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1971 Evinrude 100 w/ HydroElectric Shift - Jumping under load

Beau

New member
Hello,
Newb here on this forum. Been restoring an old new boat 1969 Winner MiniKai running a Evinrude 100Hp (100193A) Starflite w/ HydroElectric shift. I own the manuals and have read through existing threads on here to search for the issue i'm encountering. The lower unit shifts fine, however, only under load in forward (Starting to come up onto plane), it jumps/pops (sounds eerily like hitting something underwater). When I drop the revs it runs normal at low RPM. I tried bringing up the RPM in reverse to see if the problem would follow and it would not. This leaves me to suspect that either the DOG or forward gear is warn out. Any suggestions? Thanks in advance.
 
In forward gear, the dog is locked into forward gear via a spring loaded shifter dog... no hydraulic oil pressure is being applied.

That lower unit demands "Premium Blend" gearcase lube, also known as "Type C". Should you be using the mechanical shift lube of "HiVis"... that would cause a malfunction of the oil pump... in which case switch to what the unit calls for to see if that cures the problem, and if it does not, then your suspicion is correct.
 
Thank you Joe. Yeah, using the correct Type-C lube. Understand that the forward gear is locked with the spring and not engaged until oil pressure is applied. Guess I'll be pulling the lower unit, probably best to give it a once over anyway, new seals, water pump, paint job. Thanks for the reply. Cheers.
 
You might try another prop.-----Does the motor just wind up or is it banging in and out of gear ?-------Easy units to overhaul ( in my opinion ) and you might find that the bore for the shift piston is contaminated.-----Junk ( from the oil screen ) might be embedded in that bore.----Then the spring can not force the clutch dog all the way into forward !
 
You might try another prop.-----Does the motor just wind up or is it banging in and out of gear ?-------Easy units to overhaul ( in my opinion ) and you might find that the bore for the shift piston is contaminated.-----Junk ( from the oil screen ) might be embedded in that bore.----Then the spring can not force the clutch dog all the way into forward !

Racerone

Once load starts to come up with RPM it bangs in and out of gear. Pretty terrifying, I've hit a reef at WOT, not fun. Very similar sensation.
I'll inspect the shift piston bore per your suggestion as well. Thanks for the reply.
 
It is rare for a hydro-electric clutch dog to wear out, but certainly possible. If it is worn out, I go along with the thought that it isn't sliding totally into forward gear.
 
Hello. Finally got the funds together and the honey do list is down to manageable level, so I was able to start the lower unit refreshing.
After fighting with the CirClips, what a pain here I thought the bearing carrier was going to be my nemesis, I was able to get into the meat of the gearbox.
Upon inspection, there is obvious wear and tell tale sign of slippage on the dog clutch, forward and reverse gear mating surfaces. It's nice to have those "A-HA!"moments when delving into unfamiliar water having only an uneducated but informed guess of the issue. Couple of pics of the parts will follow if I can figure out how to upload. I've ordered the forward and reverse gears, thank you eBay and NOS. I purchase the dog clutch a while back when this thread was initially started. Next nut to crack is the pinion gear to pull out the FW gear and clean out the gear case. ~Tom

IMG_9193.jpg
IMG_9195.jpg
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Agreed.-----Have never seen wear like that on the forward gear and clutch dog.-----Best to find out why this happened and correct the fault.
 
Truth be told I have no honest way of knowing the hours.
I purchased the boat from the original owners son last year. It came from Oshkosh Wisconsin and spent the majority of its time on Lake Winnebago. From what I understand this boat was like a child to him, as his son put it "he liked the boat more than his children".
 
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