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Surface drives on Diesels

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Old 03-31-2004, 02:30 AM
  #21
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Hard on, there was a Nortech 5000 with triple 440 Yanmars and #6s which was topping out at over 70 mph. Very nice boat it was, all white, cruises at over 60 all day with a range of 500+ miles. And you bet there are no problems at 250-300 hours! I have over 2200 hours on a quad set of 440 Yanmars. No problems at all and as far as maintenance is concerned, I change oil every 150 to 200 hours, change filters regularly, had to replace a few injectors and turbos. Apart from that, I really cannot complain. And the important part is the fact that those motors never let me down in use. Any intervention on them was purely voluntary as a precautionary measure...
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Old 03-31-2004, 07:49 AM
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Thanks Super T. A wealth of knowledge, I couldn't find that damn website.

The Q's I have are, if a 50 Nortech tops out at 70 with tripps, and a 43 runs 78 with the same power and #6's, with surface drives are they not more effecient on top end. What is the downside at the docks and getting on plane vs the #6.

Im more of twinn application guy, and wish there was a way that a reliable diesel would have more hp to get me closer to 80 vs 72 in a 4300. Im coming up with 580hp per side, is there a way to hop up the new 480hp diesel once warranty runs out, or are there mods like on our diesel trucks, that safely raise fuel pressure and play with timing. Thanks again Super T., Jeff
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Old 03-31-2004, 08:13 AM
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Jeff, check your e-mail. In terms of top end, surface drives will be more efficient. A 4300 with triple 440s and surface drives will run over 80, for sure. Probably somewhere around 83 mph. However, for reasons I stated in my e-mail to you, Trimax will accelerate better than outdrives or Arnesons. Around dock, it is true that surface drives will not be as effective as outdrives but you can't have everything. Is your boat intended for docking or for running fast offshore? Besides, it's a small price to pay because docking with surface drives is more a thing of habit than a real problem. Once you get used to it, you will not have problems. It may not be as good as outdrives, but it ain't really bad either. If you have triples, your outside shafts will be so far apart and that, with the immediate torque of diesels, means that you will be able to manoeuver your boat around the dock by using shifters alone.

As for twin vs. trip applications, apart from the cost, I don't see why people have a problem with triples. With big gas motors, there are plenty of issues such as excess heat etc. but with diesels, there are actually plenty of advantages. If you lose an engine, you are still likely to get on plane with only two motors running. With twins, if you lose one, you're stuck in trawling mode. I am used to quad applications and really see no problems. If you can afford triple 440 Yanmars, go for it. Naturally, there are always balance issues due to two props turning in one direction vs. only one prop turning the other way but this is not a major issue which would prevent me from going triple.

Yanmars can be bumped up to over 550hp and yes, it's the basic mods you would do to a diesel truck. It's not a tough job on Yanmars since they're all mechanical. I've done it and they last.

But if you want to use up your warranty before doing that, it's a long wait: 5 years.

Besides, if you have triples, enjoy 5 years at 80+ and just as it gets boring, tune them and go 90!
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Old 03-31-2004, 08:47 AM
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Super T, got your email, I will check out Trimax web as well. I appreiciate the time and knowledge, you have really helped me out as understanding about how Diesels work as well as surface drives. I will talk to Terry later on in the day. Thanks again, Jeff Jassby.
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Old 03-31-2004, 12:13 PM
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Not derail this thread, but wasn't Mercury (or someone) working to marinize the 7.3 Powerstroke at one time? I could swear I read about that somewhere...
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