1987 41' Cruise speed & engine life?

[Timeless56]

Gentlemen:

What is the cruise speed at 2000 rpm of a 465hp-671 on a 1987 41' SF. Also engine life??? engines have 2000 hrs?? and GPH at cruise???

Kind of Blue

 

[Passages]

My results should be somewhat close.

42'C w/671ti pumped to 410 hp.

2000 rpm is about 18 knots. But I had the prop pitch reduced to prolong engine life. WOT of 2550 gives about 25-26 knts.

I cruise at 2100-2150 and get 20-21 knts and burn 29 gph.

Add a knot or 2 for your speed plus a gallon or 3 for fuel burn.

Regarding engine life, hard to say. Mine are still going strong after 27 years and 1400 (original) hours. A lot depends on how the boat was used (or abused) You might get another 500 hours. If this is a prepurchase assessment, perform the "Genesis 30 Second Engine Test" located in the FAQ section. Then pull the air box cover plate and inspect the wear on the cross hatches. These 2 checks should give a good sense of engine condition.

 

[CMP]

Engine life in the hopped-up 71-series is an interesting deal. I had a pair of 4-71's, aftercooled and turbo'd which I rebuilt. After rebuild, I had 2,000 ish hours on them and they were ready to blow. The guy who bought my boat had it a year and he replaced them. Every 71-series owner I know has had major issues after 2,000 hrs and I think we ask alot of an engine wen you pump it up that hard...

CMP

 

[REBrueckner]

Engine life on the high HP/cube Detroits is highly dependent on cruise RPM. At 1 HP/cube or more, you are beginning to strain the engines around 2000 RPM and higher. The usual 80% of top RPM for a diesel cruise, or around 2000 RPM for these engines, is a bit too much for long life. At 1800 or 1900 RPM you'll be able to extend life a lot, 25% likely even more. No reason not run run them at 2200 for an hour or two to escape bad weather, but day in day out, it does take a toll.

 

[Timeless56]

I really appreciate this feedback guys!