8v71TI Performance

[JCG]

OK major problem is fixed but now I need to fine tune.

The boat is 1979 Hatteras Sportsfisher, twin 871TI detroits, with a full load of fuel, fairly clean bottom and freshly scrapped props, @ 1800 rpms gps indicates 15-16 knots @ 2100 WOT speed indicated is about 20 knots..no smoke..... does all this sound like I am getting about all I can really expect out of these engines?

 

[bigbill]

those 8v71ti's should turn 2350 rpm's at wot. you may have too much prop. rev your engine up in neutral and see what they turn, the govenor should let them turn about 2450rpm's to 2550 with no load. if they do then you probably have too much pitch in your props. bigbill

 

[REBrueckner]

My 1972 48 YF 8V71TI's turn about 2150 RPM WOT and deliver about 20 knots at that RPM. Seems close to your results. Original Hatteras records show she did 22.2 knots when new. I swing 28 x 32 four bladed props according to the stamps on the props.

Since I never run anywhere near that RPM, usually cruising about 1400 to 1500 RPM and about 10 or 11 knots, I have left the boat "overpropped" to help boost load a bit at my modest cruise RPM.

If you want to run hard, run fast, you might get another two knots or so at WOT by following bigbills advice. Since the engines appear overpropped a bit, I'd run them at a bit lower cruise RPM than normal, say around 1800 RPM. It would be wise to check your turbo exhaust temps at that RPM to be sure the engines are not overloaded.

If you want to gain another two knots or so, you can boost the injector size in your engines...other modifications might alsdo be required.....I posted several years ago here about a 46 Berty with 8V71TI's that gained two knots cruise by boosting HP....likely at the expense of reduced engine life....