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No power at wot mercury thunderbolt 50hp

C

Chadster34

New member
So I bought a boat last summer so I don't have much history on it
Boat started off great and I had a couple hour ride then ran out of gas
I finally got fuel but couldn't get proper motor oil so I used 2 cycle engine oil I know a no no but I figured something was better than nothing to make it back to the dock
During which I lost wot power I initially thought fuel supply
So I took apart my tank found a leak in the tubing into the tank so I fixed that
Now the ball is firm when squeezed and doesn't lose pressure
Checked compression 140 in all cylinders
Got the carbs cleaned by a boat guy not a professional
Changed plugs
Still had no power so I got a parts motor and swapped the carbs from a motor I know was running decently
Still no change
Took it to someone else
Changed stator and switchbox from the other motor
No change after
Checked resistance on coil packs and all within spec
Finally took it to a Merc outboard shop
They said 1000 to fix I needed a new stator and switch box
I decided to just do it myself so I'm in the process of that now but figured while I'm in there maybe replace the trigger as well ... Thoughts?
After all this I don't really believe that the ssue is all of the above
As the motor will run full rpm in gear out of water doing this quickly of course with muffs on
In water it doesnt go to high rpm in Just doesn't rev up
Could this just be my prop any ideas ?
Sick of blowing money on this motor
 
Chadster- I am going to assume you put 4 cycle oil in the motor in a pinch. (not 2 cycle as stated). This could be your problem as the fuel pumps are integral on both carbs. You may have to rebuild with proper kits and rebuild the carbs at the same time. While you are at it replace all the fuel lines and check all the wiring for missing insulation. Those motors (year classes) are notorious for poor wiring. Great motors otherwise. I know this well as I have one about just like it. Yours sounds good in the film clip, but it is hard to get much info from that.. Mine wouldn't go near as hard at WOT and it needed a new Stator and wiring harnesses. Then I needed to properly rebuild my carbs. All takes time and money but I have a great 50 TBolt now. Your motor's running condition on muffs will tell you very little. It needs the resistance of real conditions to find out if it needs help or at least someone with the knowledge of diagnostics and the equipment.
 
Do a spark test make sure it jumps 7/16" air gap. Revving up in gear on muffs means NOTHING. And you need to get that 4 strk oil out of there.
 
That motor " in gear " on the trailer is still in neutral.-----That wee prop does not have any load on it.-----And do not do that wind it up on the trailer thing.----Not good for the motor !!----Serial # is ?----Not sure why folks want to replace electronic parts without some testing first !!
 
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7154434 Is the serial number

I thought if a stator goes bad it fails completely not just lack power
I took it to three marine mechanics to do the testing and
One said he thought it was the reed valves after doing the carbs the other was unsure what caused it and the Merc marine mechanic said stator and switch box and go from there
I'm not convinced on any of it as swapping electronics etc.. has made no change
I would have at least thought it would get worse or better
Hopefully after the stator change it works
I ordered this stator but it doesn't seem to fit around the outer ring of the trigger

JETUNIT Genuine outboard 9 amp Stator Assy Maganet Coil For Mercury 30-85hp 3&4 cylinder 398-5454 A21 A22 A24 A25 A26 174-5454K1 https://www.amazon.ca/dp/B06ZZSTJF1/ref=cm_sw_r_cp_apa_i_FVd1Cb13G51XE

As far as I know I have a 1980 50hp thunderbolt based on my serial
Is this just a bad design of part ?
 
Have to ask.-----Is there an oil injection unit ( autoblend ) used with this motor ?--Does the motor have brown copper coloured deals ??-----Worked on a similar issue on a 50 hp some time ago.-----Shop installed all new electronics.-----Turned out the exhaust tuner was 3/4 plugged with carbon.-----Time to find a shop that knows how to test and diagnose I think !!
 
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Thanks for the info I don't believe it's that model
Sn is 7154434 where exactly was the exhaust tuner that was clogged ?
I took off the foot and looked up but it seemed to be clean .
Yes I agree on the shop I'm just soo sick of wasting my money on shops
That really haven't accomplished but but steal my money so
I'm giving it a shot .. thanks everyone for their help
 
I tried the serial number provided and it didn't work in the part lookup so I could verify my answer.

If I am correct your motor's CDI has two sets of windings from your stater.
One set of windings is used for starting and running up to about 2000 rpms.
The other set of windings is used from 2000 rpms to WOT.

If the CDI and the Stator doesn't match you will have a problem.
It is not uncommon for the high speed side of the stator to fail. You can test the stator with a DVA meter or a DVA adapter for your meter

There was a period of time when insulation on the wiring from the stator and the triggers were dodgy. It got brittle and failed.

Hope this helps, the correct parts are essentional...
 
Did you find a resolution for this issue? I found the key in the water pump was installed incorrectly and the shaft was hard to rotate, we fixed that but took the boat out today and it is still going slow on the lake as well but goes high rpms in nuetral. Also replaced many parts including the stator and CDI box, I am baffled by this outboard and this issue.
 
High RPM in neutral means nothing.---What actual trouble shooting have you done.----Compression test values are ?----Spark on all 4 cylinders ?-----Carburetors clean and fully opening ?-----Fuel pump diaphragm checked ?-----Exhaust blockage ?
 
Replace spark plugs and clean main carb jets. Should have been the first thing you did after running gas with motor oil instead of 2 cycle oil. If that does it, won't you feel pretty silly? Can't believe you've thrown this much money on that motor.
 
Usually it only takes 15 minutes to determine the issue with a poor performing motor.-----Fixing it is a different matter.
 
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