68 9.5 Horse Johnson Engine runs, boat doesn't go

[Tye2791]

I don't know much about outboard motors so this may be a stupid question. I have a 68 9.5 horse Johnson Outboard. Engine starts and runs well. However, it seems to slip out of gear (or something) the faster I try to go. I had this problem especially this weekend when going throu lots of leaves. I had to keep slowing down to idle and then could take off slowly and it would push the boat, but eventually it seemed to hit a "bump" and that is when it seemed to slip out of gear and wouldn't push the boat. Looking at the prop in the water it seemed to still be turning. I took off the prop and there was some fishing line wrapped around the inside which I removed. The pin (I guess this is what you call it) inside that allows the prop to turn is very slightly bent. Would the fishing line wrapped around the inside or the slightly bent pin cause this problem or is it something else? Thanks for the help.

 

[Chinewalker]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Could be several things. First vote is for what's called a "spun hub". Your propeller is actually three pieces. The outer portion that you see when it's on the motor. The inner portion that actually contacts the propshaft. And the rubber hub that joins the other two pieces. The rubber hub is designed to slip if the unit hits something. It can degrade over time and allow the outer part to slip as the motor runs. Easy way to check is to mark the prop nut and prop with a Sharpie marker. and not whether the marks are still aligned after running the motor.<br /><br />- Scott

 

[fireman57]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Chinewalker has it right. The only thing he forgot is Welcome to iboats.

 

[SeaKing15hp]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Hey fellow kentuckian, and welcome to Iboats. <br /><br />Chinewalker is right. (As if you needed me to say that)<br /><br />-Jacob

 

[ezeke]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Just in case you missed the drift, if the hub is spun, the prop is useless. <br /><br />A prop shop can fix it, but unless the prop is otherwise in excellent condition you will be better off with a new one.<br /><br />Among others, iboats sells a really good 3 blade aluminum prop made by Michigan Wheel (#012008), which I've found to be very serviceable. <br /><br />I have six of the 9.5 series motors, and (for what it's worth) I personally recommend the prop.

 

[whywhyzed]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

You've had this boat underway at some time before?<br />If you just put this boat and motor together, it could be the transom might be a 20" and the motor a short shaft or 15"... i.e. the prop isn't deep enough in the water

 

[Tye2791]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Thanks for the welcome and all the great info. The engine has run great in the past and just started this the last couple of times that I've had it out. Looks like a new prop is in order. Thanks again.

 

[Tye2791]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

OK, another dumb question. I'm looking at a new prop, but don't understand the differences in pitch (e.g., 6 1/2 vs 7 etc) Can anyone explain this?

 

[Vic.S]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Prop sizes are normally diameter X pitch.<br /><br />The pitch is the theoretical distance the prop will screw forward in one revolution. Fast or planing boats will need a prop with a large pitch because they will travel further for each revolution. A slow displacement boat, eg a sailing boat, will need a prop with a much smaller pitch as it will travel a much smaller distance per revolution. <br />For the extreme case of a high pitch prop take a look at that on a really highspeed racing powerboat.

 

[ezeke]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

The 9.5 series was delivered new with OMC propeller #383315 - 8 1/8" X 8". It is a three blade aluminum prop. <br /><br />The closest thing on our hosts' site is the one that I mentioned earlier. It is good match for this motor for all around use.

 

[jtexas]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

Are you sure this motor has a slip hub - I thought it was a non-thru-hub exhaust and a shear pin instead.<br /><br />tye, you're saying the motor revved while in gear, without pushing the boat, right? Is this just while you were moving through vegetation, or all the time?<br /><br />Weeds or leaves on the lower unit can disrupt the flow of water over the prop causing cavatation, giving you those symptoms, but then it should run all right after it's cleared. Are the prop blades in pretty good shape?<br /><br />Are you sure it's not popping out of forward gear? <br /><br />The bent pin--that's the shear pin, between the propeller and the motor, right? How bent is it? Try a new one, see if it works.<br /><br />Go to www.evinrude.com click on "parts & accessories" then "engine diagrams" they'll have a schematic for your motor and a parts list showing the prop size that came with it.<br /><br />good luck, and welcome to the forums<br /><br /><br />[note-the link to evinrude.com had an extra comma, sorry, my bad, it gets you to the same place as Vic S's link below...thanks, vic]

 

[ezeke]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

It has both. <br /><br />The earlier prop was very similar (#377635)- 8 1/4 X 8 1/2.<br /><br />Superceded in 1969 by 383315 - 8 1/8 X 8, and in 1973 by #385940 - 8 1/8 X 8

 

[Vic.S]

Re: 68 9.5 Horse Johnson Engine runs, boat doesn't go

The evinrude.com link doesn't seem to work. What you need is the BRP parts catalog at http://epc.brp.com/default.aspx?brands=ej&lang=E