Evinrude E-NATION, for those dedicated to water, power, fishing and fun
Reply
Mate
Posts: 0
Registered: ‎08-07-2018

Inner Prop Burn

Hi All. I'm having difficulty figuring out a cause for the prop burn on my 90hp etec. Motor is 2015. Same burn patterns when using a 17 or 19 pitch aluminum Rebel prop. Engine is on a smokercraft 162xl, set as low as it can go. Anti ventilation plate is an inch above the bottom of the boat. WOT is 5400rpm running at 35MPH. I've tried a 15 pitch however I get a loss in performance. I'm wondering if it's a trim issue, as the burns intensify as I try to get on plane. I'm only getting the front 1/3 of the boat out of the water with a couple trim bump ups. Any more seems to add to the prop burn.

Anyone else experiencing similar issues?

Should I try moving the engine up a bolt?

Many thanks!
Admiral
Posts: 7,115
Registered: ‎07-14-2011

Re: Inner Prop Burn

By prop burn do you mean cavitation erosion near the base of the blades? If so, there may be nicks or gouges out of the leading edges of your gearcase or disturbed water flow coming off the hull.


From a propeller selection handbook:

 

Cavitation is caused by a disturbance of the water flow in front of the propeller.

 

An irregularity in the boat bottom or gearcase, a misplaced transducer or speedometer pickup, or even a loose rivet can cause this problem. Cavitation begins when a disturbance creates a low-pressure area in the water flow. As speed increases, the low pressure intensifies enough to vaporize (boil) some of the surrounding water. When the vapor bubbles approach a high pressure area, they collapse, releasing energy and causing damage.

 

The results of cavitation usually appear as burned areas on the gearcase or propeller blades. If the damage is substantial, performance is lost and the propeller should be replaced. In addition, the cause of the disturbance should be repaired to prevent further problems

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Mate
Posts: 0
Registered: ‎08-07-2018

Re: Inner Prop Burn

Thanks for the reply Bill.

Ya that's exactly what I've got on my prop. Pretty much happened right from the get go. My dealer couldn't figure it out, he's 5.5 hours away so not really an option to keep bringing it in to try different adjustments. Its on a trailer right now so I'll give the gear case a once over, as well as the bottom of the boat for any loose rivets.

Thanks again.
Admiral
Posts: 7,115
Registered: ‎07-14-2011

Re: Inner Prop Burn

Inspect the bottom of the boat from the keel to about 14" on either side of it and up to 4' in front of the transom for anything that looks different or suspicious. That is assuming the gearcase, skeg, and leading edges are not nicked.  You don't have a hydrofoil, whale-tail, or other type of plate bolted to the motor, do you?

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Admiral
Posts: 7,115
Registered: ‎07-14-2011

Re: Inner Prop Burn



Are there any thru-hull fittings, transducers, or pickups mounted to the transom and within 14" of the boat's and motor's centerline?

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Mate
Posts: 0
Registered: ‎08-07-2018

Re: Inner Prop Burn

Got a chance to check everything over. Nothing out of place on the bottom of the boat. Gear case and skeg are good. The fish finder transducer is 9" from the motor. I do have trim tabs also on the boat. The transducer location and trim tabs were set up by the dealer. This is season 2 of this boat and have had the issue since first time in the water.

Thanks again for all you assistance.
Admiral
Posts: 7,115
Registered: ‎07-14-2011

Re: Inner Prop Burn

9" is too close to motor centerline. Remove transducer temporarily, run boat a while, and see if burning continues.

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Mate
Posts: 0
Registered: ‎08-07-2018

Re: Inner Prop Burn

Thanks for the follow up. I'll give it a go.
Mate
Posts: 0
Registered: ‎08-07-2018

Re: Inner Prop Burn

I painted the prop prior to trying out the run with no transducer. The paint came off in the same locations and seems to be a little worse now.

Spoke with a yamaha/evinrude mechanic on the lake and he seems to think it's due to the hull construction/shape. Says I'm just gonna have to live with it, or swap the motor out for either a longer shaft etec or different brand. Says really I should bring it back to the dealer and let them figure it out, but it's a 6hr drive away...

My buddy has the same boat with a 90 merc and has zero prop burn issues.

Admiral
Posts: 7,115
Registered: ‎07-14-2011

Re: Inner Prop Burn

You mentioned that it is an aluminum Rebel prop. A Rebel prop is a stainless steel propeller, not aluminum.

What type propeller do you have, model aand part no,?  If aluminum, try a stainless steel model. Raising the motor is also something that could be tried as you stated that there is nothing obvious seen. 

 

Can you post photos of the prop burn marks and the transom?

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.