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350 verado verse new 400m

Old 05-21-2019, 06:39 PM
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Default 350 verado verse new 400m

Anyone repower their boat from 350 verado to the new 400m (non-racing)? Wondering if the $7k premium for a pair is worthwhile or not. I havenít seen any numbers comparing these two. Would be interested in anything running twins.
Old 05-21-2019, 07:11 PM
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Me too!
Old 05-21-2019, 07:44 PM
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They run every bit as strong in the midrange as the 350, better hole shot, touch better midrange fuel economy and 3-4 mph up top depending on the application.
Old 05-21-2019, 09:26 PM
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Originally Posted by sundancekid View Post
They run every bit as strong in the midrange as the 350, better hole shot, touch better midrange fuel economy and 3-4 mph up top depending on the application.
Now I am confused, pretty sure I read that the 400 and 350 were pretty much the same except the 400 revs higher. Better hole shot and midrange?
I know the redline is higher on the 400, something does not sound right.
Old 05-21-2019, 09:28 PM
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Just repowerd my 34 yellowfin with twin 400 Verados.

3 men on board w/ 270 gal of fuel
Rev 21's

10 seconds to plane

38.8MPH at 3800 1.54 MPG
41.5MPH at 4300rpm 1.71MPG
59.1 MPH at 6300 .88 MPG(WOT)
Old 05-22-2019, 04:38 AM
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Originally Posted by Mrhavasu View Post
Now I am confused, pretty sure I read that the 400 and 350 were pretty much the same except the 400 revs higher. Better hole shot and midrange?
I know the redline is higher on the 400, something does not sound right.
This is where you went wrong. Reading and experiencing are two different things. sundancekid’s assessment is spot on and right along with what we have seen as well. The 400M’s programming was designed in order to provide some fuel economy gains, increased low end and midrange torque. Of course, with increased RPMs, increased top end speeds will occur.
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Old 05-22-2019, 06:58 AM
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Originally Posted by sundancekid View Post
They run every bit as strong in the midrange as the 350, better hole shot, touch better midrange fuel economy and 3-4 mph up top depending on the application.
Iím thinking better hole shot because itís spinning a lower pitched prop, to gain the increased WOT RPM?
Old 05-22-2019, 07:05 AM
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Originally Posted by davidwademarine View Post


This is where you went wrong. Reading and experiencing are two different things. sundancekidís assessment is spot on and right along with what we have seen as well. The 400Mís programming was designed in order to provide some fuel economy gains, increased low end and midrange torque. Of course, with increased RPMs, increased top end speeds will occur.
If it is programming differences, could they possibly reprogram a 350 to get the same performance gains out of it minus the top end?
Old 05-22-2019, 07:09 AM
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Originally Posted by SaltyRhino View Post
If it is programming differences, could they possibly reprogram a 350 to get the same performance gains out of it minus the top end?
I assume this is the type of tuning USP Marine does, gets similar results but voids the warranty...
Old 05-22-2019, 07:24 AM
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You can def program them and make them faster but not interested in voiding the warranty on a new engine. Looking at the performance bulletin on a quad 37 Freeman. They gained 4-6 MPH top end and slightly (negligible) mpg on mid range cruise. 79 wot on the 400m and 73/75 depending on conditions/props with the 350s.

so thatís quads with twins Iíd say 2-3mph top end. Probably not worth the $7k for me and most.
Old 05-22-2019, 07:27 AM
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The 400M came out the week I picked up my boat or I would have upgraded. I called Mercury and asked if I could tune my engine (350) to make it the same and they said absolutely not.
Old 05-22-2019, 08:02 AM
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Originally Posted by avid lurker View Post
Just repowerd my 34 yellowfin with twin 400 Verados.

3 men on board w/ 270 gal of fuel
Rev 21's

10 seconds to plane

38.8MPH at 3800 1.54 MPG
41.5MPH at 4300rpm 1.71MPG
59.1 MPH at 6300 .88 MPG(WOT)
I sold a YF34 last year that I'd run for 7 years with twin F350s. My mph numbers were just about identical to this, but my fuel efficiency was not quite this good. With the load described I would have been more like 1.5mpg at 4300 rpm doing low-mid 40s mph. Once I got her up to 50mph (around 5K RPMSs give/take), I was always right around 1 mpg, perhaps with a bit heavier load than your test, so maybe 1.1 with your load. At WOT (5700-5800 with the F350s), I'd be right around your WOT numbers: 58-ish mph .8 mpg.
Old 05-22-2019, 08:11 AM
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Originally Posted by Mrhavasu View Post
Now I am confused, pretty sure I read that the 400 and 350 were pretty much the same except the 400 revs higher. Better hole shot and midrange?
I know the redline is higher on the 400, something does not sound right.
Exactly, they are the same engine the 400 just makes the extra 50hp at top end.
Old 05-22-2019, 09:07 AM
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Originally Posted by avid lurker View Post
Just repowerd my 34 yellowfin with twin 400 Verados.

3 men on board w/ 270 gal of fuel
Rev 21's

10 seconds to plane

38.8MPH at 3800 1.54 MPG
41.5MPH at 4300rpm 1.71MPG
59.1 MPH at 6300 .88 MPG(WOT)
You are over propped, get the RPMs to 6800 and you will pickup some fuel economy and top speed.

You gain hole shot because you have more HP and another 400 RPMs to play with, so your prop pitch stays the same. Same thing with mid range economy, less load on the engine due to running the same pitch at partial throttle, so no added fuel burn.
Old 05-22-2019, 10:28 AM
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Originally Posted by ucf_motorcycle View Post
You can def program them and make them faster but not interested in voiding the warranty on a new engine. Looking at the performance bulletin on a quad 37 Freeman. They gained 4-6 MPH top end and slightly (negligible) mpg on mid range cruise. 79 wot on the 400m and 73/75 depending on conditions/props with the 350s.

so that’s quads with twins I’d say 2-3mph top end. Probably not worth the $7k for me and most.
they lowballed the performance report on that freeman....it hit 83. But now with radar and outriggers and second station and some weight, 79 is now accurate.
Old 05-22-2019, 01:20 PM
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Originally Posted by sundancekid View Post
You are over propped, get the RPMs to 6800 and you will pickup some fuel economy and top speed.

You gain hole shot because you have more HP and another 400 RPMs to play with, so your prop pitch stays the same. Same thing with mid range economy, less load on the engine due to running the same pitch at partial throttle, so no added fuel burn.

I have a set of Eco 19ís that I should be able to try out this weekend. Iím trying to get the best mpg at cruise with a heavy load for those long canyon runs
Old 05-23-2019, 04:59 AM
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Originally Posted by SaltyRhino View Post
If it is programming differences, could they possibly reprogram a 350 to get the same performance gains out of it minus the top end?
Interesting point. I’ll bring this up to someone ‘in the know’ and report back.

Originally Posted by VaporTrail1 View Post
The 400M came out the week I picked up my boat or I would have upgraded. I called Mercury and asked if I could tune my engine (350) to make it the same and they said absolutely not.
It can be done, but you have to have a VERY good relationship with Mercury. Beyond even our relationship with them.

Originally Posted by Rod27 View Post
they lowballed the performance report on that freeman....it hit 83. But now with radar and outriggers and second station and some weight, 79 is now accurate.
And just how would you know that Rod? If anyone wants a direct comparison of the 350 to 400M, you’re definitely one here on THT who has that in real world info.

BTW everyone, for a 400M to 400R comparison, a quad 400R Freeman 37vh also tops out at 83mph.
Old 05-23-2019, 06:29 AM
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Originally Posted by avid lurker View Post



I have a set of Eco 19ís that I should be able to try out this weekend. Iím trying to get the best mpg at cruise with a heavy load for those long canyon runs
Ran those on a 34 with twin 350s and they were excellent, easy cruise 40 at 1.7 MPG and 60 up top. Gave some much needed bow lift to that hull, I think that made a world of difference, especially in the midrange.

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