61' Big Twin 40HP runs great but no speed!!!

[griffn1]

We have a 1991 Evinrude Big Twin 40hp that runs really good but stops transfering power to the prop at about 1/4 power. If you very gently nudge the power up it will go up to a certain point and then the RPM's shoot up and it stops transfering the power to the prop. we rebuilt the foot after discovering the problem and it still does the same thing. Any help would be greatly apreciated!!

 

[Lark40]

Re: 61' Big Twin 40HP runs great but no speed!!!

If you engine is a 1961 model as your heading states, then it has a shear pin, so it that would rule out the prop slipping at certain speeds.<br /><br />The drive shaft is splined at both ends, and, if those splines look good, then it's not slipping there. That would leave the drive gears and the clutch dog. But, you say you've rebuilt them.<br /><br />What shape is the flywheel key in?<br /><br />When I eliminate the mechanical problems, I usually find the cause is cavitation caused by seaweed or incorrect transom mounting.

 

[griffn1]

Re: 61' Big Twin 40HP runs great but no speed!!!

I am not sure that we checked the upper portion of the drive shaft where it connects to the power head. My dad has been doing all of the work. I will pass this info on to him. Thanks alot!

 

[KT64TM]

Re: 61' Big Twin 40HP runs great but no speed!!!

You need to have a new hub pressed into the prop. shouldnt be nore than $20 bux at a prop shop. <br /><br />this happened to me last year. slowly increase the throttle and its fine, hammer it, and it slips.

 

[SeaMasterZ@aol.com]

Re: 61' Big Twin 40HP runs great but no speed!!!

get a spare prop on ebay in case you spin another prop, it happens

 

[griffn1]

Re: 61' Big Twin 40HP runs great but no speed!!!

Thanks alot guys! I checked the prop last night and we think that this is more than likely the problem. The first time we took it out it worked fine so we didn't think to check it. Thanks again you guys are great!

 

[griffn1]

Re: 61' Big Twin 40HP runs great but no speed!!!

This was the problem!! We feel kind of silly now but we are just glad it is working. The boat runs great! As a side note we checked with 4 local boat marinas and no one would re press a prop for us so we had to buy a new one $75.00!!! but oh well. Thanks again

 

[jstromsk]

Re: 61' Big Twin 40HP runs great but no speed!!!

For a hub rebuild, try Precision Propeller Service 414-384-3330<br />902 W Bruce <br />Milwaukee, WI

 

[griffn1]

Re: 61' Big Twin 40HP runs great but no speed!!!

Thanks! will do