Repowering my 1980 46C

[dirtyboat]

I run a fishing charter out of Islamorada and am now faced with the decision to either rebuild my 8v71 TI's (original motors) or re-power with something different. She's got Allison Twin Disc 2/1 transmissions in her now and lots and lots of hours.

Question I ask you guys is what would you do?

A) Rebuild the Detroits from top to bottom. Should cost me around $30k and a month of downtime.

B) Cummings 6TBA Rated 330HP with twin disc trans $19,500 for the pair with exchange of the D's

C) Cat 3208 rated 375HP with twin disc for the same price , $19,500 for the pair with exchange of the D's

D) MAN 730's w/5114 Twin Disc Trans for $50k, no exchange.

E) Cummings 6CTA factory rebuilt ($60k for the pair, no trans)


I'm currently running a 2" shaft with 25"x26" 4 nibral props

[dsharp]

How far do you have to run to fish? You’re going backwards with most of your engine choices. The 3208 cats aren’t going to last long in a 46 for Hat. You probably have Allison gears not Twin Discs. Don’t have any experience with Mans but a 514 gear seems to be overkill. The Cummins are marginal unless you’re close to the fish. The 2” shafts should be fine. Not sure how much clearance you have for larger wheels

[riverrandy]

I love the Cummins 6CTA's I installed in 2013, but my boat is smaller and much lighter. The inline 6's don't build much midrange torque until the turbo is spooling. You may want to keep 8 cylinders. And in my humble opinion 2 strokes make more power. I feel like 871's rebuilt might still be the best mix.

That being said, I believe someone on this board changed out his DD 871s with Cummins 6CTA's in a 53 MY and is quite pleased with the result. Again I love mine!

...and discussion...

[Boatsb]

6CT at 550 hp or above . Anything below that is a waste. The boat needs some power and the first 2 engines on your list would not do well.

I'm not sure of the MAN option but I know they are expensive to maintain.

I'd not look at the detroits as an option unless none of the others will work out.

I've put 6C 450's in a 42 hatt and it ran nice. The 46 would need some more power. I believe the 550 is also electronic and runs quieter and smoother.

[dirtyboat]

How far do you have to run to fish? You’re going backwards with most of your engine choices. The 3208 cats aren’t going to last long in a 46 for Hat. You probably have Allison gears not Twin Discs. Don’t have any experience with Mans but a 514 gear seems to be overkill. The Cummins are marginal unless you’re close to the fish. The 2” shafts should be fine. Not sure how much clearance you have for larger wheels

Yes Allison gears. during the summer I run about an average of 70miles round trip everyday for 90-100 days striaght with a couple of days off here and there.

[dirtyboat]

I love the Cummins 6CTA's I installed in 2013, but my boat is smaller and much lighter. The inline 6's don't build much midrange torque until the turbo is spooling. You may want to keep 8 cylinders. And in my humble opinion 2 strokes make more power. I feel like 871's rebuilt might still be the best mix.That being said, I believe someone on this board changed out his DD 871s with Cummins 6CTA's in a 53 MY and is quite pleased with the result. Again I love mine!...and discussion...

Thanks!

[dirtyboat]

6CT at 550 hp or above . Anything below that is a waste. The boat needs some power and the first 2 engines on your list would not do well.I'm not sure of the MAN option but I know they are expensive to maintain. I'd not look at the detroits as an option unless none of the others will work out.I've put 6C 450's in a 42 hatt and it ran nice. The 46 would need some more power. I believe the 550 is also electronic and runs quieter and smoother.

Yeah that's what I'm worried about. I have nightmares about underpowering. I'm on a tight budget.Thanks for the reply.

[Cricket]

Since it's going to cost pretty much the same no matter what engine you install I would definitely go with a straight 6, will totally open up the engine room. Since it's a charter boat would get the most horsepower you can afford and then run them slow so they last a long time. Wouldn't go with the 3208's or the MAN's. We've been running 800hp CAT 3406e's with 1.5 to 1 TD45114a's on 2" inch shafts for 16 years without issue.

[jim rosenthal]

I would say a pain of recon M11s, or 3406Es. I agree that inline sixes will open up the engine areas; they also run smoother than V8s do. Call T&S Marine engines in Crisfield, MD, and see what Timmy can do for you on a pair of 3406Es- they are real workhorses and would fit nicely in that hull.

And I would not go with MANs or MTUs, there is hardly a more expensive engine to maintain. Cats or Cummins are your best bet.

[Pascal]

If you re happy with the Detroits and The performance is fine for your needs then a rebuild is probably the best option. Forget the Bs and the smaller engines. Forget the MANa unless one of your relative is a Man mechanic.

The only option are the C series.