Repower I/O Qs.

[randlemanboater]

Originally Posted by Hammerhead

Wrench ( highly respected shop) found a rebuilt longblock for 1500.oo and will do all the labor for another grand. That's alot cheaper than I tho't it'd cost.
I should have it back in a week or so. ThanX guys.

Put it in yourself and save a grand.

[garagenc]

I'm doing the whole thing myself, I pulled my old 305 and am buying a 350 from Rapido marine and installing myself. They use car blocks versus a used marine block. $1450 + 150 for shipping.

[THEFERMANATOR]

I bet this one would push a V-20 plenty fast. 5.7L 315HP MAGNUM, would probably at least plane it ;D.

[spareparts]

take a look at this

http://bpi.ebasicpower.com/c/LONGBLO...+Block+Engines
they have your 250( listed as a 4.1 L6) on here for $1599, with a two year warranty

[Hammerhead]

ThanX for the links. I tho't about a 5.7 250hp but, went the cheap route with a rebuilt longblock replacement. Paid 1500.oo for it. Wrench is doin' the install for 1000.oo.

Motor is already out and parts off that need to be transferred to the new motor.

[THEFERMANATOR]

Originally Posted by 76GMC1500

That motor has horrible torque. *220ftlbs at 2600 rpm? *Your oringinal engine made 350 ftlbs peak and would probably have been close to 300 ftlbs by the Cummins 2600 rpm peak rating.

I seriously doubt a 250 straight 6 could develop that kind of torque. The 6.5 diesel V-8 in my SUBURBAN was factory rated at around 380-390 ft lbs of torque, and that's a V-8 diesel. The 255HP 5.7L VORTEC truck motors made 330 ft lbs of peak torque. I would say that 165HP straight 6 probably produces peak torque close to the peak HP number, that's normally a good rule of thumb.

[76GMC1500]

I'm talking crankshaft ratings and I thought he was replacing a 260hp 350 Chevy, those are rated at 350 ftlbs at the crankshaft. Torque is kind of a meaningless number, though. If you ever look at a prop curve, the chart will make no mention of torque. Horsepower is all you need to know.

[spareparts]

horsepower readings alone will get you into trouble, horsepower is the timed application of torque( hp=(torqueXrpm)/5250) you have to know what the rpm the hp is rated at. I've seen a 50 trawler with a single 125 hp engine make 7 knots, it would take two 5.7's to do that in this boat. Saw an model airplane engine that would make 5 hp( at something like 15,000 rpm), but I bet it wouldn't push my lawnmotor as well as my 5hp Briggs. Torque alone won't tell you much either, think of a torque wrench, you're applying torque, but you're not going anywhere. I've started to pay attention to Kw ratings(used on modern engines), I haven't made my self familure enough with them to know what I'm looking at.

[76GMC1500]

kW ratings are identical to horsepower, it's just metric units.

But seriously, if you have 2 engines both turning props at the same speed and are both making the same horsepower, the torque seen at the props is the same, regardless of the torque output of the engine. *If the torque output of one engine was half, it would have to run double the rpm. *In order to spin the prop at the same speed, the transmission reduction ratio would also have to be doubled. *Because the transmission ratio is doubled, the torque output on the prop end is also doubled. *So, the engine that had half the torque at the crank still has the same torque at the prop after going through the reduction gear. *The difference between that 125hp motor and the 5.7L is that the 5.7 would have to be run balls to the wall while the other motor could just chug along.

P.S. I'm trying to be a little controversial to get everybody to think about things. Sure, they're are holes in my logic but there are also points to be made.

[THEFERMANATOR]

Simple way to think of it is torque is how much work an engine can do and horsepower is a measure of how fast an engine can do that work.