Logo
FULL SITE MENU

Mercury CT115 2015 Over-rev problems

L

landmyne

New member
Hello,
my mercury command thrust 115 (2015) has been having high RPM's (over Rev problems) after changing to a new prop. Sounds like a pitch problem but it's not. I replaced my bent and dinged 13P 16 diameter quicksilver prop with a Nemisis 4 blade 13P 13.8 diameter prop. Motor would easily goto 6000 rpm. At 4000 rpm i was doing 4.5 mph and would over-rev if I added more throttle. Changed to a 3 blade 13P 16 diameter stainless prop i got for cheap. Top speed 21 mph at 5000 rpm but would jump to 6000+ RPM easily if I wasn't careful. Bought a new quicksilver 13P 16 diameter and a new hub kit. Top speed 19 mph and would over rev to 6000 rpm. Last year with wide open throttle top speed was 25 mph at 5350 RPM. The motor never went above 5400 Rpm at full throttle. I'm wondering if I have lower unit issues? Any suggestions?
 
You said it would go 21 @ 5000 with the stainless prop, what was the speed at 6000 did it speed up? Stupid question but the prop is down in the water properly isn't it?
 
Since you have tried numerous props hub slipping is out. Looking at other possible problems since you didn't mention changing anything else, one has to assume that you changed nothing else that would affect the prop to water interface.

Shift linkage not completely engaging could be a culprit. Another possibility is a problem with the spring in the clutch dog (mounted on the prop shaft) weakening, or possibly due to sloppy shifting you may have done (don't know how you operate your boat), or the poor engagement mentioned, the sawtooth gears between the dog and F gear may be worn off....rare but had it happen to me on older purchased boat.
 
Swagonmaster said:
You said it would go 21 @ 5000 with the stainless prop, what was the speed at 6000 did it speed up? Stupid question but the prop is down in the water properly isn't it?
Click to expand...

Didn't gain speed when it over rev'd. Top speed with the aluminum prop was about 26 @ 5400 RPM. Yes the motor was trimmed in the water correctly. Brought it to the mechanic. He thinks the clutch dog and the forward gears have had some edge wear causing it to slip.
 
Back
Top