Masterful

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.

VetteLT193

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

tommymonza

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.

Masterful

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

tommymonza

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.

Masterful

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.

Hoodoo 2.0

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.

Masterful

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

tommymonza

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.

Masterful

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.