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1966 18602C 18hp strange noise..help!

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berninga87

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Hello all, so I bought my first boat recently, an old 14ft sears flat bottom that came with the '66 18hp Evinrude. After some research I've come to believe this motor is probably a little overkill for the boat, and I was maybe a little naive when buying, but it's what I have to work with for now. Luckily I know two-stroke motors well enough and this one runs great and starts first pull most times, however my knowledge stops at the powerhead...The issue I'm having is in forward gear. When I shift into forward it starts to whine and gets louder and louder with more RPMs, to the point that I can hardly even hear the motor past half throttle. The prop is in OK shape..not new by any means and a little dinged but no big chunks missing. I replaced the lower unit gear oil(old oil was a little milky, but couldn't see any major amount of metal shavings.) I toyed around with it on the water for a while and the noise never changed, although sometimes I could hit the throttle and the boat would jump right up on a plane and go, others times it felt almost like the prop was cavitating and the motor would rev up but didn't pick up any speed. The noise still kept up, and got really annoying, I can't say for sure but it sounded like the noise was coming from somewhere in the upper part of the drivetrain, not something in the water, but it was hard to tell. I have tools and can do most repairs myself, I just dont know what could be causing it, help!
 
Excessive gear whine can be caused by worn gears and bushings in the lower unit. It can also be caused by something holding the drive shaft down, which jams the gears together. What can hold the drive shaft down? Rust in the crankshaft splines. Wrong size o-ring at the top end of the drive shaft. Or a big glob of heavy grease in the splines.
 
Thanks for the info! So where would be a good place to start with diagnosing my specific problem? If I take the lower unit off do you think Id be able to see anything obvious if those were the issues?
 
Take the lower unit apart and inspect gears / bushings.------If this motor was ever submerged and not recovered properly there could also be an issue with the roller bearings / crankshaft internally in the powerhead.
 
Thanks racer, I haven't gotten it apart yet but I was just looking it over today and noticed something. I'm not too savvy on outboard lingo yet but I'll explain it the best I can. So there is a little rubber "cone" on the end of the prop with a cotter pin through it. If I grab that and move it, it has quite a bit of play from side to side and endplay forward and back, moves a little bit up and down. It sounds like something is moving on the inside with it when I wiggle it, but it seems to be moving as one unit, just not held in place very solidly. Does this sound like something that could be a major issue/causing my noise issue, or is that sort of play normal? Thanks, Adam
 
Hate to be the bearer of bad news, but that lower unit is totaled. With that kind of slop in the prop shaft, you can bet the pinion shaft is worn, and it cannot be replaced without replacing the whole gearcase casting. Besides, the gears are running out of alignment, which destroys them. All together, this is the reason for your whine. Frankly, it is a wonder it brought you back to the dock. Better start looking for a good or rebuilt complete lower unit. Or cut your losses and sell the top part for parts.
 
thanks gator, I was afraid of that. I'm working with the guy who sold it to me (a week ago) as a "complete good running outboard" and hoepfully he will stand behind his word since it made this noise the first time I ever fired it up. I want to save the powerhead though, that '66 Evinrude runs like the day it was sold!
 
These motors are excellent as they were basically the same from 57 to about 76.-----Many were sold and used parts are plentiful.------------That lower unit should fit.
 
Thanks for the help guys. I talked the guy who sold it all to me into buying the motor back on the basis that he promised a "ready to fish" boat/motor/trailer. It was too big for that little Sears boat anyway. I'm going to look at a 9.8 mercury today which will be a better fit. I'm taking a tool kit with me this time to check a few things and hopefully not make the same mistake again!
 
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