MARINE conversion?
 

to all,

has anyone here done a diesel conversion for a large boat using an Ford/IH IDI 6.9 or 7.3 NON-turbo engine?

fyi, i've been (for the last 2-3 years) designing a 3 stateroom/2 head 28' x 72' HOUSE-boat to retire to as my principal residence. fyi, the MV DUTCHESS SANALYNN wouldn't "plane" with a GE J-79 jet engine, so all i need is enough power to "displace the water" & get her up to hull speed. = i need at least 108 HP at the marine transmission, according to my calculations.
(fwiw, i don't think that any person could live long enough to explore/fish all the bays, rivers, flats & rivers in south TX & LA, at a speed of about 10 knots or less.)

i would like the houseboat to be diesel-powered, as i'm afraid of gas engines "out on the salt", due to fire hazards.

further, i've found a complete but totaled 1986 Ford F-250 IDI 6.9 (with less than 100K miles) PU near me, for 500.oo. - the engine starts up & sounds FINE!

IF you have actual experience in such a marine conversion & are willing to share your experience, please advise.

THANKS for reading this!

yours, tn46

I don't know for 100% certainty, but I don't believe there are any marine manifolds for those engines, among other parts that would be required for a correct conversion.

Depending on your fabrication abilities and budget, I guess anything could be put anywhere but in my experience you're better off sticking to engines proven in the maritime industry.

Perkins and Yanmar are two brands that are backwards compatible with just about every marine final drive on the market, have parts networks all over the U.S. and world, and will fit into the requirements you have set forth for not a whole lot of money if shopped for keenly.

Mr. Miyagi,

first, THANKS for your reply.

i'm planning to use DRY STACKS with conventional "auto type" mufflers, rather than water-cooled manifolds, as is common with shrimpboats & other "commercial" watercraft on the TX/LA Gulf Coast & a "keel-cooler" & a "homebrew" salt-to-freshwater heat exchanger (made of copper pipe) to cool the water for the engine.

as for your suggestions of a Yanmar or Perkins, neither fit my budget as:
1. those & similar used engines around here seem to be in the 3-5 thousand dollar range
&
2. many of those used diesels, which are within my budget, have significant internal saltwater corrosion.
(until fairly recently, marine diesel engines, around here, ran "raw water" for cooling. - in the last decade "keel coolers" have become common but there are still a LOT of "raw water cooled" engines out there for sale.)

yours, tn46

CUMMINS MARINE > anything else !!!

Okay, understood...up here in the NW boat engines and parts are all over the place....the colder water helps keep major internal corrosion at bay--seems like stuff lasts longer up here in the water than it does in the 'Gulf.

if you plan on dry exhaust and the homebrew keel cooling, it would probably work, depending on the final drive setup you plan on using.

Biggest thing is, as you are well aware, a boat engine is running at 100% load most of the time, so having robust longevity is important, unless you don't mind frequent engine-out services.

The old school NA IDI Navistars had head gasket issues when pushed hard...mostly stretched head bolts, but at any rate a high quality replacement gasket with new bolts torqued under the new Navistar/FoMoCo procedures would be recommended.

If you shop around, a used-but-not-abused Cummins 6BT or BTA from a 1st or 2nd gen Dodge truck, or other applications, can be had for $1,500, or even much less....I think that would be a better place to start. They convert easily into the marine package, whereas the one-off Navistar might prove to be a headache, unless you're planning on like a C6 transmission to 20 degree straight shaft final like some drag boats used to do--with a Powerglide, but same principles.

The Navistar/Ford idea is unique though, and I like unique. :c:

Mr Miyagi et. al.,

the MAIN reasons for my interest in converting the Ford IDI are:
1. my experience with the 7.3L IDI in my truck & the FACT that i've never had a minute of trouble out of it NOR have any of my friends who drive the early IDI engines had any "exotic problems" with theirs,
2. i'm SHORT of $$$$$$, being retired on a small pension,
3. i know how to work on the "old school cornbinders",
4. i know ZILCH about working with/on Cummins engines
and
5. the 82,ooo mile wrecked Ford PU is NEARBY & (now!) just 400.oo!

to ALL: has ANYONE actually tackled such a IDI project?

i'd sooner NOT be a "pioneer", as the bones of "pioneers" litter the desert. (CHUCKLE!)

yours, tn46

You won't be a pioneer in the sense, but you will be going down a road that has been tried before and didn't work out.

Mercruiser offered the 7.3 diesel in one of their option packages years ago, as did a company called Starpower Diesel.

There may have been a Yanmar badged 7.3 as well but my memory is fuzzy on it.

They didn't sell well, and didn't work out well, although I don't recall the grisly details on the whole affair.


The general opinions from those in the industry will be to stay away from the 7.3 in a boat, for a wide variety of reasons. Your mileage may vary, but it is what it is.

I did a Yanmar refit a couple years ago to a boat originally equipped with a gas engine. The majority of the cost was not the engine, but all the peripherals....granted my application of use is not the same as yours will be.


You can search at boatdiesel.com or thehulltruth.com to see if someone has done this before....I love the 7.3s in my Fords but don't think I'd like them in a boat. YMMV.

Mr Miyagi,

once more, THANKS for your response. - i'll check out those sites, too.

yours, tn46

I've thought about diesel boats too mostly in speed boats and fuckaround boats(Those speedboat cruiser things with the galley, bathroom and small hull sleeping area). I stile think a multi speed transmission could benefit a boat especially a transmission with mostly gear induction.

You're welcome, TN46...best of luck, it sounds like you've got a pretty cool project regardless!
:c: