18hp evingrude fastwin slipping?

[screennamie]

On the maiden voyage of my 1953 alumacraft and 72' 18hp fastwin this happened. Right around the 36 second mark I think it slips out of gear.

She ran flawlessy for about an hour then I slowed down and turned off to fish for a bit. Started right back up and pulling away this is what happened.

Is it slipping or does anyone think something else could be wrong? is there an area to check or something I should be looking for if I pull her apart?

I took a pic of the gear oil too and that wasn't milky at all. Just unscrewed it a touch to get a few drips. Here's what it looks like, no metal shavings or anything either, just dark.

 

[nwcove]

Re: 18hp evingrude fastwin slipping?

sounds like a classic case of a spun prop hub, remove the prop, put a mark on the gearcase end, from the inner most to the outside. run it again till the symptoms occur. remove the prop and check to see if the mark"s" still line up.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Sounds like a good idea.. What do I do if they don't line up anymore? What should be replaced?

 

[F_R]

Re: 18hp evingrude fastwin slipping?

Agreed. If it grinds and jumps, it is a clutch dog. If it just slips like spinning your wheels on the ice, it is the prop hub. -----OR---- a sheared propeller drive pin. But a sheared pin won't drive the boat at all.

----SO, do as suggested, mark the prop. But you don't have to take it off to do it. Make a mark on the plastic nut and another on the propeller, aligned with the first one. Test run till suspected slippage occurs, stop and look at the marks. If no longer aligned, it slipped.

EDIT: This assumes it isn't cavitating (air around propeller) Like would happen if you are doing something dumb like running a short shaft motor on a long shaft boat.

EDIT EDIT: If it is slipping, you can take the propeller to a prop shop for a new hub. Or you can buy a new prop.

 

[nwcove]

Re: 18hp evingrude fastwin slipping?

either look for a replacement prop, or the better option is to find a shop that rehubs props. ( not to expensive to rehub, and the better option)

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Thanks guys. I'll be doing this tomorrow for sure. I read on another forum too that the engine will grind or shake if it slips out of gear. It just revs real hi like spining tires on ice.

How much do the prop hubs or part to replace them usually run? I've got a part manual for my motor but I don't even see anything listed saying 'prop hub' is it actually a piece of the prpeller?

Thanks again. I do know a place, I'll see how much they'd want to rehub it.

 

[F_R]

Re: 18hp evingrude fastwin slipping?

They are not sold separately because it takes special equipment to change them.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Bummer. So if I take my prop to a parts/marina store they're gonna want me to buy a new one I'm guessing. oh well, time to go shopping.

 

[AlTn]

Re: 18hp evingrude fastwin slipping?

check iboat's prices on props

 

[F_R]

Re: 18hp evingrude fastwin slipping?

And compare with re-hubbing. Don't forget the postage is both ways if you send one off.
http://www.soderbloom.com/propellers.html

 

[kfa4303]

Re: 18hp evingrude fastwin slipping?

yeah, it can be a wash between getting a new prop and/or the old one re-hubbed. If you happen to have a prop shop near by that you can take it to, you might save a bit of money, but there's nothing wrong with modern replacement props either. Just make sure you get the right size. There should be some numbers stamped on your current prop. I believe the one on my '66 20 hp is a 9x10, or 9x9, but you'll want to check yours to be sure. Your parts manual will probably list appropriate sized props that will work. There are probably several different props that will fit, each with slightly different advantages and disadvantages (low end torque vs. top end speed).

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Yea I couldn't wait.. tee hee.

I was getting spin when I put it in gear and moved it with my hand. So I took it off and the shear pin looked fine. the inside was slightly askew so that was probably it. It had a certain angle and wasn't completely round on the inside.

I found a local joint about an hour out and they had some props already rehubbed. A new one was about 150 and I paid 90 for mine and got to keep the old one just in case. It still worked so I figure I'll keep it like a spare tire.

Next question is, how tight do I have to make the prop nut with the cotter pin? For now I just finger tightened it to line up with a hole and put the pin in. Is there certain spec it has to be or torque maybe, should I do one full turn with a wrench then back it off till the pin will go in a hole?

Just kinda OCD about that kinda junk, I'd hate to be the reason I ruin another prop by incorrectly tightening the nut. :facepalm:

And it's definetly not a short shaft motor. I'd say the part that planes the boat is about an inch to two max underneath the belly and well below the water line.

 

[HighTrim]

Re: 18hp evingrude fastwin slipping?

The props are properly installed by installing the prop/drive pin, then hand tightening the prop nut. After hand tight, advance the nut with a wrench until the cotter pin hole is aligned.

Do not back the nut off to align the cotter pin hole. If you do the SS drive pin will wear the inner hub of the prop, to the point of complete failure.

Properly tightening it will NOT allow the drive pin to float causing hub damage.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

ok thats what I did basically. I lined up the prop with the pin slid it on and wiggled till she set on it. Finger tightened the nut and put the pin in it. So I should be good.

Here is a pic of the old prop. Not only is it dinged up pretty good but you can tell the insides kind of angle a bit, there isn't even space all the way around it. I think the innards are brass not rubber but I dunno. Here ya go.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

I'm thinking it may have been cavitation too. the inside of the prop doesn't seem too worn. I don't know when my phone finally decides to email it I'll post that picture of the other side. How far below the bottom of the boat does that plate above the prop need to be and how much trim should I have in it.

Like I posted earlier it ran fine for about an hour and a half or so. Then I stopped and fished then it acted up when I was rolling away so to speak.

 

[AlTn]

Re: 18hp evingrude fastwin slipping?

FR's pic is what the inside of your prop looks like. Reread the second sentence in High Trim's post #13.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Alrighty, when I get off work this mornin I'll take the pin back out. Cause she's finger tight already I'll advance it to the next hole with a wrench and put the pin back in.

 

[kfa4303]

Re: 18hp evingrude fastwin slipping?

you want the anit-vent plate to be even, or slightly higher than the keel of the boat. These vintage OMC motor have kind of an odd, in between leg length of around 18" rather than the normal 15" short shaft and 20" longs shaft standards. As a result, you usually have to raise the motor a couple inches. You can buy/build a jack plat, or just clamp it as high up on your transom as you can which should get the anti-vent plate just about level with the keel (Be sure to a dd a safety chain just in case.) That's what I did with my '66 20 hp and it definitely improved the performance, particularly on the top end. I could probably get a bit more out of it I wanted to get a jack plate, etc...., but I'm happy with what I have (about 20 mph on a 14' tinny) In the future, you may want to hunt online for any replacement props. You can often find good used props on sites like ebay, aomci for about $30-$40.

 

[screennamie]

Re: 18hp evingrude fastwin slipping?

Ya I already found a prop for a decent price and slapped it on there. I actually measured from the vent plate to the bottom of the boat and it was 3 inches away. I had the fiance' help me and I got it up as high as it would go and cut that down to 1.5 inches. Better than it was but still low. I'm going to see if I can find out a way to raise it anymore. What's a jack plate? I thought about building the transom a little higher but not sure if that icnh is really going to be worth it.

 

[kfa4303]

Re: 18hp evingrude fastwin slipping?

A jackplate is just a gizmo that "jacks" up the height of the motor form the standard transom height. You can buy manually adjustable ones that work well for motors up to about 20 hp, fancy-scmancy remotely adjustable ones for 200 hp motors and/or you can make a fixed one out of angle aluminum. Here are couple pics, but there are many variations. Just remember to use Stainless Steel hardware on it.