1993 7.3 IDIT - Delete the turbo, replace injectors and use a fuel pump calibrated for 174HP?

[Rocknit4x4]

This subject was interesting to me yesterday so I googled a 7.3 idi marine engine and ended up on a boat forum where they were talking about this subject and boat speed - sounded like the best option was to use a prop drive / gearbox that would change the output rpm to the prop as changing prop geometry would make it perform less desirable at various speeds - they equated it to turbo lag. What I understood was that changing it to perform well at 2000 rpm as opposed to 3000 rpm would make the prop perform worse somehow at lower rpm’s. I read into the conversation that diesel engines in boats are better for slower boats and gas engines tend to work better for faster boats. Having said that I have zero knowledge in boats - but there were quite a few hits on the subject on google.

 

[KansasIDI]

@1991f2504x4 there is something called a Typ4 cam, aka loggers or torque cam, that would help.

 

[rreegg]

diesel engines in boats are better for slower boats and gas engines tend to work better for faster boats.

a lot of it is hull shape - a displacement hull like a sailboat has a max speed (like 6-8 kts) governed by the hull shape. A planing hull like a power boat does not have the same constraints. And who doesn’t like torque?!
Foiling hulls are beyond my comprehension.
I’m sure this is preaching to the choir for OP though.

Super cool project and NA makes sense here given ease of access (turbo idi vans are notoriously difficult?).

From my limited experience with marine diesels don’t skimp on exhaust and prop details but I cannot provide specific input

 

[quickster]

To the OP, if you choose to drop the turbo, pump, and injectors let me know. I turbo'd my '91 a few years back and need cores for the pump and injectors. I seem to have hit the wall when it comes to fuelling.

 

[1991f2504x4]

are we forgetting the idi was actually designed to run against the governer? yes the motor makes the most torque under 2000, sometimes it needs to be wound out like a detroit. lol these motors were in school busses that maxed 55 mph against the governer at 33-3400 rpm. in a marine application where unlimited cooling capacity is available, an NA engine or especially an NA'd turbo block will run full bore for a lot of hours. lack of oil or overheating will be the only things to kill it

Thanks for confirming my understanding the engine was engineered run @ rated HP and RPM for industrial / commercial service.

A marine closed cooling seawater / freshwater system is included in the kit. Seawater is pumped through a large heat exchanger to remove heat from the cooling circuit and dumped out in the exhaust. The oil cooler uses the engine coolant circuit as does the water cooled exhaust manifolds. I can tweak sea water pump volume and heat exchanger capacity but not expecting to need to do this as the heat exchanger is pretty large.

Keeping the heat out of the engine compartment is also a priority. I'll use 2 bilge blowers to pull the hot air out.

I will need to fabricate a different oil pan with 12+ quart oil capacity.

With the engine designed and equipped to manage the higher heat of turbocharged operation, I'm thinking I can safely use the 1992.5 NA pump calibrated for 185 HP. I'll put an exhaust gas temperature sensor in the exhaust to keep an eye on that

Still thinking that 2700 RPM is a good choice for continuous cruising.

 

[1991f2504x4]

@1991f2504x4 there is something called a Typ4 cam, aka loggers or torque cam, that would help.

Is the Type4 cam profile and timing published? What changes when this is installed?

Is there someone that offers this for sale or does it have to be custom ordered?

 

[IDIBRONCO]

I will need to fabricate a different oil pan with 12+ quart oil capacity.

International applications used two different types of oil pans. I believe that one is a 14 Qt. pan? Both styles are a front sump design though.
This is a picture of what I believe to be the smaller capacity International oil pan just for reference.

 

[1991f2504x4]

International applications used two different types of oil pans. I believe that one is a 14 Qt. pan? Both styles are a front sump design though.
This is a picture of what I believe to be the smaller capacity International oil pan just for reference.

Front sump is OK as the engine will be installed with the flywheel facing forward.

A cardan shaft will then connect from the flywheel to the inboard v-drive transmission that will drive a conventional shaft / propeller.

I may still chose to fabricate a pan from aluminum to better withstand the effects of salt water corrosion.

 

[chickenpot]

Thanks for confirming my understanding the engine was engineered run @ rated HP and RPM for industrial / commercial service.

A marine closed cooling seawater / freshwater system is included in the kit. Seawater is pumped through a large heat exchanger to remove heat from the cooling circuit and dumped out in the exhaust. The oil cooler uses the engine coolant circuit as does the water cooled exhaust manifolds. I can tweak sea water pump volume and heat exchanger capacity but not expecting to need to do this as the heat exchanger is pretty large.

Keeping the heat out of the engine compartment is also a priority. I'll use 2 bilge blowers to pull the hot air out.

I will need to fabricate a different oil pan with 12+ quart oil capacity.

With the engine designed and equipped to manage the higher heat of turbocharged operation, I'm thinking I can safely use the 1992.5 NA pump calibrated for 185 HP. I'll put an exhaust gas temperature sensor in the exhaust to keep an eye on that

Still thinking that 2700 RPM is a good choice for continuous cruising.

The pumps are all the same, the difference in HP is the WOT fuel delivery by the pump plungers. The measurement of the fully extended pumping plungers when the pump was built is what makes them print the HP rating on the valve cover. When you turn up the "fuel screw" it compresses a leaf spring which is the limit stop for the pumping plungers, allowing them to travel further outward, and displace more fuel. so whatever pump you have, you can just turn up (or down) the fuel to your liking via said fuel screw. monitor exhaust gas temperatures if you start to turn it up

 

[chickenpot]

see the difference in HP and part number is just specifying that plunger measurement

 

[1991f2504x4]

see the difference in HP and part number is just specifying that plunger measurement

Very cool.

I know this lazy but what would the maximum recommended exhaust gas temperature (EGT) be for a normally aspirated diesel engine?

 

[Nero]

Same as any engine. Something below the point where aluminum gets squishy. 1100 is max I'll ever push, but that's me.

 

[KansasIDI]

Is the Type4 cam profile and timing published? What changes when this is installed?

Is there someone that offers this for sale or does it have to be custom ordered?

Well, I think some place called the Oregon Cam Grinding Co. makes it, to my knowledge these are the specs…

increase the intake lift to 261 lobe lift/392 valve
exhaust remains stock with 253 lobe 380 valve

I had to dig quite a bit, but that’s what Russ said at one point, 2010 or so. More often he said the specs were a secret, but this seems to be the exception.

One could call the company I mentioned, and ask them if they ground cams for Russ Mathis, and that since he is now gone, if they’d be willing to sell one direct.

 

[Nero]

I dont understand how it's such a secret, cant someone take a cam and duplicate it based off lift measurements?

 

[KansasIDI]

I dont understand how it's such a secret, cant someone take a cam and duplicate it based off lift measurements?

I don’t know why it was such a secret, but yes, it should be measurable.

But, he was secretive about it, for some reason.