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Star92
04-17-2005, 11:57 PM
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.

rem_pss308
04-18-2005, 12:03 AM
The 240 HP is a standard 351 ford. the 285 HP is a 351 ford with GT-40 heads.

babymoore3
04-27-2005, 12:07 AM
Are the GT-40 Heads just I/E port sizing or polishing or ?????

Thanks!
:steering:

G-man
04-27-2005, 10:25 AM
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.

east tx skier
04-27-2005, 11:07 AM
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.

Hunterb
04-27-2005, 02:43 PM
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

east tx skier
04-27-2005, 03:16 PM
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.

Hunterb
04-27-2005, 04:24 PM
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 :rolleyes:

east tx skier
04-27-2005, 04:38 PM
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. :woohoo: