2000 mercury 240 efi to inject or not to inject

[Hemicar]

Have a 2000 speedster that was purchased with a bum motor (240hp efi) upon disassembly found a pretty tore up cylinder. (Knocked the sleeve out) was able to save the block with a new sleeve and hone to the rest. When I pulled the crank the original plastic oil pump gear was broken. I'm heavily questioning putting the revised parts back in or just doing the bypass and not have to worry about it. What would you do starting from square 1. Thank for any input

 

[ripcuda]

I removed the oil injection on my 240efi and have gone to premixing. As a recently purchased, new-to-me boat... I don't know the engine history (although looks to have been replaced once) and worry about the untold age and wear on the oil pump plastic drive gear. I will say premixing sux. It's a hassle and you use a lot more oil vs oil injection and the engine smokes some at idle (worse with cheap 2-stroke oil).

If I was rebuilding an engine and could ensure the questionable plastic gear was a) new, b) an updated revised part... then I'd very likely keep oil injection.

You figure... the original plastic gear lasted how many years? At what age did these plastic gears start failing more commonly? 10-15 years after built? The new, revised one should last at least that long, right?

Cheers!

 

[paulc229]

I have a rebuilt 240, first engine blew due to oil pump gear failure, was rebuilt by quicksilver,(previous owner) plastic gear was replaced by I believe the improved brass gear, I did run premix for a bit, but with the size of tank a huge pain to pre mix, too much smoke at low rpm, went back to oil injection and will never look back. Smokes much less at low rpm/start up, and with the improved gear not much risk, if you look at the number of blown engines due to the initial plastic gear to number of engines made failure is actually not that common, and even less so with the updated gear my 2 cents

 

[Tim75]

Have a 2000 speedster that was purchased with a bum motor (240hp efi) upon disassembly found a pretty tore up cylinder. (Knocked the sleeve out) was able to save the block with a new sleeve and hone to the rest. When I pulled the crank the original plastic oil pump gear was broken. I'm heavily questioning putting the revised parts back in or just doing the bypass and not have to worry about it. What would you do starting from square 1. Thank for any input

The typical autopsy of a blown engine can be traced to:
Engine overheat.
Oil pump housing expands (outward and inward), locking the pump shaft.
Seized shaft and gear destroys pump drive gear on crank.
Engine is destroyed.

Happens in seconds. This was not every case, but some.
If Merc had made the shaft hole in the pump housing .002 inch larger, it would not have been able to seize the shaft.

Merc went to an electric oil pump that was controlled by the ECU. Not sensitive to engine overheat.

 

[bucwizer]

How much oil should they use per gallon of fuel when injected? I also am going through the break in process with additional oil added to the fuel tank. The oil in the engine mounted and large tank don’t appear to be changing levels. 6 hrs on new engine runs great, have used approximately 10-15 gallons of fuel. Is this normal consumption?