2012 Suzuki DF175A dropping RPM at speed

aok47

Seaman
Joined
Apr 18, 2004
Messages
52
New to the suzuki 4-strokes and facing the following situation.
While on the plane and increasing RPM to 4,000RPM the engine dropped rpm to 3500RPM, as I pulled back the throttle slowly the rpm would increase again to just under 4000RPM until it decreases further inline with pulling the throttle back further. Did this a few times, then it went away but returned when i tried to go past 5000RPM. This time it dropped around 300RPM which it picked up again as i pulled back the throttle again.

I'm getting no alarms and no error codes when i plug in the diagnostics, i ran the std checks through the diagnostic software and no issues.

So far i focused on the fuel systems and changed fuel filter (no visible water in the clear bowl) and primer bulb, also drained the fuel pump (drained fuel was debris and water free), also checked the spark plugs and they looked fine.

Today i took the boat out and was able to hit WOT a couple of times but majority of the time it would drop RPM when i hot 5000RPM.

Appreciate any help, not sure where to from here...
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,109
I would monitor the rail pressure to see if that is changing when this happens/
if that stays steady maybe you have an injector acting up
 

aok47

Seaman
Joined
Apr 18, 2004
Messages
52
to monitor the rail pressure i'd need it plugged into the laptop when running correct? (I have analogue gauges)

I moved up the fuel system today checking the low pressure fuel filter, there was 1/4" of rusty coloured water. I'll change low & high pressure fuel filters, and also pull apart the fuel pump to check internals and suction filter.
 
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