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Mate
Posts: 3
Registered: a month ago

2008 250 E Tec prop hub issues

I keep melting the TBX Hub Busshing at top speed, have went through 4 in the last 2 years, I was told to back flush the cooling system still melted on this past weekend. is there another hub kit I can use? and do I have more serious issues if I keep it around 4000 RPMS I am ok butv when i let it eat the hub will melt out within a few miles.

HELP!!!!!!

I am running a 14 1/2 x 26 Raker 2

Admiral
Posts: 5,736
Registered: ‎07-14-2011

Re: 2008 250 E Tec prop hub issues

[ Edited ]

 

Something is causing the extra-high exhaust temperatures required to melt the TBX hubs.  Over propping is one cause as are plugged up cooling water passages in the exhaust is another. Is the motor jacked up or trimmed out too high to prevent a solid flow of water through the engine? 

 

What is the engine water pressure at each 1000 rpm increment and how does that compare with the published specifications   -  your dealer should check this.

 

Did someone remove the trim tab or is the trim tab hole and passageway blocked with mud, shell, etc?

 

Is the hose, fittings and passageways on the back of the engine block that goes into the mid-section clean and flowing water without restriction?

 

What is the top rpm of the engine at full throttle with a full tank of fuel and a normal load of passengers?

 

Is the exhaust sensor pressure tube clean and in good condition?

 

What are the engine temperatures on both heads at idle, 40000, and WOT?

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


"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. If you elect to do it yourself, be sure to use caution, common sense, and to observe all safety procedures in the vicinity of gasoline, moving engine parts, high temperature components, heavy items, and 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: 3
Registered: a month ago

Re: 2008 250 E Tec prop hub issues

The prop is stock I believe, and as far as water presure it seams to be good throught out, I will check this weekend and record the presures. I did install a 6" jackplate this year but i had 2 hubs go before the jack plate, I have not had the chance to fine tune the jackplate heigt as of yet because i am unable to run much over 4000RMP for fear of melting another hub. it is curently at about the same height as it was when it was on the trasom just back 6" further,

What is a good Measurment to start at on height? as said before water presure is fine as is.

When i back flushed the motor i had good water flow out of all the pick up areas except I expected to see more come out through the exaust inside the prop, there was some but not alot.

WOT is around 5500 rpm, I seldom run much over 5000 this gets me around 70MPH and that is more than fast enough for me, i do not think i am over trimming it as there is no noticable roost and i keep the rpms in check.

there is no trim tab, ill check the tab hole tonight.

Is there a better way to flush out the cooling system, I hooked a garden hose with moderate water presure to the fitting on the back of the motor, I did have water coming out from under the small covers on both sides just above the cavitation plate and a small amount out of the seam where the lower unit bolts up.

I ll check and record engin temps this weekend as well

Thanks

 

Admiral
Posts: 5,736
Registered: ‎07-14-2011

Re: 2008 250 E Tec prop hub issues

 

 

Have your dealer refer to the annual Service Update Booklets for assistance in troubleshooting the melted hub problem.  Page 110 of the 2009 booklet gives some hints and procedures for eliminating melted hubs. Pages 110 and 111 of the 2008 booklet also address the problem. An excerpt from the 2008 book is below.

 

PROP HUB COOLING
Outboards may experience prop hub failure for many reasons, such as:
• High jackplate settings
• High transom mounting heights
• Aerated water conditions
• Restricted exhaust cooling water passages
For outboards experiencing propeller hub failures, check cooling system operation
and water pump condition. Refer to 2008 Water Pressure Chart on p. 103.
Check trim tab and gearcase water passages. Passages must be open and
unrestricted for proper water flow to propeller hub area.
The trim tab passage supplies water to a tapered passage in the gearcase. The
gearcase passage provides water to cool the exhaust. If these passages are
plugged by mud or other debris, high exhaust temperatures can damage propeller
hub or hardware.
The tapered passage starts at about 5/16 in. (8mm), ending at 1/8 in. (3mm).
This passage may be drilled to the larger diameter to increase water flow.

 

If additional cooling is needed, a 0.125 inch (3,175 mm) hole may be drilled in
the center of the lower inner exhaust housing extension.

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


"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. If you elect to do it yourself, be sure to use caution, common sense, and to observe all safety procedures in the vicinity of gasoline, moving engine parts, high temperature components, heavy items, and 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: 3
Registered: a month ago

Re: 2008 250 E Tec prop hub issues

k last night i pulled off the cover where the trim tab shoud be and blew out the water ports , No problems there. went over all the water intake areas on the lower unit . all seam fine. hooked it up to the garden hose at the backflush fitting on the back of the motor had good water flow coming out every where except out of the prop, just a small amout comes out of the inside of the prop. is there a way I can back flush this area only? it seames this may be my problem.

Admiral
Posts: 5,736
Registered: ‎07-14-2011

Re: 2008 250 E Tec prop hub issues

[ Edited ]

For a more thorough backflush remove the gearcase and thermostats temporarily.

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


"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. If you elect to do it yourself, be sure to use caution, common sense, and to observe all safety procedures in the vicinity of gasoline, moving engine parts, high temperature components, heavy items, and 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.