Yamaha HPDI reliability compared to 4-stroke.

[AKrider]

Since Yamaha never dropped 2-strokes from their outboards, how well do the HPDI's hold up? I know very little about boat motors, but the few things I read on some boat forums indicates the higher output HPDI's don't hold up well. Guys write that 4-strokes are the way to go.

Since a boat motor has unlimited cooling, is it just impossible to build a reliable, high horsepower 2-stroke? I'm thinking it is.

 

[blueironranger]

Since Yamaha never dropped 2-strokes from their outboards, how well do the HPDI's hold up? I know very little about boat motors, but the few things I read on some boat forums indicates the higher output HPDI's don't hold up well. Guys write that 4-strokes are the way to go.

Since a boat motor has unlimited cooling, is it just impossible to build a reliable, high horsepower 2-stroke? I'm thinking it is.

IF you keep the fuel clean and fresh there isn't many issues with HPDI. The issues rise when an injector gets plugs, even slightly, and causes a lean condition. Same goes for the oiling system, the passages are so small that and little chunk of crap will plug a passage and starve a bearing if they use pressure lubed bearings. By the time you hear spark knock on a 2 stroke its too late, damage is done. Get spark knock on a 4 stroke and the engine is fine. I've seen many 2000+ hour HPDI Yamaha engines around, that goes for E-tec and Optimax also. That said, I run 4 stroke outboards.

 

[AKrider]

I wonder if the plugged injector is what caused some of the burn downs I read about?

Seems like for guys that complain 4 strokes are too complicated, they've not been paying much attention to the amount of electronics that are being added to 2-strokes. The EPA compliant 2 strokes bring a whole new set of issues to the table.

Is the Optimax an Orbital direct injection system?

 

[Vectornut]

This is precisely why I went to 4strokes plus the 2strokes are very sensitive to poor gas now being sold. Two of my buddies burned down their sleds this year (2strokes) and for no reason other than to question the gas quality. 05 Vector ER.