:23 pm

Put the pin in the in the notch closest to the boat and try that. Keep going up a notch till it slip again and back it down one notch. It should be fine there.
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Re: motor to small?? or wrong angle

Postby T Man » Mon Sep 23, 2013 8:07 pm

Spun hub.

Take a sharpie and draw a line through on the hub ofthe motor. Run your motor in the water and then look and see if the lines still line up.

Image
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Re: motor to small?? or wrong angle

Postby Elvis Kiwi » Tue Sep 24, 2013 2:08 am

theres a name for that but cant think of it at the moment, motor pulls in air and puts prop in empty space.sort of like when you pull bath plug and whirlpool gets big enough and sucks air too. I do get it from time to time hooning around...cavitation :thumbsup: plurry brain in slow mode but got it in the end. deeper would be better and tilted further forward should help too. tootoo with the tilt till you find what goes quickest, I know there is a big difference between a empty boat and one loaded up to the gunnels in where motor works best. Ive only got a 6hp on my 13" fryan tinnie so any adjustment is noticeable.
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Re: motor to small?? or wrong angle

Postby feet down nebraska » Tue Sep 24, 2013 3:22 am

T Man wrote:Spun hub.

Take a sharpie and draw a line through on the hub ofthe motor. Run your motor in the water and then look and see if the lines still line up.

Image



Was going to say the same thing happened to me.on my 15 barely made it home
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Re: motor to small?? or wrong angle

Postby T Man » Tue Sep 24, 2013 8:53 am

Elvis Kiwi wrote:theres a name for that but cant think of it at the moment, motor pulls in air and puts prop in empty space.sort of like when you pull bath plug and whirlpool gets big enough and sucks air too. I do get it from time to time hooning around...cavitation :thumbsup: plurry brain in slow mode but got it in the end. deeper would be better and tilted further forward should help too. tootoo with the tilt till you find what goes quickest, I know there is a big difference between a empty boat and one loaded up to the gunnels in where motor works best. Ive only got a 6hp on my 13" fryan tinnie so any adjustment is noticeable.


Close, cavitation happens when the water literally boils off the surface of the propeller because the pressure is so low. You are thinking of ventilation.
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Re: motor to small?? or wrong angle

Postby jkreg » Tue Sep 24, 2013 6:00 pm

ok so I tried down a notch...which really sucked.....and up a notch....not any better ....although when I put it back to the regular position it did run better....I ALMOST got to full plane but thats all I got.....it didnt spin out for a little while but after it hit a few waves and bounced just right it started to.....So I backed off throtle ever so litle to stop the high rev without losing thrust and put back up she runs ok just think the blind might be a smidge heavy.....Also I am not running in the deepest of waters things are kinda dry around here right now


On a positive note I shot 2on Saturday, 4 yesterday and 3 today.... last day of first season tomorow going for broke baby.....then Ill check the hub lol
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Re: motor to small?? or wrong angle

Postby threedogs » Tue Sep 24, 2013 6:24 pm

jkreg wrote:ok so I tried down a notch...which really sucked.....and up a notch....not any better ....although when I put it back to the regular position it did run better....I ALMOST got to full plane but thats all I got.....it didnt spin out for a little while but after it hit a few waves and bounced just right it started to.....So I backed off throtle ever so litle to stop the high rev without losing thrust and put back up she runs ok just think the blind might be a smidge heavy.....Also I am not running in the deepest of waters things are kinda dry around here right now


On a positive note I shot 2on Saturday, 4 yesterday and 3 today.... last day of first season tomorow going for broke baby.....then Ill check the hub lol



Then you most likely have a spun prop. Try what T man told you in his last post.
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Re: motor to small?? or wrong angle

Postby omaha » Tue Sep 24, 2013 6:44 pm

.
Last edited by omaha on Tue Sep 24, 2013 6:45 pm, edited 1 time in total.
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Re: motor to small?? or wrong angle

Postby omaha » Tue Sep 24, 2013 6:45 pm

Is the shaft size right for the transom? But yeah sounds like a spun hub
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Re: motor to small?? or wrong angle

Postby threedogs » Tue Sep 24, 2013 7:11 pm

omaha wrote:Is the shaft size right for the transom? But yeah sounds like a spun hub



Good catch...
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Re: motor to small?? or wrong angle

Postby gearhead80 » Tue Sep 24, 2013 8:52 pm

What brand and year outboard is in question here? Sounds like a hub that has slipped. But what if It doesn't have the rubber style hub assembly that could slip?
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Re: motor to small?? or wrong angle

Postby t_baker » Tue Sep 24, 2013 9:03 pm

gearhead80 wrote:What brand and year outboard is in question here? Sounds like a hub that has slipped. But what if It doesn't have the rubber style hub assembly that could slip?



Shear pin
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Re: motor to small?? or wrong angle

Postby T Man » Tue Sep 24, 2013 10:31 pm

t_baker wrote:
gearhead80 wrote:What brand and year outboard is in question here? Sounds like a hub that has slipped. But what if It doesn't have the rubber style hub assembly that could slip?



Shear pin


Yup, although typically shear pin failures show themselves at lower rpm.
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Re: motor to small?? or wrong angle

Postby Shell Shocked » Wed Sep 25, 2013 6:48 am

Here's my 2 cents!

The transom height is incorrect for the boat. My theory is the added weight displaces more water so what was not a problem under a light boat is now noticeable with a weighted boat.

Just a thought!
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Re: motor to small?? or wrong angle

Postby threedogs » Wed Sep 25, 2013 8:22 am

We need a pic of the offending motor and boat!
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Re: motor to small?? or wrong angle

Postby T Man » Wed Sep 25, 2013 12:21 pm

Shell Shocked wrote:Here's my 2 cents!

The transom height is incorrect for the boat. My theory is the added weight displaces more water so what was not a problem under a light boat is now noticeable with a weighted boat.

Just a thought!


Probably not. Added weight would cause the boat to sit lower in the water. If the weight were too much for the motor, it wouldn't be able to get past a certain rpm. Since It will almost get on plane, there are 2 possibilities: broken shear pin/spun prop or blowout. Since the motor seemed to run fine before the blind, I will assume, that the motor length isnt a problem. If the shaft were too short for the transom, the problem would have been evident already and the blowout would be evident, if it were too long, it would do the opposite of what it is doing and lug the motor. I would say it's probably not blowing out, but the added weight is causing a spun hub to be more noticeable. Unless the motor is incredibly under propped, the miniscule additional weight of the blind shouldn't cause blowout. The symptoms sound to me like a classic spun hub.
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Re: motor to small?? or wrong angle

Postby Elvis Kiwi » Wed Sep 25, 2013 11:50 pm

maybe the blind adds weight forward???? causing motor to be higher in water???
pictures are always good.
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Re: motor to small?? or wrong angle

Postby T Man » Thu Sep 26, 2013 12:10 am

Elvis Kiwi wrote:maybe the blind adds weight forward???? causing motor to be higher in water???
pictures are always good.


Maybe, but I prefer to stick to the KISS principle until you run out of easy solutions.
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Re: motor to small?? or wrong angle

Postby omaha » Thu Sep 26, 2013 6:50 pm

T Man wrote:
Shell Shocked wrote:Here's my 2 cents!

The transom height is incorrect for the boat. My theory is the added weight displaces more water so what was not a problem under a light boat is now noticeable with a weighted boat.

Just a thought!


Probably not. Added weight would cause the boat to sit lower in the water. If the weight were too much for the motor, it wouldn't be able to get past a certain rpm. Since It will almost get on plane, there are 2 possibilities: broken shear pin/spun prop or blowout. Since the motor seemed to run fine before the blind, I will assume, that the motor length isnt a problem. If the shaft were too short for the transom, the problem would have been evident already and the blowout would be evident, if it were too long, it would do the opposite of what it is doing and lug the motor. I would say it's probably not blowing out, but the added weight is causing a spun hub to be more noticeable. Unless the motor is incredibly under propped, the miniscule additional weight of the blind shouldn't cause blowout. The symptoms sound to me like a classic spun hub.


Your partially right, if the boat is sitting lower and the motor is too short the motor when at speed is now hitting a larger air pocket. You can move a motor up but for ever inch up you need to have 2 of set back so that the motor is still in water and the prop is not cavitation in the air bubble. Btw a motor can destroy its lower unit if ran in a cavitation bubble long or hard enough. It may be a spun hub, but I am gonna say wrong size motor. And before when the boat was lighter it wasn't an issue cause the air bubble was smaller since the boat was riding higher n the water so the air behind the boat was was less cause the boat was displacing less water.
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Re: motor to small?? or wrong angle

Postby omaha » Thu Sep 26, 2013 6:55 pm

It's the same effect if you go around a hard corner too fast in your boat
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Re: motor to small?? or wrong angle

Postby Elvis Kiwi » Fri Sep 27, 2013 1:41 am

we mount our 6hp merc just off centre on our fryan...it puts it in cleaner water as its just off the deep v that way. it also helps counteract my fat butt :no:
If Im hooning in flat water and get her up on the plane it will cavitate...sometimes but will hardly ever do it in rough water..and man do I love getting out and playing when all the big boats have gone in cause its too rough...bunch of blouses :tongue:
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Re: motor to small?? or wrong angle

Postby jkreg » Wed Oct 02, 2013 3:52 pm

ok so I havnt figured out how to load files to get you guys the pics but I will work on that...... although while cleaning my garage I found to wings that look like they attatch to the fins above the prop.....problem??? maybe....
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Re: motor to small?? or wrong angle

Postby T Man » Wed Oct 02, 2013 4:28 pm

jkreg wrote:ok so I havnt figured out how to load files to get you guys the pics but I will work on that...... although while cleaning my garage I found to wings that look like they attatch to the fins above the prop.....problem??? maybe....


Doubtful, have you checked to see if you have a spun hub?
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