Yamaha V8 425-HP 5.6-liter Direct-injection Engine

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jimh
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Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Tue May 22, 2018 8:23 am

Yamaha will soon--in a few hours--introduce a new V8 outboard engine with 425-HP. Their website has been teasing this new engine announcement for several days. As soon as Yamaha makes their formal introduction, we'll get the details of this new model, said to have a direct-injection 5.6-liter displacement and weigh 999-lbs in certain configurations. No mention of a price, but it could easily be $35,000 or more.

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Tue May 22, 2018 10:35 pm

The website at Yamaha finally changed and is filled with information on the new 425-HP V8 5.6-liter direct-injection engine. The best introduction to this new engine is watching this video:

https://www.youtube.com/watch?v=fpi4MAYkyCY

This new 425-HP V8 outboard is really a clean-sheet design, differing in many ways from all prior Yamaha models. I don't think it has any application to legacy Boston Whaler boats, but it is certain to be popular in the new mega-center-console 40-foot category.

There is only one performance report listed:

https://yamahaoutboards.com/en-us/home/ ... 425_5-9-18

Triple 435-HP engines on a 39-foot center console, that hits 72.7-MPH with 0.64-MPG, burning 113.8-GPH. Those numbers are just out of the realm of anything I can imagine. The technology is interesting, but the weight (and cost) are probably too much for any application on a older Boston Whaler boat.

Don SSDD
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby Don SSDD » Wed May 23, 2018 7:09 am

At 999-lbs per engine and with three engines, how much weight for a full tank of fuel for this setup?
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Wed May 23, 2018 9:06 am

In the test report, the "weight as tested" is over 16,000-lbs. With the engines burning 113.8-gallons per hour, the boat weight decreases by about 711-lbs every hour. Fuel capacity is 616 gallons.

If the engines are throttled back to 3500-RPM, the boat runs 36.6-MPH at a cruise economy of 0.98-MPG. That gives it a range of about 600-miles.

What is most crazy: even at idle speed, 1000-RPM, the boat only gets 1.15-MPG.

msirof2001
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby msirof2001 » Wed May 23, 2018 12:55 pm

Would be interesting to put one of these on a 1993-1997 OUTRAGE 24. Max HP rating is 400, this is 425. Orange County, CA Sheriff in Newport Harbor has the commercial version of the OUTRAGE 24 with twin Yamaha F200XB engines. The F200XB is over 480lbs. Twin F200 XBs is not far from the weight of the new Yamaha 425. Not sure if the transom is strong enough for all that power on one set of bolts. The other point would be to figure out the intersection of the number of days you can take a 24 footer to well over 50mph on the ocean with the days you're able to go out on the boat to see if it is really worth it or not. But that one day would be priceless.
Current: 2017 Everglades 295cc, Previous1: 1995 Boston Whaler Outrage 21, Previous2: 1974 Sevylor Caravelle 3-man liferaft.

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Wed May 23, 2018 1:25 pm

'2001--that is an interesting idea: replacing twin 200 or twin 225 with a single 425. Many years ago I noted that with the introduction of 300-HP outboards, the use of twin 150-HP engine would probably decline. Maybe this 425-HP V8 will find a home on transoms that used to run twin 200-HP.

I think the engine mount on these 950-lbs outboards won't be the standard BIA mount from the 1970. The mount is mentioned as being a new design, and I suspect it uses wider mounting hole spacing.

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Wed May 23, 2018 1:38 pm

There are several more performance reports posted today. Here's the biggest boat-engine rig:

https://yamahaoutboards.com/en-us/home/ ... 8-2018_occ

Four 425-HP--about 4,000-lbs of outboards--on the transom of a Grady-White 45-footer. That boat tops out at 58-MPH, which is quite respectable considering the test weight was 35,454-lbs.

Hmm, let's do some math: 425 x 4 = 1700-HP. That is a LBS/HP ratio of 35454/1700 = 20.8-lbs/1-HP.

My Boston Whaler REVENGE 22 W-T Whaler Drive weighs about 4200-lbs and has 225-HP. LBS/HP = 4200/225 = 18.LBS/HP. But I can only hit about 42-MPH top speed. That Grady-White hull must be darn efficient. Its Crouch's hull factor works out to 265--very high speed hull. My classic Boston Whaler hull works out to a Crouch's hull factor of 181, typical for those hulls.

At full throttle the big Grady-White is getting 0.4-MPG. Or in a different analysis 2.5-gallons of fuel to go one mile. Or 2112-feet per gallon. Or one pint of gasoline moves the boat 264-feet. Egad, that is a lot of fuel flowing into those engines and coming out as exhaust emissions.

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Fri May 25, 2018 9:58 am

My price estimate was off. The MSRP of these new 425-HP engines ranges from about $45,00 to $47,000 depending on shaft length and standard or counter rotation. So that's about $90,000 for twins, $135,000 for triple, and $180,000 for four as used on the big 45-foot Grady-White.

jimh
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Re: Yamaha V8 425-HP 5.6-liter Direct-injection Engine

Postby jimh » Sat May 26, 2018 6:17 am

Another significant difference in the new 5.6-liter V8: it can turn a 17-inch diameter propeller.