Not sure on the 10% rule but that’s what I had always heard.

Back in the old days, OMC’s said on their ID tag, “OBC” rated horsepower.

Outboard

Boating

Club (of America)

Merc didn’t do this and stated whatever they wanted.

That was the begging of the horsepower wars.

They we’re advertising 18 hp, 20 cu in motors as 10 hp against OMC’s 15 cu in 10 hp motors.

To the OP’s orig question, the HPDI Yammi 2 strokes didn’t have a very good reputation and I don’t think production lasted very long.

I liked the design but had no first hand experience w/them.

A few yrs back a saw a bass boat at a ramp w/one and I quizzed the owner.

He had recently bought it and was a rebuild.

He had also spent a fair amount of $$ on it to keep it up.

Said it was making the new motors (Merc 4 strokes) look good to him.

I think you could apply his story/experience to every 2 stroke I’ve seen.

W/the level of tune required for a DI 2 stroke to pass the sniffer tests, they are so lean, and close to melt down, if they even hick up (water in fuel, too much wheel, basser abuse) I wouldn’t expect one to live.

On the big E-Tec’s on the (highly strung) bassers, it looks like 2 - 300 hrs of life is common.
(similar or a bit more than the Opti’s)

In a lesser stressed environment, I’m seeing/hearing 5 - 10 times that.

Just read of an owner winterizing his 225 e-etc (I think in Fla) and it had 1700 hrs and was orig
and have seen many for sale with 2000 hrs +.