Spun prop – what causes this?

Twice now I have spun a prop. Ranger Z21 bass boat, 225 Etec. Does this mean I seriously need to start dieting again? Both times at WOT after up on the pad?

No, it just means you need to start catching smaller fish!

How many hours on the new and old one? Could possibly be a bad install of the new hub or a bad hub. May want to talk with the prop guy and see if there is a warranty.

No damage to the prop, I take it?

Nope no damage, call the Prop Shop they will re-do it. But I’m curious that causes this?

Torque. Hitting something with the prop will do it too. Its like a shear pin, made to spin before you damage your prop shaft or lower unit.

Like Robby said high torque and hitting objects are the usual suspects. However there are times when the exhaust runs too hot and overheats the hub. If it happens again I’d take a look closer at the motor.

Heres what I think it is, The older Evie/Johnson props were joined to the prop shaft with a shear pin with a solid joining between the prop shaft and prop blades in the casting. The newer props have a vulcanizing of rubber between the housing that goes around the prop shaft and the blades. I just broke the vulcanizing between the prop shaft and the blades because I hit some rocks and it broke that vulcanizing. Older Mercs have the same joining as the newer Evies/ Johnsons so I’ve been through a couple props because of this. If you rev the engine and it seems to want to go and the prop wants to bite water but doesn’t its the vulcanizing. I still have the prop that went bad because I could repair what needed to be done via a home remedy but its too hard to explain what that fix was via the site here. You may need a new or used prop.

munchy wrote:

Like Robby said high torque and hitting objects are the usual suspects. However there are times when the exhaust runs too hot and overheats the hub. If it happens again I’d take a look closer at the motor.

I remember some of the early etecs had the hot exhaust issue. Talk with your dealer and see if they have a TSB for it. A quick google search showed that a cooling reroute is done or etec specific props are available.

I have a 2015 etec 135HO that was overheating to the point that it melted the prop hub insert. That was a smaller barreled four blade prop. I switched props to a full size barrel and it solved the problem. I know that’s not a great comparison to your situation, but my etec was running some seriously hot exhaust through the prop without triggering a temp alarm. Food for thought.

Im just curious, why would an etec specifically blow hotter than usual exhaust:???:

nhamm wrote:

Im just curious, why would an etec specifically blow hotter than usual exhaust:???:

Not sure on the etec specifically but it could possibly be a symptom of running too lean, bad timing, a restriction in the exhaust, not enough cooling water, etc..

From the description john23 says it may just be too much exhaust for the hub exhaust port size and causing a restriction and heat buildup. Or like Blackbay says not enough cooling water for the size of exhaust tube and causing a buildup of heat.

I knew someone with a 225 evinrude that the hot exhaust issue.He went thru 2or3 hubs before they figured it out.Wish I could remember the fix.

heat could be either water pump or thermostat issues ,I know the bigger mercs have a stat on both sides of head they can fail or plug up with sand and makes for a hot running engine.

bassn7 wrote:

heat could be either water pump or thermostat issues ,I know the bigger mercs have a stat on both sides of head they can fail or plug up with sand and makes for a hot running engine.

Yes, but that would cause an overtemp condition in the motor first, not the hub.

I learned a bunch by this post. Thanks all. Ive always been a Merc guy.

It would make zero sense to me if the etecs have a hotter exhaust than other motors. Maybe it flows differently or something? The reason I tried the small barrel prop on my boat was that I have a buddy with the same boat and a 135 optimax. His opti liked that particular prop. It didn’t work for me simply because it restricted the exhaust. It was not the same issue that caused overheating in the early etecs (there’s a TSB out on that issue which resolves it, by the way).

I wouldn’t have known about the hot exhaust thing except that it eventually melted the exhaust ring which changed my hole shot. Once I switched props (which actually improved performance) I had zero issues. I still love my etec after two years of owning it.

john23 wrote:

I wouldn’t have known about the hot exhaust thing except that it eventually melted the exhaust ring which changed my hole shot. Once I switched props (which actually improved performance) I had zero issues. I still love my etec after two years of owning it.

Interesting. Buzz have all your props been aftermarket? Wonder how healthy that back pressure on the exhaust is to the engine if it really is restricting that much.

I can see prop makers really pushing tolerances to maximize performance.

Spun Prop? Could be worse Buzz! This unlucky tourney angler said he was just buzzing along and the boat came to a stop. Didn’t hit anything, just fell off.

Now that I’m looking at it a bit closer, I’m going to GUESS something was hit at some point. Might not even been the day off… the spindle is bent and lube is coming out of the seal.

Either way, I’d rather have a spun prop.

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@john23 We have a 2015 etec 135ho and had multiple spun props in the first year. It melted five different hubs before we switched to stainless steel. Then this year we are having a temp alarm going off at cruising speed 3800-4000 rpms. Dealer can’t figure out why.

The problem I had seemed to be that the exhaust was restricted coming out of the prop – I was running a small barrel prop. When I switched to a full size it went away. Make sure that you don’t have anything restricting the exhaust coming out of the prop. Also, they make water intake screens that are larger than the standard — that might help with your mid-range issue. You can buy them online and swap them out on the lower unit with a screwdriver.

Do you hole shot from a stand still? I always give light throttle first until 5 – 7 mph and then hit it.