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47' Wellcraft Excalibur downgrade to 496 Mag 375 hp

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Old 03-01-2011, 11:07 AM
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Default 47' Wellcraft Excalibur downgrade to 496 Mag 375 hp

I need to replace an engine in a 2003 Wellcraft 47' Excalibur. I would prefer to replace both at the same time. I know the boat was offered with the 375hp option. I know the the 425hp 496 mag ho's the boat currently has make up their differnce in top end. My questions are as follows..

1. Would I have to reprop if I install the 375hp versions?
2. Will the 375hp versions perform better out of the hole and at the 3500 rpm range that I spend most of my time?
3. Top Speed will be reduced for 51 mph to...?
4. Or just upgrade them back to the 496 mag ho specs with the ECU's that I already have and cam that is slightly more radical then the stock 496 mag ho cam?

Regards,

Travis (almost first time poster)
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Old 03-01-2011, 12:16 PM
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That's a big heavy boat to be downgrading power on and the 50 hp per engine decrease will affect both cruise/speeds and top end as well as acceleration. Stay with the higher horsepower and torque of the 425Hp version. My suggestion would be to use the ECM's you already have as buying used or new ones or having the old ones re-programmed is moderate to expensive and cams are not that expensive other than the replacement cost.
We have good cams in stock that are actually better performing than the GM stock HO camshaft. Call us @ (866)496-8181 if you are interested in that option.

Best Regards,
Ray @ Raylar
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Old 03-01-2011, 12:33 PM
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I own the same boat,, i took the 496HO motors and completely rebuilt them internally all forged parts, head work and changed the computers to MEFI4B's and put 2.3 whipples on them ,,, motors dynoed at 700hp and 800lbs trq,, i rebuilt the bravo3 drives by adding a tower from max machine worx, billet top cap, XR gears, torington bearings and two drive showers,, one for the cap and a halo one for the case.. i run a 28 prop that bblades worked on... boat runs 61-62 mph on gps and cruises at 45 all day long... with full fuel and people,,,,, ive had this set up for 6yrs now and currently building bigger motors 1000hp ish and putting arneson 7M surface drives on the boat...the old motors and drives are for sale if your interested 65hrs on the motors since rebuild and about 30 hrs on the drives,,, the boat runs amazing at 60 ... let me know if you have any questions ...id be happy to help
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Old 03-01-2011, 12:44 PM
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I have drive a few M470 Riviera's with diesels and Bravo 3's. I would think this is the best package for the boat. If you are going to keep the boat for a while and want the best cruise and fuel economy it may be worth looking into.
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Old 03-01-2011, 01:04 PM
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If done right the 496's are fine and will go 300hrs without a major overhaul.... diesels will only slow the boat down and its not worth the cost vs improving the 496's....fuel wise its about the same.... the hull on this boat isnt a typical express cruiser hull ,, its a streched out scarab hull that wants to run on top of the waves and not be at max load and push through them.... boat needs more power
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Old 03-01-2011, 01:09 PM
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Quote:
Originally Posted by zemaestro View Post
I need to replace an engine in a 2003 Wellcraft 47' Excalibur. I would prefer to replace both at the same time. I know the boat was offered with the 375hp option. I know the the 425hp 496 mag ho's the boat currently has make up their differnce in top end. My questions are as follows..

1. Would I have to reprop if I install the 375hp versions?
2. Will the 375hp versions perform better out of the hole and at the 3500 rpm range that I spend most of my time?
3. Top Speed will be reduced for 51 mph to...?
4. Or just upgrade them back to the 496 mag ho specs with the ECU's that I already have and cam that is slightly more radical then the stock 496 mag ho cam?

Regards,

Travis (almost first time poster)
1) If you want to get the most out of everything, rework the props at a min.
2) Probably not.
3) 47-48 mph would be my guess.
4) I'd give Ray a call on this one.
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Old 03-03-2011, 10:25 AM
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ZEMAESTRO are you buying this boat?

http://www.boats.com/boat-details/We...ibur/117739041

needs alittle tlc but should clean up nice
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Old 03-03-2011, 11:12 AM
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Quote:
Originally Posted by zemaestro View Post
I need to replace an engine in a 2003 Wellcraft 47' Excalibur. I would prefer to replace both at the same time. I know the boat was offered with the 375hp option. I know the the 425hp 496 mag ho's the boat currently has make up their differnce in top end. My questions are as follows..

1. Would I have to reprop if I install the 375hp versions?
2. Will the 375hp versions perform better out of the hole and at the 3500 rpm range that I spend most of my time?
3. Top Speed will be reduced for 51 mph to...?
4. Or just upgrade them back to the 496 mag ho specs with the ECU's that I already have and cam that is slightly more radical then the stock 496 mag ho cam?

Regards,

Travis (almost first time poster)
I sure would not take a step down on power. Raylar Engine has several excellent naturally aspirated upgrades to at least 600hp. That's the way to go IMO.
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Old 03-03-2011, 06:08 PM
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I had a friend w/496 HO's in his and , he got 1100 hours with only minor repairs . Sold them as running take outs before they broke and started over with another set .
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Old 03-04-2011, 06:14 PM
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Thanks for the replys. I'm moving up from a 1989 Suckcraft 310sc. The boat gets no respect, unless somone recognizes that it is in fact a Tiara. I have just about gotten it to where I want it mechanically. Twin 260hp small blocks propel it just fine, most I have had aboard was 9 and it ran out great, flat and level, faster then anyone else I cruise the bay with. Your responses are in line with my gut instincts. I had posted on a diesel forum about using a modified 12v cummins. I have a few friends with some serious 5.9's (I drive a 24v common rail) and like everyone else has in the past, I had to ask why no one has put a reliable 500-600hp 5.9 for marine applications. Well the biggest issue is heat...I would like to try a pair of konrad's and converted 5.9's. Basically a dream I guess, as I'm too busy to take on that project myself right now. However, it is not beyond the scope of my capabilities.

Ray...I have read SEVERAL of your posts and want to thankyou for being who you are, I most likely will purchase atleast a set of cams from you...I'm guessing 103's with a set of springs.

47ex, I had thought about taking your path, but it is an uphill battle and I don't want to fight the hull. I tend to get carried away on projects, and I would like to keep this one simple. Also, I have been in, and crawled around the 400ss's and the Wellcraft/Riveria in my opinion is a better boat, period. Yes, that is the boat, and yes it needs a ton of TLC

SS930, The props are also on the agenda
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