Repower Opinions

[harnett]

Guys,
I am strongly considering a repower on my 53C. After getting quotes I've narrowed things down to Cummins Recon Engines and zf gears. Cats were over 30k more exspensive. Ok, that being said, here what I'd like input on. If I win the lotto this week I'll likely go with the 700 HP QSM. What I'm considering doing until then is the 500 or 600 hp QSC. A lot less money. This would give me the same HP as my 12v71 with about 10k lbs less weight. I normally run at displacement speed anyway but I want to be able to plane out occasionally if needed. I think with the same HP and less weight I should get at least as good performance as I have now. Might go to taller gear and 4 bladed props to help as well. Won't this work? Is this idea totally nuts!!

[cenger]

Curious why you want to reporter versus rebuild your 12v71’s. If you want more power you can get it from the Detroit’s. Hatteras did a Covington conversion on 1271’s that produced 845 hp.

[harnett]

I'm going to keep the boat a long time and the advantages of modern engines is just to great. Fuel economy, noise, cleanliness, space in the engine room, weight savings, etc. All in the cost difference isn't that great. To me the rebuild just doesn't make since.

[Boatsb]

First the QSC is 8.3 liter vs the QSM at 11.

If that's not nough of a reason your not looking at it right.

The qsm11 would be a great option and it does come in lower hp versions. The QSC would be too small in my experience and would not give you the performance a sportfish should have. Why repower if your not getting the benefits.

[harnett]

Are you saying that you don't believe a 600 HP QSC can give the same performance as a 500 12v71N even considering the 10k reduction in weight. Is there a technical reason you believe that? What performance a sportfisher should have is an opinion but if there is a technical reason equal or greater hp can't give the same performance with less weight I'd like to understand that better. Also I've been told that one piece shafts and four blade prop are going to gain a bit themselves. Again, I don't want to go faster, just equal to my current performance.

[Boatsb]

A 1271 is about 14 liters. The QSC is 8.3.

A 1271 was at a low power output for the machinery at 500 hp. An QSC 8 3 is at its top.

Will it work? yes. Will it work well? I dont believe so. You will get less than impressive performance with that combination.

Also consider the transmission ratio and shaft size before making a final decision.

I'd say you should consult a real expert (cummins factory or good repower specialist)

[harnett]

Thank you for the input. Yes I am working with a repower "expert". The local cummins dealer. He has done two Hatteras's boats this way. A 53 motoryacht and a 58. Equal hp/ smaller motors. The 53 performance was the same and the 58 actually ran 2 knots faster than factory power. I thought I would call Cummins engineering. At one time they had a 53c as a factory test boat. Thank you for your input. This is a big project that I will be living with a long time so I want to gather as much info as possible. Don't want to screw this up.

[Boatsb]

2 motor yachts are a poor comparison.

A company that repowers sportys would be a better measure. Most sporty owners dont repower a slow boat to stay a slow boat.

Im woking on a 42 Ocean repower for a customer and we have been discussing the new cruise speeds with different engine packages since day one. Not one discussion of similar performance.

A convertible is usually looking for another few kts cruise.

Theres a few members that repowered 53C boats with QSM11 engines who may chime in.

[Cricket]

There's other Hatteras convertible repower threads on here to review.
Since I'm one of the few that have been down this road my advice is to go big or it won't be worthit.There's alot of tricks to a repower so you want to hook up with an outfit or crew that does lots of them. Where are you located or where do you want to do the work? The in and out cost is pretty much the same no matter the size; and you're only going to want to cut the cockpit bulkhead once..
As I've posted before the QSM's are a good option; but I'm a CAT guy. Try looking for some rebuilt/reman 3406e/c15 @ 800hp/850hp or rebuilt/reman c18 @ 850hp/1000hp. Or possibly a new set of the the CAT 12.9 @ 850hp/1000hp. For me the key is to put in as much HP as you can afford and then take it easy on them and they will last forever.

[Boatsb]

Dont forget series 60 detroits. I believe 825 hp.

The ones I've been around run great.