Hello All, Need Advice on Prop Shaft Size for '69 85hp V4

[guardian452]

First off, what a great forum! Keep up the good work! <br /><br />Not too long ago, I got the urge to own a boat. Something big enough to have some fun with, but something old enough that I could afford. "Old enough" really means that I was willing to buy something cheap, even though it might need a little fixing. I don't mind fixing stuff because that's one of the best ways to learn.<br /><br />I got what I bargined for from a friends brother. An older 16ft fiberglass cutter with a deep vee hull and a 1969 85hp Johnson Hydroelectic shift motor. The boat needs a new floor and paint job, and the motor has a few issues that made themselve apparent after a few brief sea trials. For this topic, I'll only talk about one of the problems. <br /><br />But first I just gota say....What possesed anyone to design and manufacture such a shifting system! Yikes.<br /><br />Anyway, when I got the boat home, the very first thing I did was replace the water pump impeller and the oil in the lower unit. Even though the previous owner said that the motor had been properly prepared before being put into storage, I noticed that the gear oil was slightly cloudy when I drained it for the first time. I figured I'd keep an eye on that.<br /><br />I ended up changing the lower unit oil several times during those first test runs because the oil was obviously being contaminated with water.<br /><br />I know that the leakage could be from the Filler and Vent screws, but I have reasons to doubt that. <br /><br />Now that the weather is getting warmer, I can start working on the boat again, so I've started my first engine project this year by pulling the lower unit to change the seals. After removing the upper drive shaft bearing block, those seals do look a little rough, so I think I'm moving in the right direction.<br /><br />I just ordered a lower unit seal kit(Sierra), from my local dealer, but something the parts guy said to me made me think twice. I ordered the seal kit for the 1969 85hp "small prop shaft" beacause this matches the year of my motor. <br /><br />But... the previous owner told me that the entire lower unit had been replaced after an accident. I can see a set screw in the side of the lower unit near the water intake holes, that is not shown in my 1969 drawing, but is shown in my service manual (not factory) as part of a 1972 lower unit. <br /><br />The seal kit for a 1972 85hp OMC is descibed as being for a "Large Prop Shaft".<br /><br />Does this mean diameter, or something else? Could someone eloborate on this?<br /><br />I have measured the propshaft diameter on this lower unit as being exactly 1 inch. I took this measurment just outside of the prop shaft oil seal.<br /><br />Any comments would be greatly appreciated. <br /><br />Sorry for the ramble.<br />Thanks in advance.<br /><br />Sean

 

[WillyBWright]

Re: Hello All, Need Advice on Prop Shaft Size for '69 85hp V4

Welcome to iboats. <br /><br />Here is a link to an iboats page that shows pictures of the kits at the bottom. I can't answer your seal question, but maybe those pics will help. seal kits <br /><br />Johnson embarked on electric shift in the 60s. With the first version, forward and reverse gears were engaged electromagnetically. The ignition system was a magneto, completely separate from the rest of the electrical system. So it was possible to suffer an electrical problem out on the water eliminating the shifting, even tho the motor was otherwise running fine. The HydroElectric gearcase includes a failsafe. It's always in Forward until it's electrically shifted to neutral or reverse. That way, if the motor is still running and the electrical system fails, your gearcase is in Forward to get you home. <br /><br />Electric shift gearcases have a somewhat infamous reputation and they were abandoned in the early 70s. Ironically the new trend of the 21st century is toward electrically controlled throttle and shift. We'll see.....

 

[guardian452]

Re: Hello All, Need Advice on Prop Shaft Size for '69 85hp V4

Thanks for the info WillyBWright. Glad to be part of this forum now.<br /><br />I've already looked at the pictures of the seal kits listed here at iboats, but its kinda hard to tell if the prop shaft seals are different diameters.<br /><br />The worst thing that can happen is I have to buy another seal kit. Not a big deal.<br /><br />It would be nice if someone had a list of dimensions for these seals and o-rings, cross referenceing them to the OEM part numbers. That would help identify which prop shaft I have.<br /><br />As for the hydroelectic shift. So far I have two opinions on the fail safe mode of being in Forward gear with no power. <br /><br />Its good to have Forward gear if you have a solinoid/electical/hydraulic problem. But its anoying that you cannont leave the big motor in the water when using a trolling motor, because you cannot select Neutral and allow the prop to spin free.<br /><br />The first time I ran the trolling motor, I could hear the dog clutch clicking as the prop on the big motor was spinning. I quickly figured out this was due to the lower unit being in Forward gear instead of Neutral. Anyway, I don't think the dog clutch overide was built to be spun for any extended amount of time like that, so I pulled the big motor up, and steered with the tiller on the kicker. Live and learn.<br /><br />Sean

 

[ledgefinder]

Re: Hello All, Need Advice on Prop Shaft Size for '69 85hp V4

The 1969-72 V4s used the hydroelectric lower units, but as you say the later models had a larger diameter propshaft & you've simply got the later model. If you want to check, the later model propshaft is the same diameter, at the propshaft seals, as all the later model (1973+) mechanical shift units. Order parts for a 1972 85/100/125 and you'll be fine. I'd be happy - the skinny early models did occasionally bend their propshafts. With the fat, later-model propshafts, the rock bends first!