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Old 19 January 2004, 13:47   #1
Seb
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Mercruiser

Has anybody had any experience with the 5.7ltr Mercruiser V8 petrol engine? (In terms of fuel consumption and performance)

Cheers,

SEB
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Old 19 January 2004, 14:01   #2
TIM
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WILL GO LIKE HELL,

BUT YOU COULDNT SPILL PETROL OUT A 5 GALLON DRUM AS QUICK AS IT WILL DRINK IT...........
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Old 19 January 2004, 14:19   #3
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Lots of versions from Mercruiser over the last 30 years or so, ranging from 200 - 330hp. The latest fuel injected versions aren't that bad on fuel unless run at WOT. Expect to return similar fuel consumption as a conventional 2 stroke V6 outboard.
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Old 19 January 2004, 14:46   #4
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Ive only had experience with the engine in a ski boat and the Low Wood hotel on Lake Windermere has converted every single one of its Mastercraft all with that engine in them to LPG.

Yes they use the boats a lot but in general they will run 1 boat for about 4 hours a day in peak season and they went to the trouble of having an LPG tank installed on site and all the boats converted to save money on petrol.

While we were filling up in a garage on Windermere we got talkign to a guy with another ski boat with that engine in it and the one statment i remember from the conversation was, "consider yourself lucky, this is the third time ive filled her up today."
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Old 19 January 2004, 14:57   #5
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Ski boat engines like those fitted to Mastercraft or Tige tend to be a higher performance engine than the standard Mercruiser V8. 6ltr Scorpions etc of beefed up 5.7ltrs.

The standard V8's are good solid reliable engines. They have been around for years and are reliable. They do tend to be a bit thirsty, but it is a V8!!

The new MPI is not as thirsty plus you get turn key ignition and the facility to use Smartcraft guages.

I have driven a Bayliner 185 with the V6 MPI engine in it and was doing 55mph with more throttle and trim available (just run out of calm water )

We also look after a Bayliner 205 with the V8 MPI. It is capable of similar speeds (bear in mind it is a much bigger heavier boat).
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Old 19 January 2004, 15:30   #6
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5.7 Litre V8

Hi Seb,

I think this is very likely to be the same as the Volvo 5.7 litre V8. I had one of these for 14 years in a Falcon 23 SPC (hard boat), until this summer. It sounded grrrreat!

If you are thinking second hand, I guess it could well be a carburettor version. If new, it will very likely be fuel injected and rather more fuel-efficient. Mine had a Holley 4 barrel carb and yes - it did drink petrol!

Cruising at around 3600 RPM (30kts) consumption was 2.25nm per gallon. It only became this "efficient" after I changed the power valve, as the "replacement" was of a different spec than the original. Prior to that, I used to get almost exactly 2nm per gallon. That's about 1.10 per minute when cruising, at marina prices!

Today, I would think twice about a large petrol engine, in spite of the question mark over the future price of diesel, as they do seem to go further per mile and at lower revs, so I should think that the life-expectancy of a diesel engine would be much greater. Also, diesels are now much smaller, lighter and quieter than 14 years' ago.

Back to your question ...

In terms of performance, mine was rated as 275hp at the crankshaft and I did have "Duoprop", so - in theory - I probably gained another 10% more power. Of course, every boat will perform differently but mine used to do just over 36kts flat out ("WOT") at just over 4400 RPM.

I hope this helps!

Regards,

Chris.
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Old 19 January 2004, 15:43   #7
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i had 5.7 350 magnum engine in ski boat,engine was a 1998 fuel injection and started first turn every time,never had any problems apart from fuel consumption,about 16 gallons per hour at wot.
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Old 20 January 2004, 07:35   #8
Seb
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Thanks very much for the feedback guys...i realised that it would be expensive to run but, the type of mpg that your talking about is scary!!

Maybe ill go down the diesel conversion route or, just steer well clear!

Cheers

SEB
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Old 20 January 2004, 12:28   #9
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The 5.7 V8's (Volvo, Mercruiser) are based on the chevrolet small block. This is the most common engine in the world, so spares are very cheap by comparison. Obviously you get what you pay for, but for most leisure use (ie not huge numbers of hours), you'd have to burn a lot of diesel to offset the additional cost of the engine. Also, on carbureted engines, it's well worth working out when the 2nd choke opens. Fuel consumption is better until the 2nd chokes open, at which point a team of dwarves climb on top of the engine and start pouring petrol in by the bucketful.
I've got 2x7.4's (Which are Big Block Chevy's) and I plan towing an oil refinery with me.
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