Spun prop - older 9.9

[Franko Manini]

Folks,

On a trip to the interior to do some fly fishing I grounded the prop on my mid nineties Evinrude 9.9. It got me through the trip but I am noticing some prop slip at higher RPS or when under heavy load (like with extra guys in the boat). I am 90% sure the grounding (against a rock at low speed) caused the prop to slip the rubber bushing. Is there somewhere in Victoria I can take it to get a new bushing pressed in or am I buying a new prop?

Thanks everyone

 

[scott craven]

Is the prop still in good shape or did the impact bend a fin ?
if damaged it might be cheaper to replace than repair

 

[SpringVelocity]

If you do go to Vic prop in cobble hill. Also make sure it not vibrating. If you lucky it's spun like you say.

 

[Filletandrelease]

I'd find it pretty odd that the rubber hub had sheared and not have any damage to the blades.

 

[BigBird007]

If you want to find out if it is slipping or not. Take the prop off, mark both the the hub and the outer section the rubber is valacanised too. Make sure your marks are inline. I use a flat chisel with a little hammer tap, doesn't need to be big marks but you need to be able to identify them. Reinstall the prop and take it for a rip, inspect marks after you run it, if they have moved you have a problem.

Sometimes you can take them off and visually see the rubber has been spun but not that common.

 

[Franko Manini]

Is the prop still in good shape or did the impact bend a fin ?
if damaged it might be cheaper to replace than repair

There is a minor chip on one fin. I wouldn't even bother filing it down. I was too busy watching shoals for big cruising rainbows and casting a tiny #18 dry fly to them when I hit the rock. Startled me, but it didn't bend the fin.

 

[Franko Manini]

If you want to find out if it is slipping or not. Take the prop off, mark both the the hub and the outer section the rubber is valacanised too. Make sure your marks are inline. I use a flat chisel with a little hammer tap, doesn't need to be big marks but you need to be able to identify them. Reinstall the prop and take it for a rip, inspect marks after you run it, if they have moved you have a problem.

Sometimes you can take them off and visually see the rubber has been spun but not that common.

I wish I had thought of this while we were in camp. It's a great suggestion. Of course, it is still tight enough that you can make the engine rotate in gear by turning the prop so that doesn't tell me much. But your idea is a good one.

 

[trophywife]

the chip can cause cavitation... plausible

 

[Tightlines22]

I've been reading this thread. Are you sure there isn't a shear pin on this prop? It's pretty difficult to spin a hub. Especially at slow speed as you described.

 

[noluck]

I've been reading this thread. Are you sure there isn't a shear pin on this prop? It's pretty difficult to spin a hub. Especially at slow speed as you described.

shear pins are used in solid props (usually under 8 hp), rubber hubs do not have shear pins.

 

[Rockfish]

A few years back I had an older HT9.9 Yammi in for repair at Forsch Marine near Sidney (a non dealer Yammi specialist shop). Among other things, the hub was spun and they replaced it with one that had already been to the prop shop for a new hub and a blade tune up. They got my old one to send for service and I assume it would go to the next guy. No waiting, as it was like a core return and reasonable cost.

 

[Franko Manini]

I've been reading this thread. Are you sure there isn't a shear pin on this prop? It's pretty difficult to spin a hub. Especially at slow speed as you described.

I'm certain. The rubber bushing is apparent on the prop and there is definitely no shear pin. If there was, and it was damaged, then I wouldn't get any thrust at all.

 

[Franko Manini]

the chip can cause cavitation... plausible

What would the symptoms of cavitation be?

This motor goes on an 11' inflatable. normally I can get that boat up to 30kph (GPS) and it's smooth a butter. After hitting that rock, I cannot get above 22 KPH and it has this weird sort of jerky surge that comes and goes. The surging only happens under high load circumstances. It feels like there the motor is dying out, just for a second, but it is DEFINITELY not the motor. The RPMs don't drop, it's nice and smooth, and the thing runs awesome. So is it a spun prop or cavitation? Maybe I'll take some pics of the little chip. Its so tiny but maybe that's all it takes?

 

[trophywife]

somewhat like a spun prop.. rpm fluctuates, less drive!!

 

[Rockfish]

Depending on how hard you hit, it may be worth checking out the leg. It would be easy enough to change the leg gear oil and see if it has that muddy milky coffee look from water getting past a damaged seals for starters. You may need a new hub but bent leg parts,or a bad bearing or seal can cause problems which only get more expensive with use. Also if the hub goes completely at speed, the motor is no longer under load and the RPMs could spin up instantly which may not be good for the motor, especially 4 strokes, unless it has some sort of computerized rev limiting cut out to protect the power head like I believe some of the bigger modern motors have. Hub replacements and blade tuneups/balancing by a prop shop are not expensive and if that does not solve the problem you know where to look. They may even tell you the prop is fine but that may not be good news given your symptoms.

 

[Filletandrelease]

I am thinking cavitation. If that hub is broken it will tear itself apart real quick

 

[lazylump]

I've spun about 4 hubs over the years. Usually it happens a little while after I get a chunk of cedar bark or something stuck between the prop and the ventilation plate. Typically I can almost get up on plane and the prop will spin out and you lose momentum and the water will boil and make a terrible noise, then you can then limp back in at lower speeds.
My son drove over a rock before and took 1/4 to 3/8'' off the tips, I took the prop in to Rev in Nanaimo and he welded on new tips and painted it for half the cost of a new prop, good as new. It's worth it to take your prop in to get fixed. They can also be tested to see if they are spun in the shop, I don't live in Vic so I have no suggestions, but there must be several down there. I would buy a spare if you don't have one.