Alarm sound on a 225EFI 3.0L

[bompapen]

I have a 225EFI in a DONZI 16. When I try to plane the boat iff I raise the RPMS too quick the alarm sound continuosly and only can turn off iff I idle or neutral. When I plane the boat slowly the alarm sound again but at 50 MPH. Then I stop and sound at lower speed 45-40 and keep falling , some times just cant plane the boat. I stop the boat and keep my hands on both heads no hot. The oil tank has no air. Fuel separator no water. Not over RPMS. Need help here.
Thanks
David Vil?

 

[CharlieB]

Re: Alarm sound on a 225EFI 3.0L

The clues here are when load is increased to a point, then the temp alarm sounds, and when load is reduced/released, the temp falls into an acceptable range again.

Low water flow while under load. Any time a cooling issue rises, it is good practice to service/inspect the water pump and impeller. While that may not be the problem in this instance, it is well worth checking out.

A compression test should be done, pay VERY close attention to the readings as I suspect that one cyl may be just a couple lbs different, altho cranking pressures are FAR, FAR less than cyl pressures when nearing FULL load.

As load increases so does cyl pressure, a 'slightly' bad head gasket may contain combustion pressure at idle and very light loads, yet begin to leak into the cooling system at greater loads, then displacing cooling water the motor rapidly begins to overheat.

AFTER verifying the water pump and a compression test, you may then decide to pull the cyl heads and inspect the gaskets.

 

[bompapen]

Re: Alarm sound on a 225EFI 3.0L

Thanks for the info. The engine also have a rough idle. At more rpm the fault gone. I test the compression a diference lower than 3psi all cyl. The engine run very strong at 50 MPH I hit the gas and the boat jump to forward an then the alarm. I buy a scanner and temperature sensors. I will change the impeller too. Hope solve this , Just can wait how much speed I can get with this project.

Do you think the holes for cooling in front off gearcase substitute a nosecone for a jack plate use?

 

[CharlieB]

Re: Alarm sound on a 225EFI 3.0L

If you are 'surfacing' your prop you are going to have cooling issues if you do not have a low water pickup.

Standard gearcase inlets have a nasty habit of sucking air when motors are jacked much more than the A/V plate running at the surface once at speed.