Diesel catamaran
 

Inboard people, what is the smallest clearance in an engine bay you’d consider acceptable? I’m looking at putting a 26 or 29 inch across motor in a 34 inch wide space. Engines being considered are Nappi Z270 and Steyr in line 6 290. Initial calculations put the boat topping out at 50 knots. If I see 50mph I’ll be happy at a fuel burn of 28gph. Looking for a long range yet trailer able offshore fishing boat with above water exhaust.

Mastry engine center is pretty much the go to on diesel power, especially performance diesel power. They powered Donzi's back in the day, everything from classics to 38ZX's and they have done some other really interesting projects over the years like single diesel installations with 2 outdrives. They will try to sell you Yanmars probably but I'm betting you will learn more on one call with them than anyone else

Do you have a hull brand or design in mind ? I take it you’re looking at something like a HydroCat hull that is a non air packing planing hull .

I can’t see the advantage of diesels and drives over the efficiency and reliability of todays 4 stroke outboards.

As far as the side clearance issue with the motors from my own experience I’ve had is it is a major inconvenience when you need to work on the motors with something as simple as replacing the zincs in the heat exchangers .

My buddy has a 44 Lagoon power cat with 400 something Volvos in it that I changed the oil and flushed the coolant that was a nightmare to do anything on the sides of the motors.

I ran commercial parasail boats back in the day for 20 years and have ran gas outboards and inboards and inboard diesels.

You can’t beat todays outboards. I sold my dads 2002 fishing boat with 5000 hours on the Yamaha 225 with out a hiccup.

I’m wanting to do a Kevlacat 3000 hull. It’s a planing hull and the 270 horse diesels I’m looking at burn 14 gph vs 25 on outboard. The biggest difference to me though is not having an outboard in the way while in gaffing fish. It’s aggravating dealing with a pissed tuna inches from the wheels

What are you going to do for drives ? Were you located ? Your stuffing a whole lot of weight into that short of a hull , had Kevelcat built any inboard boats ?

I ran a single Yanmar 4liter in-line 6 cylinder 300 horse yanmar diesel inboard in my 31 foot parasail boat back in the day. At 3000 rpm I was only burning 7 gph but I was only doing 12 knots and just over the hump. At full throttle and 21 knots at 4000rpm I was burning 15 gph.

if you want to cruise 50 mph your going to have the throttle mashed and will be burning 30 gph.

A inboard is going to have considerably less efficiency and more drag than an outboard.

I was thinking bravo 1x or 2x diesel drives. They are rated for 370 diesel horses so 270 shouldn’t be bad. I also cruise, not offshore racing. Kevlacat put 170 diesels in their 7.2 meter hulls and got better than 3 mpg and greater than 40 mph top end speed. Those hulls also bow steered less with the motors shafted forward a bit.

I bought a pair of 370 Yanmars from Mastry to repower a CC fishing rig. They didn’t have any interest in doing the installs, but I knew that upfront. To me the diesels are more economical for long range trips.


https://cimg5.ibsrv.net/gimg/www.off...e2b6a35be.jpeg

Did you convert an outboard CC or were you upgrading an older inboard with a newer inboard?

I will tell you right now having outdrives on a boat you’re going to be logging a thousand hours a year on is a huge costly mistake in $s and time. Even if you are not leaving the boat in the water there is too many points of maintenance and failure on them.

Number one point of failure on a outdrive is the gimbal ring steering and tilt areas I used to put 2000 hours a year on my parasail boats and the gimbals would be so wore out after 6 months you had to pull the motor and install a new transom assembly.

Best thing I ever did was going to a direct drive inboard but I should have ditched the diesel and stuck with a time proven cheaply replaced Chevy 454.

I started with outboards but that was before 4 strokes and the 2 strokes wore out fast under the heavy loads of the drag of a parasail. Too much load if you lost a motor would scuff a piston if you needed power from it.

I’m designing for 300 hours per year. Might go up substantially when my dad retires but I doubt it. 4000 hours a year is impressive. I hope to get 250-300 a year annually.

Have you ridden in many low speed cat designs ? Almost all handle atrociously as far as I’m concerned.
I’ve spent years and thousands of miles in a 22 SeaCat and though you go where no other 22 footer would go as we did across the Gulf Stream regularly with 4 people and a half ton of supplies and dive gear you had to respect the handling. Big Following seas will find you floating upside down if you don’t dial things back.

The 29 Hydro cat I’ve spent some time on and is a 10 foot wide boat that handled the best of the cats I’ve been in.

My niece has a SeaHunter 41 cat and it handles like crap because it has asymmetrical planning hulls. Obviously they didn’t look back in history and ride on a Blue Thunder cat.

We did it the hard way lol. Gutted an older performance boat and rebuilt as a CC.
Where are looking to fish?

https://cimg5.ibsrv.net/gimg/www.off...6b7c4af7e.jpeg
https://cimg6.ibsrv.net/gimg/www.off...d6a2fa77d.jpeg
https://cimg7.ibsrv.net/gimg/www.off...ad78db69d.jpeg

To me the only benefit of diesel is when you can’t economically power a larger boat with gas. The value of diesel savings is hardly ever recovered by the original owner and can quickly become a liability once they need service or repair. Think Caterpillar or Volvo. .

I spent 20 thousand on parts the first 2 years with my Yanmar 300 back in 2000. I know it wasn’t a Yanmar design like the 370 but all those light weight motors are usually marinized land motors.

I’ve ridden in a twin vee 260, world cat 280, world cat 230ccx, and eastward 2400 seaward. The Seaward is a 3000 with 6 foot lopped off the stern. Twin Vee and world cat 230 require a bit more handling to stay upright. 280 and 2400 have significantly higher tunnels. I like how they ride but dealing with angry fish on the planer rod makes me jealous of my buddy’s 32 Albe.

What was that originally ? Beautiful job .

Oh I agree, if I do another one I’ll do trip 300’s and call it good. But this one’s staying diesel.

Awesome boat hoodoo. I’m a nc fisherman. My offshore runs are 50-75 miles. I have a friend that occasionally trailers to the middle grounds out of FL. I’d be tempted to do that one day.

Yea the one advantage of the cat is no rolling in a sea at idle. How far you going offshore and what waters . If your familiar with Albamare why not go with one of those ?

I was going to say Outerbanks being you brought up Albamare . I used to parasail Kitty Hawk running out of the Sport fish docks back in the day and Corolla also. I use to work building boats for Paul Mann during the winter.

The albemarle weighs 14000lb or more ready for battle. I would need a wet slip. They dont power it with diesel anymore for a new build. Most new 31s are twin or triple high hp outboards. They also don’t come in a center console configuration. The old 31 trolled like a champ though.

Spearfished middle grounds a few times. Looking forward to running my newly acquired rig to spend a week out there this Spring slaughtering fish.
https://cimg0.ibsrv.net/gimg/www.off...fe269e161.jpeg
https://cimg1.ibsrv.net/gimg/www.off...a8c21f226.jpeg

Gotta take the dog out BRB.

I’m not familiar with that cat. NC is super snotty water I thought. Wouldn’t you be better off with a 40+ old school V?

Let’s do a slow run out to Pulley Ridge deep dropping.

unlimited budget, yes. Problem with sport boats is all the systems that have to be maintained. Buying used, all that crap comes with the boat. CCs have way fewer things to break. Then a 40 foot old school cc would have to be new with a 400-700k price tag. Since I’m interested in new construction, size is definitely a consideration. I also have no desire to deal with a wet slip. That’s the biggest problem. Trailering a 40 would take a 3500 truck, a goose neck, multiple permits and guts I don’t have.

My dad used to own a 48 foot sailboat that we cruised all over the Great Lakes back in the 70s and he used to repeatedly tell me to never own a boat you need to depend on someone else for dockage and storage and repairs.

50 years later I bought this trawler and a 37 foot sailboat after hurricane Ian The dockage and yard problems are never ending.

I hear you on older boats. I looked at enough 15-20 + year old boats that if you gave me them and 30 thousand I wouldn’t take them.

I would have never have bought my trawler out of auction if my buddy hadn’t just got done replacing almost every system on the boat and still it’s always something.

A nice custom Carolina boat 30 feet long and 10 foot wide with a shallow 10 degree bottom with a lot of rocker to carry a deep sharp forefoot is the ticket. A nice flared bow would be a plus .

where in NC ? You running out of Oregon Inlet ?

You need a boat that can carry the bow like this for those waters off Hatteras.

https://cimg1.ibsrv.net/gimg/www.off...3d88a054b.jpeg

Ok I see the cat your talking about has really tall sponson's which do well up there. I was thinking more like Calcutta’s. Are they configured for inboard power?

I take it you live up by Tampa / St Pete area Hoo doo with Calcutta .

That’s what I was wondering. I have a 246 world cat on the lift at home and only keep it because I have crappy water at low tide and it runs shallow. But it sucks with a quartering following sea. Anything less than perfect trim and it hooks pretty hard. We use it to run around the bay and sandbar stuff but rarely go way offshore with it anymore. I’ve been on an older 33 WC that was awesome though.

[QUOTE=Hoodoo 2.0;4905508]That’s what I was wondering. I have a 246 world cat on the lift at home and only keep it because I have crappy water at low tide and it runs shallow. But it sucks with a quartering following sea. Anything less than perfect trim and it hooks pretty hard. We use it to run around the bay and sandbar stuff but rarely go way offshore with it anymore. I’ve been on an older 33 WC that was awesome though.[/

The 22 SeaCat I ran around in for years was a World Cat design originally. Great boat for the size but 32mph was top speed withv130s .
Running in following seas with those skinny cats will raise the hair on your neck , if they hook hard you’re phucked as you know.

I have been caught running across the Gulf Stream a couple times in that 22 and even though running slow we got surfing down steep waves and surfing and hooking . Scary Chit

I was just looking for the Benchmark 38 that I was on in Miami boat show in 95 but few were made and they went out of business.

My choice would be a custom Carolina boat around 35 and trailerable with outboards.

If a cat a Hydro cat 29 with outboards.

in the US, I doubt think it was ever attempted. In Australia, they did great. The problem with USA made kevlacats is 2 or 3 different people made them. Only one knew his stuff on how to make an excellent boat the others had QC problems. The motor they put in can be powered up to either 250 or 270 hp. If they can do it in a 24, it would surprise me if I can’t use the same blocks in a 30

I haven’t hit 10 post yet so I can’t post links. Look up diesel Kevlacat. First thing that shows up of google is a positive review

the nanni 270 is only 250lbs heavier than a Suzuki 300. Including out drive. I figured a lower COG would actually help sea keeping. I think a few the 20 degree inboard boat makers including Albemarle went up on deadrise when they went to outboards. I figured that was compensating to a different distribution of weight.

I shoehorned a Cummins 6BTA, velvet drive trans, and Konrad 520 into my 26 foot pilothouse, 23degree deadrise solid glass fishing and dive boat. Clearance is about 4 inches all around, with more at the back, but the entire upper half of the engine is exposed with the engine box off. In retrospect I should have gone 6 inch clearance or more, but that would have been a major rework and starts to cut into fishing deck space. Think about changing filters and how much room you need to swing a filter wrench and the diameter of the filter for removal before going too tight on side clearances. My boat was set up for diesel sterndrive when I bought it, and switching to outboards would have been a major PITA and likely not given me the performance I required without high fuel burn. Diesel is $2 a gallon cheaper here so it's a major saving, I can fish a 10 hour tournament for under $200 in fuel.

looking at the kevlacat that has the steyrs, the hull curves upwards a bit. I could set up a remote filter manifold. Or it might actually clear better than I thought. Anything on the sides will probably suck. How often does a ecm go out?

I think your idea of doing 50 knots in a 8 foot wide 24 foot tall sided cat is a little unrealistic as they don’t handle well at high speeds unless in calm conditions.

They are a 35 to 45 mph cat tops.

You stated that the Styer diesel was only 250 pounds more than a 300 horse outboard but most 24s have nothing larger than a 200 hp outboard and most have 150s as the additional horsepower and weight does not yield that much more in speed .

As far as towing I towed my last diesel parasail boat daily 10 miles round trip with a 1/2 ton Chevy conversion van.
It was 31 foot and 11 foot wide but 40 overall with my inflatable on the back deck. Weighed in at 12 thousand and drew 3 1/2 feet to float it off the trailer.

Big difference in 24 feet going to a 30 footer for sea keeping and ride. I would look for a used Hydro cat and hang some new outboards off it. With a 10 beam there is a lot of room between the motors to fish
https://cimg7.ibsrv.net/gimg/www.off...9fc0bf8ed.jpeg

https://cimg7.ibsrv.net/gimg/www.off...014bb83ff.jpeg

The 2400 eastward is the 9.25 foot 3000 with 6 foot lopped off the back. The 3000s with 300s top end is 52-54mph light. Top speed is a good way to compare performance between engine packages. I’ve had calm enough for 40 mph on the ocean twice in 3 years. Most of the time I’m doing 30-35mph until I bottom out the 280, then it goes to 20. Just bites the best fishing boats are becoming classic models I’ll have to buy used, then redo them.

You’re not going to hang twin 300s off the back of that 24 foot cat much less add an additional 500 pounds in diesels . These skinny hulled Cats have very little buoyancy aft compared to a monohull.

As good as the cats ride a 24 foot cat isn’t going to ride better than a 30 foot v bottom in anything over 3 foot . Cats do eat up the light chop but I’d take my old parasail boat against a lot of boats in a 3-5 slugging through them at 16-20 mph.

My boat was an Ocean Pro 31 but it was a copy of the old Rybo Runner with the step taken out of it . Find a Rybo Runner and put a big diesel in the back with a v-drive and a Arneson with a giant swim platform on the back of it to cover the drive if your sold on diesel.

check this out. https://www.yachtworld.com/yacht/1989-rybo-runner-center-console-8342831/


https://cimg1.ibsrv.net/gimg/www.off...1c5c8b696.jpeg
https://cimg2.ibsrv.net/gimg/www.off...9d67eaeb5.jpeg
https://cimg4.ibsrv.net/gimg/www.off...f7429cbce.jpeg
https://cimg5.ibsrv.net/gimg/www.off...0558d5870.jpeg
https://cimg6.ibsrv.net/gimg/www.off...c3f30aa82.jpeg

https://cimg1.ibsrv.net/gimg/www.off...35fb414ba.jpeg