25 johnson drive shaft

[jessieb]

Hi i need some help with a 1975 25 johnson, its keeps braking the drive shaft i have change 2 all ready and don't want to brake another one some one please help the gears are fine had them checked by a machine shop, what could be doing this? when i say the drive shaft i mean the shaft thats gose from the power head to the lower unit they sell for about 300.00 a pice i can't buy one ever trip out PLEASE help.

 

[Steve135]

Re: 25 johnson drive shaft

Hey jessieb- I have never heard of that happening? I regualy cut drive shafts from long to make short ones and have never had one break even after they are welded. Wow 300.00 bucks I should raise my price. What breaks the splines or the shaft in half? Is it twisted? 25 hp dosen't seem to have enought to break that size shaft.<br />steve

 

[jessieb]

Re: 25 johnson drive shaft

ok stinky2 first its breaks at the splines broke one at the top and one at the bottom, and how much do you charge to make one?

 

[Steve135]

Re: 25 johnson drive shaft

jessieb - If they are breaking when they are solid they will surely breake after being welded. I just can't see spending 300.00 bucks for a drive shaft. I get the ones I need from a boat junk yard! It depends on the day for the price so I can't quote on the price. Is it short or long shaft? I might have a long shaft laying around.<br />steve

 

[jessieb]

Re: 25 johnson drive shaft

its a short shaft and its breaks at the splines 1 at the top 1 at the bottom a friend told me that my housing may be bent putting the shaft in a bind but when i install the shaft i can spin it very easy (with out water pump)after the water pump is intalled i can spin it with some plyers with not much force just use plyers to get a grip on it.

 

[Steve135]

Re: 25 johnson drive shaft

jessieb I am at a loss to why it breaks. I will check the shop out later today and see if I have a short shaft for the 25 hp johnson out there. <br />steve

 

[jessieb]

Re: 25 johnson drive shaft

ok thanks for your help let me know if you have one and how much you want to get for it <br /><br />P.s. please don't forget to add shipping to you price.

 

[G DANE]

Re: 25 johnson drive shaft

Hi Jessie B<br /><br />If something was bent, i think the shaft would break at the same end every time.<br /><br />Can you have anything floating around in your lower unit gear, a tooth from a former broken gear or something, when it locks up, the shaft will break. Disassembling this type of lower unit isnt hard. How does the lower unit oil look like.<br /><br />You can also check if the power head is correctly bolted on the leg- but i never saw one that wasnt.

 

[jessieb]

Re: 25 johnson drive shaft

thanks G Dane<br /><br />the gears are brand new, the oil is fine, no trash floating around to jam up gears, i have broke 2 shaft 1 brok at the top spline,1 broke at the bottom spline Could the housing be bent causing this to happen?

 

[G DANE]

Re: 25 johnson drive shaft

Hi Again Jessieb<br /><br />Something is completely wrong here. Did you hit anything ? This shaft is so flesible, it will take 1/2 turn alone if the propeller hits anything, to save the gears and cranck.<br /><br />Have you had the lower gearcase apart as you know it is clean inside. A screw or a lost roller wouldnt pollute the oil, but lock up gears if it gets stuck. Is your powerhead prober bolted to the leg ? I dont think housing can bend that much without breaking, the splines can take up some of a tolerance as they have some play at top in cranck.

 

[ob]

Re: 25 johnson drive shaft

Jessie b , before you waist money and time to install another driveshaft there is apparent mechanical problem between crankshaft and lower unit.Sounds like mechanical looseness either in spline backlash or take off adapter from engine crank having a hammering effect and breaking driveshaft .This is assuming you have possitively ruled out binding in lower unit.

 

[RPJS]

Re: 25 johnson drive shaft

If as you say the shaft spins OK when fitted to the lower unit it would sugest that the problem is related to the power head mounting. If when bolting up the lower unit to the motor it pulls slightly out of square with the shaft the resulting bending force when the motor is running would result in the shaft failling. A 25hp motor would not have the power to sheer a drive shaft if the lower unit siezed. Check that the shaft fits into the crank shaft correctly and that you can push the lower unit fully into place without forcing the drive shaft. If the power head has been removed recently you should also ensure that it has been bolted down correctly and is sitting flat on the top of the leg. There are no universal joints on these shafts to correct any alignment problems.<br /><br />Good Luck<br /><br />Richard

 

[jessieb]

Re: 25 johnson drive shaft

Thanks to RPJS,OB,G Dane for all the replys<br />but let me give you a little more info on this motor <br /><br />1. the motor sat up for two years<br />2. i bought it<br />3. i rebuilt the lower unit complete<br />4. gears were crack where the brass goes<br />5. changed the gears Brand New Gears<br />6. had lower unit sand blasted inside and out<br />7. installed new seals,gears,gaskets,and lube<br />8. went fishing!<br />9. drive shaft broke at top spline.<br />10.installed new shaft after having gears blacklighted for cracks<br />11.went fishing (brand new Drive shaft)($300.00)<br />12.shaft broke again at bottom spline.<br />13.here i am NEED HELP<br /><br />i will check the power head fore alinement and let you know the out come thanks again.<br /><br />P.S. I did not hit anything first time or second time i was in open water both times.