Merc 60HP Bigfoot - Suntracker 21 Pontoon - Power Issue at Top End

RolyB

Recruit
Joined
Jun 2, 2016
Messages
3
Looking for help on a pontoon I recently purchased. I am running a 14 X 10p 3 blade prop. Initially at initial WOT the motor would get to ~5k rpm then bog down to under ~4k rpm. After I exhausted my attempts I had a mechanic look at it and he ended up cleaning/checking the fuel pump and VST. He also had the 4 injectors cleaned. After this work the motor now will hold somewhere between 4,800 - 5,200 rpm somewhat consistent meaning that it will fluctuate over some time between this range but really unnoticeable since the change is over a period of time. The result of this range puts me at a top speed (GPS) of 12-13 mph at WOT. Based on other threads that I have read with owners of a 21 Suntracker with the same engine typically report being able to hold 6k rpm and hold around 18mph. In neutral I can rev the engine to 6k+ with no issues. Here is what has been done.

New prime bulb
​Fuel filters cleaned
Fuel pumps checked
VST checked
Plugs changed (although the originals where Champion and the replacements were equivalent NGK, not sure if that makes a diff?)
Injectors cleaned





Looking for feedback on what I could look at next. Any help would be greatly appreciated.





Thanks!
 
Last edited:

turn2

Petty Officer 3rd Class
Joined
Jan 24, 2010
Messages
87
Did your mechanic clean the injectors or send them off ? If self cleaned by mechanic ,did he have the proper tools to test the flow? If not I suggest a flow tested set of injectors. I have had good luck on ebay. I have got the rebuilt ones.
 
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RolyB

Recruit
Joined
Jun 2, 2016
Messages
3
He actually did take them to a shop where they were cleaned and out through ultrasound.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Revving the motor in neutral like that means nothing, it can only lead to bad things, so best to not do it.
 

RolyB

Recruit
Joined
Jun 2, 2016
Messages
3
Thanks for the replies so far. Anyone think that plugs could play a factor on just the top end or would it affect the full range?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Thanks for the replies so far. Anyone think that plugs could play a factor on just the top end or would it affect the full range?

Not really, plugs get blamed or changed as a first attempt to fix things, they are rarely the real problem.
 
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