bertram31.com

any idea of cruising speed, top end, with these in a 31
used pair in south florida with gears for with 800 original hours that I am looking at

If those are 6bta's with 1.5:1 trannies, properly propped to a normal weight 31 you should cruise @ about 24 knots/2400 rpm and wot @ 28/2650 rpm

Matched pair of 5.9 turbo 250 hp, complete with twindisc 502 angles,exhaust and motor mounts low hours ready for your boat

Same motors I have, the 250s. Get the CPL # from them. If the aftercoolers look like tombstones on top of the motors they are probably the CPL 1247s, same as mine and pretty much the bullet proof of all bullet proofs of all 6BTAs since the aftercooler is fresh water cooled vs. seawater and requires about zero maintaince.

About the only test on them that would be meaningful would be a blow-by test to see if the rings are shot -otherwise there ain't a whole lot to 'em. The will show very low oil pressure at idle when hot but that's normal.

Check 'em good for exterior rust as more 6BTAs have died from neglect that running.

Ditto Walt on the speed - I run 1.53 gears and 21 x 22 three blade nibrals and speed and rpm are linear from about 1800 up - 2000 rpm equals 20 kts, 2400 equals 24 kts, and WOT is 2650.

Best motors I've ever owned by far.

UV

I get a little higher top end, clean botom I can get 29knotsand change at 2750rpm.
Ditto on cruise at 24knots

Michael-If you can hit 2750 you can add an inch of pitch on your prop. If it were mine, I'd add cup rather than pitch so as to not add any speed on my low end (idling, trolling, docking), but would definitely give you a knot or two more at cruise.

4 blade 18x22 was the best set of props I had on my comparable horsepower Volvo Tamd 60Bs -- with a little cup. Got me an easy 24 knot cruise at 2350, but more importantly, made dock manuevering a dream - I could walk that boat in any direction inch by inch with those big 4 blades at very slow speed!

I've got 250s with 4blade 21/23 little cup. Numbers about the same 2650 max give 29kts. Usually cruise offshore at 2000---20-21 kts, 2400 gives more towards 25' the money comes when it gets rough and I can cruise at 1600 and 17 kts. Great way to cover ground in the short chop we get here in s fla. Great, I say great motors.

Spencer,

I hope it works out for you. These seem to be the go to motors in our boats. This is probably the route I am going to have to at some point. Please keep us posted.

Spencer

Just for comparison purposes, I have the 270 remans which is the same engine as the 250. Difference I believe is in the fuel pump. The Bosch pump ups the HP slightly. I am running light, no tower or hard top. At 2200 I am clicking along at an easy 24 knots. Top end turning 2650 I hit 29.7. I a turning a 20x23 prop with cup.

Fuel use, real stingy compared to the old big blocks. I don't have a flow meter, but I am burning about than 15 gallons an hour at cruise.

tony it is not even close to the 250 hp of yesteryear ,not that the 250 was bad. the 270 remax is completely up graded except crankshaft .cylinder heads ,pistons, exhaust manifold and bosch injection pump,injectors not even close.even add on like alternator, starter motor, raw water pump,turbo totally differant . look at your alternater and post the output here--------surprise!!!

Correction 20/23 4 blades not 21

To the faithful
Thanks for all the information
Will try to take some pics and post