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Can a spun prop be intermittent?

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billythegrape

Regular Contributor
85 force 85. Finally got it fixed at the end of last season thanks to Jerry.

The boat goes along fine for about 20-30 minutes, then it acts similar to having a spun prop. Essentially, rpms increase while speed markedly decreases, excessive vibration, etc. Let it sit for a while, then it acts ok again.

If you have seen any my other posts, this engine is a bit of a nightmare anyway, it runs and drives now, but still hates to idle.

Could a spun prop act intermittently like this?
 
The motor is mounted in the only position it can go on this boat. There is no adjustment. It's a long shaft motor, and this definitely has to do with time on the water.

Don't some props reharden after they sit if they're spun?
 
???----Did one years ago.-----Told owner over the phone to measure the transom.-----He insisted on having the gearcase inspected.----Nothing wrong with the gearcase internals.--------Told him to cut the transom down 1 or 2 inches.-----No more complaint after that.----So post the height of your transom !
 
I'd be happy to do that but maybe I am being unclear. The transom is like 12"x 12", tapering to about 8" at the bottom. If I cut it, I'm afraid what's left will not be strong enough for the weight of the engine. It's just a tiny little wooden trapezoid. Won't this be an issue?
 
billythegrape said:
I'd be happy to do that but maybe I am being unclear. The transom is like 12"x 12", tapering to about 8" at the bottom. If I cut it, I'm afraid what's left will not be strong enough for the weight of the engine. It's just a tiny little wooden trapezoid. Won't this be an issue?
Click to expand...
He’s not asking the 2 dimensional measurements of the transom. The important measurement is height. Measure from the bottom of the boat to the top of the transom. In the video above, it would be from where the guys finger is pointing to the silver metal lip the motor sits on.
It’s important for the prop , so it doesn’t cavitate.
 
Also what's the bottom technically, the bottom of the tube thing the transom is attached to, or the bottom of the pontoons, or the bottom of the deck?
 
“Also what's the bottom technically, the bottom of the tube thing the transom is attached to…”
Not sure what you mean.
Size your photo to under 1Mb & it will post. It may look like a thumbnail, but if you click on it, it comes up full size.
Voila
 

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On a toon!! That makes a difference.
Google: how to measure a pontoon and outboard for the cavitation plate

Open the video and that should show you the right way to measure it.

Missing the skeg!! that makes a difference in the way it handles.
 
Jerry,

I had to look up what a skeg is. It says it only affects steering and prop protection. Since I don't have steering issues, should I even worry about it?
 

This guy says to set the motor at least 4" below the waterline. If I drop this engine more than an inch, I'd have my steering cable laying on the aluminum surround. See the photos above to see what I mean.
 
Wouldn’t spend someone else’s money, but we carry a spare prop and the couple tools to change it.

I thought I had a similar problem and took the prop to a local rebuilder. They have a jig for testing the hubs.
 
Now that I've looked at the pics again I see the problem.
When you said if you moved the motor down it would hit.
You have a short shaft motor(20") on a boat that needs a long shaft(25").
 
Jerryjerry05 said:
Now that I've looked at the pics again I see the problem.
When you said if you moved the motor down it would hit.
You have a short shaft motor(20") on a boat that needs a long shaft(25").
Click to expand...
Jerry,
I would think any problems caused by a motor being too short would be consistent, not happen after 20 min of driving. It is totally fine otherwise.
 
Unless I could see it?? then I'm guessing.
Take the prop off: mark the hub go for a ride make it spin, to see if it stays in the same position?
 
Before that. Remove the prop, scribe a line on the hub.
Reinstall and go for a ride, make it slip.
Then check the scribe marks.
 
Took it to the prop shop. He tested it, and it's spun just enough to cause the symptoms I described. There is one prop mad by one company available in the US. It's $200. You know what else is $200? A non running Evinrude 135. Can you guess which one I'm going to pick?
 
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