Loss of power

[Bloggsy]

I just spent 3 weeks away fishing and the outboard went fine for the first week then one day after coming back from 20 K out I pulled up to let my mate drive the last 5 k and the motor would not reach full revs (would only do about 2500 rpm it seemed to be like a lack of fuel)
Tried re starting and even switched the battery off and on again but no change. So limped back to ramp.
As luck would have it I had a full set of filters with me, I changed the water trap and the low and high pressure filters as well as the spark plugs to be sure.
I cut open the low pressure filter but it was quite clean so assumed that the water trap filter may have been the issue although the bowl was clean and no water (I didn't have a hacksaw to cut it open)
Took the boat for a run and all went well for the next 8 days.

Then heading back in after having done 38 k I stopped for one last fish and when I re started had the same issue but this time after selecting neutral and then forward it was fine and didn't miss a beat.

So just wondering if you have any idea what the problem could be or if there is items that you suggest that I replace as a matter of course that may rectify this issue.

[Moonlighter]

Possibly the neutral throttle switch is playing up.

When the ECU receives a signal that the engine is still in neutral, it will limit engine revs to under 3000 (about 2500 from memory). The ECU cuts spark, limits spark advance and fuel. The result is like when a race car is in the pit lane with the pit lane limiter activated. The engine runs and sounds pretty bad once it hits the preset limit.

If you try revving the engine I neutral, this is what it does.

There are two of these switches, one in the throttle binnacle and one in the engine.

I think it's the one in the engine that prevents revving in neutral. If I am correct, the one in the binnacle simply prevents the engine being started unless it is in neutral.

They can get out of adjustment, or can fail. Only cost about $35, I believe, and not too difficult to change. A service manual will describe how to adjust or change.

Given the circumstances and symptoms you described including the fact you changed in and out of gear and it worked again, this does sound like a possible cause.

[Bloggsy]

Thank you for the prompt reply yes that does sound feasible as it has always been after the throttle has been returned to neutral by the way I should have mentioned that it is a DF175 2009 model

[Bloggsy]

Hi Moonlighter I just had a look in the repair manual and it says that the neutral switch is used to detect when the gear shift is not in neutral and prevents the starter motor engaging.
However the shift position sensor (in the same area on the motor) detects when the shift is in neutral and prevents the fuel injection from exceeding 3,000 rpm. This unit has a variable resistor that changes with the shift position.

So we are in the right area but do you agree that it may be the SPS not the neutral switch that may be faulty?

[Moonlighter]

Yes, that would be the one.

[Bloggsy]

Update

O/K I have replaced both the neutral switch & the shift position switch. But I have not been able to take the boat out to see if this has fixed my problem yet. I did however purchase a diagnostic tool and it shows the following faults:
SP Sensor failure X 1 time
CKP Sensor failure X 3 times
Overheat gradient X 2 times
Once at 1625 rpm cyl temp 104 c exh temp 104 c failure at 102 h for 2 min
Second at 813 rpm cyl temp 92 c exh temp 71 c failure at 248 h for 2 min

As I have replaced the Shift Position sensor that is not an issue (although I have had the low rev issue twice)
But should I also replace the Crankshaft Position sensor as it has thrown a fault. I assume that the part No. for this is 32160-87J10 or 32160-87L00 (depending on engine serial No.) and called a Coil Ignition Timing in the parts book. And could this also be the cause of the fault that I am chasing?