ratman

why do mers motors make so much more hp and torque than jc's motors at a lot lower rpm? the motors seem very similar. 4.375 stroke, roots blowers, dual carbs. won't the lower rpm motors last a lot longer than ones you have to ring crap out of to make hp? do you have to run a 2 speed trans to get a boat on plane with peaky high rpm motors, or is it better to get everyone to move to the front of the boat until it gets on plane? what is considered cruise rpms for jc's motor package 5600 rpms? is it easier on drives if the motors don't make power down low in the rpm range? just wondering what gives

JCPERF

I was wondering this myself.The effiency of the 14-71 is better than the 8-71 i ran.

ratman

tommy @ chief told me he makes more hp with a 1071 than a 1471 cuz you watse hp turning the bigger blower, and can make all the boost you need with a 1071.
JC, why did you only run a 871 on this combo? have the motors been put in the boat yet? does it get on plane ok? what torque do the motors make @ 2500 rpm?

ratman

jc can you swap the blowers and make a pull with a 1471?

JCPERF

I wanted to use bigger blowers but thats what we had.I ran these motors last year in a 37 OL.Ran 119 GPS.goes right up on plane.Dyno wont hold motor as low as 2500.It makes peak torque @4000.

JCPERF

I wanted to test that but you should run Dominators so there is less restriction.

vette131

i think it's more about the camshaft selection than the blowers. an 871 is going to run out of steam before a 1471.
mer's peaked below 6000 jc's are just begining to make power at 6000. mer's cam better matches the power curve of the engine especially for a marine aplication.

JCPERF

I also have chevy style heads,not Profilers.

RumRunner

This is a ton of the reasoning!!! The RFE heads flow a ton more, and atomize the fuel much better than a conventional GM head.

Bottom line, it's not a fair comparison to go between these two packages. Both engine builders did very good jobs given the parameters they had to work within. I would bet that if they were both given the same budget, baseline of parts, and tested at the same facility the results would be very close. Both guys do a very good job. It's just a matter of getting what you need for your combination. JC may have moved the powerband up a little to save the outdrives for the customer?

ratman

i was always under the impression that big high flowing heads make power up high...where in this instance the big high flowing heads are make power at a lower rpm. i am not looking at total hp but where its being made, i just don't understand why a boater would want to twist a motor that hard to make power, i just cant see any benefit in reving almost 7 grand from a longevity stand point.