Sunseeker Apache 45 Diesel repower

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Apache45

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I have a Sunseeker Apache 45 presently running 2 X Mercruiser 7.4L Bravo engines rated at 300hp each coupled to Bravo 2 sterndrives. I would appreciate advise as to what would be the recommended diesel engines whilst keeping the existing drives. I've been offered Cummins VT8-370M which I think are way too large and heavy. Also Isotta Fraschini ID32SS6LM rated @375hp.

I look forward to all your views and comments.
 
Are you doing the conversion yourself, or paying an engineer to do it??

Neither of those motors are suitable for a Bravo 2. Obvious choice for me would be either something from the Mercruiser diesel range, or a Yanmar 315hp. Either of these would work with a Bravo, might need to re ratio them though.

All the Apaches I've seen have been triples, so I assume you're not too concerned on performance, although a pair of Yanmars would be quicker than your current set up.
 
Why do you want to keep the same drives. Ratios will probably be wrong going from petrol to diesel.

I know of 2 Apache 45s with Volvo D6 and DPH drives. They go well with this combination.
 
Not sure the Bravo 2's will be man enough for the job, I ran a Yanmar 315 in a previous boat through a Bravo 3 and was advised to fit a drive shower (spray onto top of drive) to keep the top end cool on extended high speed trips, heard a few stories of Bravo 3 drives shredded by this motor without the shower fitted.
 
RobWales said:
Not sure the Bravo 2's will be man enough for the job, I ran a Yanmar 315 in a previous boat through a Bravo 3 and was advised to fit a drive shower (spray onto top of drive) to keep the top end cool on extended high speed trips, heard a few stories of Bravo 3 drives shredded by this motor without the shower fitted.
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Bravo 2 anctually more robust than Bravo 3
 
piston said:
Are you doing the conversion yourself, or paying an engineer to do it??

Neither of those motors are suitable for a Bravo 2. Obvious choice for me would be either something from the Mercruiser diesel range, or a Yanmar 315hp. Either of these would work with a Bravo, might need to re ratio them though.

All the Apaches I've seen have been triples, so I assume you're not too concerned on performance, although a pair of Yanmars would be quicker than your current set up.
Click to expand...

I'll be doing the conversion myself with assistance. Actually quite a few Apache 45's are fitted with Yanmar 315's unfortunately they're not that readily available on the pre-owned market. I have also been offered a pair of Mercruiser D7.3/270hp which I believe would fit right in.
 
aquatom said:
Why do you want to keep the same drives. Ratios will probably be wrong going from petrol to diesel.

I know of 2 Apache 45s with Volvo D6 and DPH drives. They go well with this combination.
Click to expand...

From the information I have the Bravo 2 drives are good for up to 400hp
 
Apache45 said:
From the information I have the Bravo 2 drives are good for up to 400hp
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They're available from Mercruiser with a 430hp package, but that would be an X drive, (which i suspect yours aren't) and the motors a petrol..

As to them being more robust than a B3, they both use the same top end gearing, just the bottoms differ for obvious reasons.

I've installed about 6 x 315 Yanmars, all but one of them were on Bravo 1's, the odd one was on a bravo 3. Never had any problems with any of the drives, but then they were all in relatively light sports cruisers. Had a few problems with motors though, ripped the side out of one of them, and had a few with electrical problems. (turbo melting the loom)

Being that your 2's are on Petrols, are they 1.5:1 or similar?

I did once buy three Mercruiser Bulldogs (500hp, 8.9 litre) that had been taken out of an Apache, to be replaced by 3 Yanmars. The Mercs were on old school std B1's... I split the packages up, but the drives are still going strong...
 
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Apache45 said:
I have a Sunseeker Apache 45 presently running 2 X Mercruiser 7.4L Bravo engines rated at 300hp each coupled to Bravo 2 sterndrives. I would appreciate advise as to what would be the recommended diesel engines whilst keeping the existing drives. I've been offered Cummins VT8-370M which I think are way too large and heavy. Also Isotta Fraschini ID32SS6LM rated @375hp.

I look forward to all your views and comments.
Click to expand...

Why?
 
If your current setup works, I think I'd be more inclined to sell it and buy a diesel Apache. It'll work out much cheaper than trying to convert your existing.

At least that way you'd be able to sea trial it, where as buying s/h motors is a bit of a gamble. You'll do a couple of grand in parts just on the drives, then you'll need a pair of drive plates, flywheel covers, etc etc, that'll be another couple of grand, probably more. Then you'll need wiring at both dash and engine end, possibly some new instruments, fuel lines, engine mounts, and someones labour. Yard fees soon mount up when your pulling motors.

I've done numerous engine swaps over the years, and petrol to diesel is rarely cost effective.
 
Hi to all,
I have located a pair of Mercruiser of 270hp 7.3 Diesels that are within budget. Would these give acceptable performance as a replacement of the 7.4 Bravo's?
 
I have read several threads on re-powering various boats, sometimes for more power, and more often petrol to diesel. The themes are always the same though......can I keep the same outdrive ? Will it give sufficient or improved performance ? Does it make economic sense ?

Re the same outdrive - my understanding is that the additional torque of a diesel vs a petrol motor makes hp a useless metric. Hence the talk of ratios on here already. If you have to re design your existing drive to suit, then you won’t be far off the cost of replacing with a re-con unit anyway.

As to improved performance. More hp and less weight will make your boat go faster. But more hp also means improving your drives or at least adjusting them to suit, and possibly changing your props (more cost) etc etc. In the case of the 270hp diesels, you are adding weight and reducing power........so performance is going to be noticeably less. Plus you will still likely have to at best adjust your outdrive gear ratios.....

Cost is very relevant. A diesel boat will have a higher resale value but you will have spent some serious £ to get there. Weigh up the amount of petrol you can buy with the money you’re going to spend, and also weigh up the fact that the boats value will at best go up by about half of whatever you spend. It’s a difficult decision to repower and you need to be sure you’re doing it for the right reasons.

You’re obviously a more than competent mechanic as you are planning on doing the work yourself but the outdrive theme on here suggests you need to be really certain what it is you’re expecting from your existing drives and whether they can deliver that.

Good luck !
 
Thanks for the feedback. Weight doesn't seem to be an issue in this case as both petrol and diesel set ups have comparable weights. I am concerned though about the reliability of the 7.3 diesels and a possibly significant drop in performance. While accepting that in this instance it cannot be avoided I wouldn't want to limit the boat's use in terms of carrying capacity.
 
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