IDI marine engine questions

I came across a 7.3 IDI boat engine locally for $250. The guy is selling it because the water-cooled exhaust manifold cracked and apparently they are impossible to find.

I’m interested in building an engine to drop in my truck, but I want to ask the group whether it would be a mistake to pick a marine engine as a starting point. Are the heads the same as the automotive engines? The cam?

When I did a search on this topic, the discussions seemed to center on the cooling system/accessories which of course are not compatible. If anyone has done this before or has definite knowledge on any important differences, let me know!

The block should be the same. The heads should probably be also. The water cooled manifolds should just be an all external bolt-on application. IP may have a different calibration, but again, that is bolt on. My guess is they used the standard IDI drillings and mounted their accessories on it. Worst case, you have more than $250 in usable parts, even if the whole engine is a dud.. Might be a van, or IH application oil cooler.. Depending on they year, you might even luck into it being a Factory IDI internals…

There was only a couple of companies that marine-ized the IDI, one of them was in Franklin Indiana, just south of Indy. In all the years I’ve been around IDI’s, I seen 1 brochure about them…..

Check the rotation. In twin engine marine applications, one engine is typically setup to spin counter clockwise. Not sure if any IDI's made it into twin engine boats, but many a Ford FE enthusiast has been disappointed to find out that the 427 side oiler he just found was the port engine in an old Chris-Craft and was setup counter-rotating.

snicklas said:

Worst case, you have more than $250 in usable parts, even if the whole engine is a dud..

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That’s what I’m thinking too.

FrozenMerc said:

Check the rotation. In twin engine marine applications, one engine is typically setup to spin counter clockwise. Not sure if any IDI's made it into twin engine boats, but many a Ford FE enthusiast has been disappointed to find out that the 427 side oiler he just found was the port engine in an old Chris-Craft and was setup counter-rotating.

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This is a really good point, I will try to find out.

Thanks for the good points guys, I’m leaning towards picking it up.

FrozenMerc said:

Check the rotation. In twin engine marine applications, one engine is typically setup to spin counter clockwise. Not sure if any IDI's made it into twin engine boats, but many a Ford FE enthusiast has been disappointed to find out that the 427 side oiler he just found was the port engine in an old Chris-Craft and was setup counter-rotating.

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They could just use it in a police car like the one at the end of the old movie "Moving Violations".

ROCK HARVEY said:

I’m leaning towards picking it up

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You should. I think I've seen someone say on here that those had more power than a regular, stock, ground based IDI.

I may be wrong but I think that if it is a reverse rotation, I would think a cam swap would be all that I required to switch it to standard rotation.

Worst case would be cam and injection pump.

Possibly just cam and injection lines, I'm not sure exactly what it would require. I am fairly certain that the block, rotating assembly, and heads are probably unchanged.

James

I reached out to the guy and if all goes well I’ll go pick it up this weekend. I’ll check any part number I find to see how they cross reference.

I went and picked it up today, and there’s good news and bad news.

The good:
- The guy had the heads gone through and resurfaced before he discovered the cracked and irreplaceable exhaust manifold, so I have a good set of heads!
- I got a parts manual for the marine IDI engines, so I can cross-reference anything and answer any questions anyone has
- I got a Navistar IDI shop manual, which I did not have a hard copy of before
- I can see crosshatching in the cylinders

The bad:
-I also see fresh scoring in the cylinders.
- The boat lived its life in Florida, and judging by the amount of rust in the heat exchanger I suspect it had water instead of coolant in the engine (no need for antifreeze in FL I guess). I will need to have the block checked for cavitation.
- the engine was disassembled and partially put back together, so I don’t trust that all the pistons, pushrods, bearing caps, etc. went back to the spots they were taken out of.

Honestly it was worth it just for a good set of heads. Any other usable parts are bonus. The shop manuals are extra bonus!

ROCK HARVEY said:

judging by the amount of rust in the heat exchanger I suspect it had water instead of coolant in the engine (no need for antifreeze in FL I guess).

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That's how they do marine engines. No antifreeze, just water. Fresh water always gets pumped through the engine from the outside. Some places in northern Florida, at least, do need antifreeze.

Antifreeze as the coolant would cut down the rust in the engine and any cavitation if the additives were used.
The heat exchanger works like the Oil Cooler in a way.

Any way, good score.

Goat

Rdnck84_03 said:

I may be wrong but I think that if it is a reverse rotation, I would think a cam swap would be all that I required to switch it to standard rotation.

Worst case would be cam and injection pump.

Possibly just cam and injection lines, I'm not sure exactly what it would require. I am fairly certain that the block, rotating assembly, and heads are probably unchanged.

James

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Piston Thrust. All the pistons will have to replaced (can't be spun 180 degs due to the Riccardo chamber) as well so the thrust side is correct for the rotation direction.

I haven’t dug into it yet since the initial inspection, but I’ll definitely check the piston part numbers to verify whether I can use them. I did see the boat and it was a single engine center console, hopefully that means the engine spins the right direction.