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Old 04-17-2005, 11:57 PM
Star92 Star92 is offline
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Difference in Horsepower

I have noticed that mc had two different engines on early 90's indmar carburated engines. Some engines are rated at 240 h.p., and some are rated at 285 h.p.. They basically look like the same engine, a ford 351. What is the difference between the two mechanically. Heads, cam, intake???????? Just wondering.
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Old 04-18-2005, 12:03 AM
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The 240 HP is a standard 351 ford. the 285 HP is a 351 ford with GT-40 heads.
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Old 04-27-2005, 12:07 AM
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Are the GT-40 Heads just I/E port sizing or polishing or ?????

Thanks!
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Old 04-27-2005, 10:25 AM
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the 285 HO also has a duel feed carb. It gives a little better low end pick up, when it's working. They were a problem child for Indmar. Quite a few people on the board have changed these to the 4160 single feed carb. The same carb as the 240 HP engines.
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Old 04-27-2005, 11:07 AM
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The horsepower difference is the GT40 heads. George is correct about the 4010 carb being on the 285 hp engines. I don't think this has anything to do with the horsepower though (both are 600 c.f.m. if I'm not mistaken). The 4010 is a little more responsive in the hole shot if it hasn't already sputtered and died while you're taking the slack out of the rope. The 4160 carb is preferable in my opinion. After the switch, I was getting more speed at fewer revs with the 4160. The responsiveness of the 4010 versus the 4160 is indistinguishible to the skier. In my experience, only the driver will be able to notice the difference, that difference being the smoother hole shot of the 4160 versus the "right now" response of the 4010.
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Old 04-27-2005, 02:43 PM
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Quote:
Originally Posted by east tx skier
The horsepower difference is the GT40 heads. George is correct about the 4010 carb being on the 285 hp engines. I don't think this has anything to do with the horsepower though (both are 600 c.f.m. if I'm not mistaken). The 4010 is a little more responsive in the hole shot if it hasn't already sputtered and died while you're taking the slack out of the rope. The 4160 carb is preferable in my opinion. After the switch, I was getting more speed at fewer revs with the 4160. The responsiveness of the 4010 versus the 4160 is indistinguishible to the skier. In my experience, only the driver will be able to notice the difference, that difference being the smoother hole shot of the 4160 versus the "right now" response of the 4010.
I can't see any way that the carb has anything to do with more speed at lower RPM's. I think the only way that could happen is with a prop change. Did you make some other changes when you changed the carb? Not flaming you, just curious as I'm almost ready to put my project boat in the water and with the price of fuel right now, I'm interested in efficiencies.

Bruce
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Old 04-27-2005, 03:16 PM
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Bruce, I had changed my prop before I changed my carb, but when I took note of the rev/speed ratio change, the carb was the only variable. The changes were hardly noticeable, but for the digital tach on the perfect pass. For example, 36 mph on the gps was previously 3,475 rpm with the 4010, and afterwards, I was getting 36 mph at 3,425. I don't know the reason. I'd say maybe it was because the 4160 was a new carb, but the 4010 was newly rebuilt when I took these numbers. I know it shouldn't have anything to do with it, but that's what happened and the carb was the only thing that I changed between readings.
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Old 04-27-2005, 04:24 PM
Hunterb Hunterb is offline
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Did you wax it? Tailwind? Going downhill? Was there a tiny chop on the water to break the surface tension? I think there has to be something else happening because, all else being equal, prop revolutions is what determines speed so something has to change with regard to the prop or what it's pushing in order to go faster with less RPM's. I think anyway. I may well be wrong about that. My prop has a big chunk out of it right now (from the PO) so it's in the shop for surgery.

Bruce
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Old 04-27-2005, 04:38 PM
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Bruce, what you're saying makes sense, but those previous numbers were pretty consistent on various ocassions/conditions, so I've ruled out chop and wind. I probably should wax the bottom of the boat, but that was not a variable at the time. Again, what you're saying makes perfect sense, but that's my story and I'm stickin' to it. I got more speed with lower revs after the carb change. I can't think of a single variable that would account for it. The carb was the only change. The amount of gear/people in the boat rarely changes.

As of a couple of months ago, I got a new intake manifold resulting in a slightly lighter boat (yea aluminum) with a bit more torque and horsepower, so no further experiments are possible.

/throws down smoke bomb and runs away laughing.
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To me, this forum is about love of inboard boats. It is about the sharing of information and, on a good day, some humor. It is not about post count, brand of boat, or any other superfluous labels that lend themselves to a false sense of superiority. Please, respect one another, try to pass on accurate information, and keep your eye on the ball.

Last edited by east tx skier; 04-27-2005 at 04:41 PM.
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