Engine lacks power.

Hello all,

Have a 2003 90hp 4 stroke. Engine starts and runs ok, except it makes no power above half throttle. The engine was just put onto the pontoon after being bought from an auction. I was told that the engine was dropped on its side prior to going to the auction. I dont seen any damage to the motor upon visual inspection. What are some things that would cause it to have no power above half throttle? It does not cut out or run rough above half throttle, it is like there is no response at all from the motor.

Thanks

whats the top rpm?

Do not have a tachometer, but it seems like it is topping out around 2500rpm. When the throttle on the boat is wide open the engine speed doesnt change at all after half throttle.

Do the RPM's rise but no extra speed or does she just labour? If the first possible spun hub,if the second over propped.

The RPM's dont rise whether the engine is under load or not. Max RPM I am getting is around 3200 (Got the tach working now) and that was one quick run up in neutral.

Is it a honda or yamaha or did you build it in your garage?

2003 Mercury 90hp 4 stroke

is it getting to 3200 with the control arm about where it should be for 3200 and then when you give it more it just stays at 3200 or is it with the controls all the way?is the advance smooth and linear from idle to 3200?
you could have a control cable adjustment out of whack...or you could be failing to advance timing...

check the filters

Hi all,

I have a 2003 Mariner 200 EFI. 3 weeks ago the motor was working perfectly well when all of a sudden after I went back to neutral after a good run, I gave full throttle and the motor wouldn't rev more than 1800 back to port and was overheating all the time during the way back. I took it to the mechanic, he checked oil tank in motor including sander and replaced it cause on the computer it was sending signal that no oil was in the tank wen it was full so thought might be that, but it wasn't after we retried in sea. Now eliminated the extra water separator in the boat and managed better to 4000revs with trim help though. Impeller, oil and the other general servicing stuff was done as well an even checked coils for bridge sparks and injectors all well but to no success. We also tried to replace the airflow senor TPS but remained the same. The motor works fine no strange sounds coming out. When Neutral I give it gas the rev goes to 6000 no trouble although after I take foot of peddle after giving full gas on neutral sometimes the motor turns off like no fuel but fuel is going to the motor because the manual pump gets hard immediately when i pump it. Its when it has the load that it's like doesn't have strength to develop more than 4000-4200revs max. I'm goanna change mechanic but it's like no one can understand what the problem is.

Can anyone be kind enough to help me please.

Sound like you lost a cylinder/s either: compression, or CDM module. It wil rev to 6000 rpm with no load on 3 cylinders !!! The overheat may damaged the cylinders

Any way I can be certain of that? like a particular test run at sea and remove plugs one by one to see performance?

we have two threads working here...that's a no-no...it just confuses things and neither problem will be properly addressed...burt1986....you need to open a separate thread...thank you...

OK sorry

how exactly do I do that please