Sister Motors

Freakwater · 02-27-2006, 09:59 AM

What is the deal with motors that have the same displacement and different HPs? For example the Suzuki DF70 vs. the DF90. Same displacement, same motor weight. Different fuel injection? Different gearing? Are you going to get more life out of one over the other? Better fuel consumption from one over the other?

Thanks,
Freakwater

little doc · 02-27-2006, 03:05 PM

In my limited experience, lower Hp engines with the same block seem to idle better, and are more reliable. The motor tech column in the Oregonian had an article years ago comenting on the life of motors, and they stated that any engine block had x many Hp/hours in it. If the engine was tweaked to give more muscle, it wouldn't last as long. If you look at big boats like Nordhavn, which is a dedicated long range trawler, they take motors and detune them to lower than standard Hp ratings with the expectation that they will be able to run longer with less maintenance (so I am told, I don't own one). Maybe someone else has more defintive knowledge about the subject, but thats my 2 cents.

jimh · 02-27-2006, 04:48 PM

I think it would be also that there are requirements for certain HP for boats. Instead of tooling up different motors they just change the fuel system. Presto, new motor with different HP rating.

tomictime · 02-27-2006, 06:06 PM

in general for O/B anyway it is carb and some advance for a slight shift upwards in power curve, slightly higher WOT and HP peak. I had a 175 V6 OMC built on the 200 block, strong engine. Most 175 (not all) are wrung out 150's.

As to BIG engines, they rate those on duty cycle, so yes you can get more out of a detuned engine.