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medicmoose
12-01-2009, 05:00 PM
So my boat has the 6.0 Indmar and according to the Indmar site and according to the Mastercraft website it is a 400 hp motor. I was looking at my insurance papers and noticed that according to the insurance provider the boat was a 350 HP boat. So I thought I better double check...I looked at the Certificate of Origin from MC and it too is listing my boat as 350 HP.

When I checked with MC about the discrepancy they stated, "once they're put in the boat you have to factor in the muffler restriction that has been added to it".

So do I understand it correctly that the addition of mufflers reduces the HP rating of these motors by 50?? :confused: So the 350 is really a 300 and the 310 a mere 260??? A 50 HP drop just from the mufflers sounds a little suspect and if this is the case....I would call this false advertising...unless of course they advocate and give you the option of running without a muffler. :rolleyes:

xstarplease
12-01-2009, 06:03 PM
IMHO, I think 50 hp for mufflers is a bit on the high side, but it is entirely possible. I would think MC would be able to design a more efficient muffler if the current mufflers are that restrictive: however, I'm guessing that "400hp" motor can do the job with ease. Horsepower is just a mathematical formula anyway... How much torque does it make?

MYMC
12-01-2009, 06:39 PM
So my boat has the 6.0 Indmar and according to the Indmar site and according to the Mastercraft website it is a 400 hp motor. I was looking at my insurance papers and noticed that according to the insurance provider the boat was a 350 HP boat. So I thought I better double check...I looked at the Certificate of Origin from MC and it too is listing my boat as 350 HP.

When I checked with MC about the discrepancy they stated, "once they're put in the boat you have to factor in the muffler restriction that has been added to it".

So do I understand it correctly that the addition of mufflers reduces the HP rating of these motors by 50?? :confused: So the 350 is really a 300 and the 310 a mere 260??? A 50 HP drop just from the mufflers sounds a little suspect and if this is the case....I would call this false advertising...unless of course they advocate and give you the option of running without a muffler. :rolleyes:

I don't know who you spoke with but the answer while in the ballpark is simply not the entire story.

The engines are rated by Indmar on a dyno which represents the best possible conditions...measured fresh air, large room for heat dissipation, no mufflers or "dyno" mufflers, no water in the exhaust, no accessories, etc and so on. The dynamometer measures torque (among other things) and calculates HP based on those readings. Many factors contribute to this reading including the test performed...it could be a 200 rpm step test, 200 acceleration run etc. Every engine manufacturer uses the best numbers to publish...obviously for sales/PR reasons. Almost forgot...Add to this the dyno corrects all readings using a "correction factor" based on altitude and weather so that data can be compared regardless of time of year and location.

When installed in the boat the engine is confined to a very small space contributing to heat soak. Further the engine gets to breath all that hot air as there is no clear way to bring cool air under the engine box. Also the exhaust gets to fight with water for access to the exits and then there are the mufflers (and cats depending on year) and baffles knocking the water/exhaust mix all around. Add to this the drag from the raw water pump, circulation pump and alternator and you get the picture...and oh ya...you get what she makes, there is no "correction factor". If it is hot and humid and you are in Denver you are gonna notice...take it to the inter-coastal on a 30 degree day with no humidity and you'll have a different engine altogether.

BTW, I just checked all of our 2009 and 2010 inventory MSO's and they all state 400hp for the LY6

medicmoose
12-01-2009, 07:04 PM
Well, I can't argue with that! Thanks for the detailed insight...I appreciate it!

jipster43
12-01-2009, 08:19 PM
It's never humid in Denver.

JP :)