Will a new prop fix my problem.

[Bljc30]

I need a little help please. I bought this boat a couple years ago and I have had an over-rev problem since day one. Here is what I have.... 1) Performance issue you are trying to correct. Hitting 5500 rpm's at about 1/2 - 3/4 throttle, over-rev sensor shuts it down but doesn't kill the engine ( turn off the engine, starts right back up then runs fine as long as you watch the tach) 2) Current prop manufacturer, model, aluminum or stainless as a minimum. Aluminum 3) Current prop diameter and pitch (required). 12-1/2 X 15 X 305 all the numbers that I could find 4) Wide open throttle RPM and speed with an average load (very helpful). 5500 at 1/2 - 3/4 throttle , 21-22 mph 5) Engine/drive make, model, year, and HP Evinrude , E40TTLEUC , 4/97 , 40HP 6) Boat make model, year, length and weight. Bass Tracker , Pro 17 , 1989 I know that this motor was put on about a year before I got it. The last owner said that it was always like that. (doesn't make since) Do you think that by going to a 12x17 prop would fix this problem? I'm lost. I'm open to any advice offered. Thanks

 

[steelespike]

At 5500 with typical 13% slip speed would be about 28.
Is your speed by gps?
I don't think the motor has a rev limiter. It may have a runaway cutoff.It wouldn't cut in at 5500
The motor is capable of 6000 with no limiter or cutoff activating.
Does it suddenly shoot up to 5500 with no apparent speed increase Perhaps like it is slipping?
The Pro17 is 548 lbs. dry weight. All up its probably 1200 lbs or more.Not likely to over rev.

 

[buckinrut25]

I agree with Steele your slip is way to high. With the size and weight of the boat I dont think the prop is your issue. Sounds to me like the engine either has a spun hub or with the previous owner saying it has always done it. It's possible the engine is not mounted correctly and once you get speed up the prop is cavitating causing the over rev. With your boat and engine level check to see were the cavitation plate is running with the hull. A good place to start is to be sure your plate is either level or slightly below the lowest point. My guess is that once you get the issue corrected you will find that 15p to be over propped.

 

[Bljc30]

Is your speed by gps? Yes It doesn't just shoot up in rpm's. It climbs and increases speed until it hits 5500 and then it shuts down, not off, it won't go forward until you turn off the engine and restart it. If you watch the tach and keep it under 5500, it run fine all day. The plate is level with the hull and the motor is on the lowest mounting holes, so I can't move it down any farther.

 

[jestor68]

Try a different prop.

As others have indicated, it's possible that your prop's hub has spun, causing it to slip.

The prop selector indicates that a 13 pitch is appropriate and says to expect 5500 rpm @ 26-27 mph.

Your rpm range is 4500-5500 rpm.

 

[Bljc30]

Try a different prop. As others have indicated, it's possible that your prop's hub has spun, causing it to slip. The prop selector indicates that a 13 pitch is appropriate and says to expect 5500 rpm @ 26-27 mph. Your rpm range is 4500-5500 rpm.

So should I order a 13 pitch or stick with the 15 like it has now?

 

[Sea Rider]

Before throwing money into the blue wild guessing, perform a spun hub test to begin with, will know if prop is the culprit or not. Remove prop turn it over and mark with white marker a straight line border to border at center of prop. Put prop back, go for a wot spin for at least one minute, remove prop and check if line has moved to other position than straight drawn. If so, you definitely have a spun prop. Standard factory deliverded props on light to medium loaded applications should work satisfactorily.

Happy Boating

 

[steelespike]

I think he is saying at 5500 it shuts down not off and it won't go faster until he shuts it off and restarts.
I can't think of any normal feature that would do that.
I wonder if something under the hood is contacting a plug wire shorting the spark to one cylinder.

 

[Bljc30]

It shuts down as in it goes to an idle no matter where the throttle is until I turn it off and restart it. Then it goes back to normal until it gets to 5500 rpm's again. Like I said, I can run it at 5300 all day and no problems. But that is just 1/2-3/4 throttle and 20-21 mph.

 

[Sea Rider]

Does that model has an ECU ? If so, you should scan or make someone that knows its working parameters scan it for you, probably an ECU failure. Electronics can fail when you least expect them to do so. If not having an ECU, CD, Heat Sensor are probably going shot ?

Happy Boating

 

[steelespike]

That sure does sound like a safe mode kicking in.Perhaps in error
It is model E40TTLEUC a 97.This sounds more like a motor issue.
Certainly not over revving at 5500 rpm. Not likely it is actually 5500 as that would very likely produce about 28 mph.

 

[Bljc30]

Now I'm even more confused! LOL I don't really know any boat mechanics, so I'm going about this on my own. That is a dangerous situation, as this is my first outboard over a 9.5 hp. Going off of the advice of you guys, where do I start? Something electrical? Something more serious? Just trying to find a starting point if you guys feel that it truly isn't a prop issue. Thanks again for all of the advice.

 

[steelespike]

How mechanically inclined are you? have you ever rebuilt a carburetor?Do you understand basic 2 stroke outboard operation?
Do you have a factory repair manual?If you plan to try to solve your problem A factory repair manual is an absolute requirement.
Have you ever trouble shooter an outboard ignition system?
Do you know if the motor has an electronic control module?(an onboard computer control able to record operation and would have a safe mode that reduces speed if it senses a problem).This motor would probably have direct injection of fuel not a carburetor.
Have you looked under the hood?
Put the motor in forward with the motor off advance the throttle and observe the movement of the components.

 

[Sea Rider]

An outboard is a very complex water machine. I would start by doing the hub test to check if prop is still in 100% operational shape, costs nothing to detect. Can't be blamed to be the direct culprit but it's a good start. Prop hubs are not eternal, previous owner probably run prop against a sand bedl, which you don't know about. Does the prop has noticeable peeled paint on blades edges ? Go for a wot run lightly loaded and post your findings...

Happy Boating