do I have a bad prop?

[7173george]

I have a 14 foot jon boat with a 19 inch transom.the motor is a 1975 evinrude that measures 18 inches from the top of the mounting bracket down to the cavitation plate.i think this should be long enough.the motor idles and runs fine.when i put the boat in the water it starts to move along as i give it more throttle it doesn't pick up more speed.it sounds like it is slipping but every now and then it will get on plane a cruise. any way to test the prop with out going back to the lake?

 

[nwcove]

Re: do I have a bad prop?

sounds like you have a spun prop hub. you can check it by removing the prop, putting a mark on the rubber hub and a corresponding mark on the prop. i dont think you can do this in a barrel. only other option would be to borrow a prop from a buddy and see if it is the prop , or the motor is just too high.

 

[7173george]

Re: do I have a bad prop?

do u think the 1 inch difference would cause this?

 

[nwcove]

Re: do I have a bad prop?

lots of guys raise their motors up so the anti cav plate is 1 inch above the keel, but depending on your particular set up , it is a possibility. but in my experience cavitation tends to be a bit a bit of a rougher feeling than a spun hub

 

[7173george]

Re: do I have a bad prop?

if the motor is too short what is the easiest way to correct it? I have a 15 hp evinrude short shaft and that measures 18 inches too.i thought this 25 was a long shaft.turns out i think it is a short shaft.

 

[nwcove]

Re: do I have a bad prop?

jmo, but the easiest way to correct a transom thats to tall, is to cut it down. id still be focusing on the spun hub. can you borrow a prop.....or borrow another 18" motor to see if the problem persists? pics of the motor on the boat would be a big help for other members to help !

 

[7173george]

Re: do I have a bad prop?

I'll take it back to the lake in the morning and do the test with the marks on the prop if it's not spun maybe i will buy a long shaft lower unit.anybody change from a short to a long shaft? wondering how hard it would be to do it.

 

[boobie]

Re: do I have a bad prop?

From your measurements it sounds like you need a long shaft mtr. Did you buy the rig this way ??

 

[7173george]

Re: do I have a bad prop?

i didn't buy it this way.i just picked up the boat.had the motor,now i need to find a long shaft lower unit.anyone know what years are interchangeable.

 

[boobie]

Re: do I have a bad prop?

If you scout around you should be able to find an extension kit for it.

 

[wilde1j]

Re: do I have a bad prop?

I would be inclined to test the prop first, before converting to a LS motor. If it's not slipping, then increase leg length.

SPUN HUB: Mark the inner and outer prop hubs with an indelible marker, run the engine in the water, under load and examine marks. If they've moved relative to each other, hub is spun. Take prop to a prop shop to have it rehubbed.

See graphic.

 

[7173george]

Re: do I have a bad prop?

thanks,The motor is to short.i ordered the part to convert it to a long shaft.I might have to wait till spring to give it test run.colder temps.are going to be back this weekend,lake might freeze up.

 

[wilde1j]

Re: do I have a bad prop?

You need more than one part ... i.e. new driveshaft, shift shaft, water tube, etc. ... not just the spacer.

 

[7173george]

Re: do I have a bad prop?

I ordered all the parts, longer shift rod,water tube ,leg ext,drive shaft,and an impeller.hopefully everything will go together without any problems.any tricks or thing i should now or watch out for?

 

[kfa4303]

Re: do I have a bad prop?

Hi george. The conversion is actually a pretty easy job. The hardest part will probably be opening the gear case so you can install the new shift rod and drive shaft, but even that is pretty straight forward. Everything goes together in the same way, they're just a bit longer is all. Be sure you hold on to all the old, short-shaft bits in case you ever want/need to convert it back to a shorty. Keep us posted. We love pics


http://www.duckworksmagazine.com/05/columns/max/4/index.cfm

 

[7173george]

Re: do I have a bad prop?

i wish i knew how to post pic. it would make things alot easier.A pic is worth a thousand words.

 

[kfa4303]

Re: do I have a bad prop?

Hi George. If you use the "Go Advanced" button in the bottom right corner of the post box, you can then add pics like you would in an email. You'll see the little paper clip icon along the top toolbar. You first upload it to an iboats folder, then insert it into the post. It's pretty simple. Give it a try and holler if you get stuck.

 

[hotshot123]

Re: do I have a bad prop?

my old bass tracker has about those same measurments and it planes fine. i think you are still going to have problems.

 

[nwcove]

Re: do I have a bad prop?

....would like to know how it was confirmed that the boat requires a long shaft? did you check the prop?.....did you try a different 18" motor.....or try your motor on a shorter transom boat? just hoping you didnt go out and spend your money on parts you didnt need.

 

[7173george]

Re: do I have a bad prop?

i went back to the lake with the prop marked.the prop isn't slipping.when i'm at the dock with the motor idling the motor is quiet.when i start to accelerate it gets really loud. seems like the exaust is up out of the water and the prop is in the white water where it's not pushing the boat.I hope you guys understand what I'm trying to say, not sure i am wording it right. It seems like the motor is to high and not pushing in good water.