i have been thinking about putting a 7.3 or 6.9 idi diesel in a jetboat in front of a brekeley jetdrive...i would put powerstroke pistons in it to lower the compression ratio to 17.5-1 just like the powerstrokes, have a water-cooled intercooler with a holset hx45 or hx50--i think thats wut they are called-- with propane injection and shut the wastegate off so it will make like 50 lbs of boost. i think its in the "nobody says it can be done" category, but like my granny always told me, "anything can be done if you put your mind to it" i know it will have to have some kind of hellacious overdrive transmission, im thinking .50/1 will be good, but think about it, any underdrive tranny is an overdrive turned backwards hell, use a zf-5 speed and be jammin gears and blowin smoke on the water.... plus you can get farm diesel tax free, burn that red diesel up aint no black and whites on the water, cheap, it would stay together, look and sound cool and i think it could potentially haul ***** does anyone know for sure if a owerstroke piston would fit on a 7.3 idi??? do they make aftermarket pistons for this purose? do they make custom grind cams for these or can i have one custom ground?? i know the lift of the cam is a really pinche .25 or something and i couldnt even guess as to how low the duration is... idk ,maybe diesel cams are way different than gasolines, im not a cam guy anyways..oh, and does anyone know how to make a gallery, i wanna show ya'll my beat up 89'

 

Look for posts from "wellcraft" he has a 7.3 in his boat. Good luck and keep us posted and also keep the bank posted.

 

I would like to see it but are pistopns are flat tops and powerstrokes have a mix chamber I would say you could put some valve releifs in you pistons and drop them that way or get some from Mahle. get r done I want to see photos

 

nogo, could you tell me how to make a gallery or whatever, and are the powerstroke pistons dished, i know the idi pistons are flat as a panckake as well as the heads are flat, if i had dished pistons it would be better b/c the low compression can take more boost with less exh heat. if not could i install a milled 1/8 inch plate between the head and block with 2 sets of head gaskets, sounds kinda iff-y to me, what do you think

 

Now you're talking. Do you have a boat to do this to? I have a gas jet boat and thought it would be wild to build a diesel for one. It would have to be done for a conversation piece though, because you'll probably run out of money long before you ever get it over 35 mph.

I'm running an Olds right now with open headers at 4900 rpm just to get past 50. With a B impeller that works out to around 325 hp. You'd have to make a great deal more than that to power an overdrive box and a jet pump.

I'd still like to play with one someday though.

 

Malcolm, I have a friend floating around in the states somewhere who is crazy about building exotic machines. He used to run the salt flats and then twin turbo boats. Let me try to find him and he will have the answers for the power needed. Bill

 

I already have the answer, more than an IDI can produce. Heh-heh! Fast jet boats have close to, or over 1000 HP

 

im good at working on diesels, i understand them better than gasolines, i have been helping my grandpa and uncles work on them since i can remember and im still learning stuff about them every day, they are kinda "not so picky" like gasolines i guess, give it all the air and all the fuel you want too and as long as its timed right, it will go, oh i have been thinking about getting a fuel inj. pump off something like a 3208 or a 3408 cat v-8 it would look really kool on a jetboat and i think it would be better than the stock one anyways. i wish i could find a bosch pump, bosch pumps are the best you can get, does anyone know if bosch makes a v-8 pump? more fuel=more power as long as you can get enough air to it, maybe even nitrous or propane on top, i heard it is a real "diesel savior" cools down the exh. temp.

 

If I was going to overdrive straight through I would look at something like running a Suzuki Samuarai transfercase backward. You can get 4.80-1 gears for it, or run the factory 2.2-1 gears. It's lightweight and small so it wouldn't take the whole boat to fit it in. I would probably run a prop though, because they are much more efficient than a jet-drive. If you run the jet, you can change the impellers or have a custom one made. I think it would move out of the hole pretty fast, but it would probably run out of rpms and steam a little too fast. There are quite a few diesel powerboats that are running around. If I remember right they are running CAT diesels. The guy I saw claimed that he was getting the same speed as twin 502 chevy's with twice the hours between overhauls and 2-3x the fuel economy.

 

well i think that a .50 would be good, thats a 1:2 overdrive ratio, if i could get the motor runnin 4000, the prop wule be spinning at 8000and since nobody i know is running over 5500-6000 that are in the 70-80 mh range i can conclude that i would only have to get my diesel to run 3000-3500 that would put me at 6000-7000 range given the added weight of the diesel and t-case,...but it wouldn't be any different than hauling 2 extra people around, 2 full tanks of gasoline, and a set of tools which i won't need anywways, cuz its a diesel right? noone wants to ride in my clatterin'-*** jetboat

 

It sure would be nice to see the looks on peoples faces when an old IDI outruns a RAT.

I don't know about the piston issue, but I think you could probably figure out how thick the deck is on the heads and maybe mill a little dish in there to lower the compression a little if you had no other choice. Maybe if the tops of the pistons are thick enough you could mill a little off of them. The spacer idea is valid, but sealing it might be a little tough without fire rings ( copper o-rings or whatever it is that they are called nowadays)
For the cam, call crane or comp. They do custom regrinds on your old cam for a small fortune. If I recall correctly though, it's not very easy to cam a diesel. I might try some of the tractor pull sites or a call to Banks or something. Maybe if they don't have the answer for the cam, they might know somebody who does.
I also think that porting the heads and running a set of home-made headers into the turbo or twin turbo'ing it with a seat of headers would really wake that old motor up. That and a custom intake that would flow better than that joke of a casting that IH thought up. A custom intake might also allow you to put in some fuel injectors or nitrous type fuel/nitrous nozzles to help the fuel starvation under high HP.
As for the head gaskets. I think ARP makes a set of studs for this engine. Epoxying them into the block might make up for the small size, or drilling out the holes and finding 1/2" studs/bolts might help. Or it might hurt for all I know. Then you might find out that the bottom end would be the weak point, but it sure would be fun to find out.

Have I run my mouth enough yet?

I think it would be an awesome project. I myself thought of replacing the worn out volvo 4 cylinder in our boat with a Peugeot turbo 4. Same HP, much more TQ and better fuel economy for pulling a skier. No more worrying about fires and explosions from leaky 20 year old carbs and having points burn out half way across the lake.

Good luck.

 

I think you could make a 40 mph diesel jet pretty easy, but I wouldn't try for much more. If you look at an impeller chart, to turn a Berkeley B impeller 6000 rpm, you need around 600 hp. Then take into account the 50% overdrive, that sounds like at least another 300. I don't think there's anyway to get a 7.3 up there!

Still think black smoke rolling out of the headers would look cool though (unless you had to follow it up stream).

 

run your mouth all you want finlen, thats what this web site is for, now only if i had one of those talk and type thinga ma bobbers, that would make it a lot easier, my grandma would think im crazy talkin to the computer.. lol but put any ideas on here that you can think of, even if it sounds like a bad one, it could spark up a better one. does anyone know of a t-case that would alredy fit a zf 5-speed that you could put super overdrive ratio gears in it??? just another thought i had and lets see, wouldn't this diesel put out enough torque to turn an impellor 6000??? i know you would have to have a lot of power, but i thought it would be do-able, lets think about some real life numbers, say 600 ft lbs torque and 375 hp. 50% overdrive would increase hp by .50 and decrease torque by .50 i think im right on that so that would be 300 ft lbs and 750 hp. and how much loss would be through powertrain? 20 % would be 600 hp and 240 ft lbs at 6000 rpm, i think those numbers aren't too bad.... if someone thinks these numbers are garbage, they probably are.... i wasnt the honor student in math, but if they are then it sounds allright to me, since i think i can get a little more power out of that old diesel than that, maybe i need to be even higher than a .50, has anyone noticed these motors even in stock form pull better in o.d. than in direct or lower gear???? i have more torque at lower rpm, im gunna try it and see if it works, never know till you try, ill post pics if i ever get around to it and keep updated

 

Have you recently robbed any banks or is Bill Gates your dad? I'd love to fool around and build something like this, but I can't afford it. If I was doing something like this I'd want a whole junkyard at my disposal. The overdrive will steal hp and torque, I think you'd be better off getting it super balanced and building a lighter rotating assembly (somehow) then just turn it up to 4500. If you could get around 300 hp out of it at that speed and gear up to an A impeller, you might get somewhere around 50+.

I hate to be such a wet blanket about this, but I'm just trying to be realistic.

 

the cam in these diesels are not designed to run at 4500 rpm's, if you could make it run 4500 w/o blowing up, you wouldnt have a cam good enough for it, it would be like spending 5000$ on the bottom end of a chevy 454 that was good for 7500 rpm's and then putting a stock 210-218 cam shaft in it that is only good for 4000-4500 and trying to drag race with it, it would be pointless because the motor would not pull the hat off your head at 7500, you might get it to 7500 in first gear with 4.10 rear end, that sounds pretty realistic to me. i have some pretty good connections spectra. and i have thought of another idea too, hydraulic power, it would work really simple but there is nothing cool about it like jammin gears... but sounds like an efficient way to transfer power.... if i get a hydraulic pump and a hydraulic motor to fix to the input shaft on the jetdrive, it would save all the added weight of a transmission and overdrive gearbox, and at the same time save the valuable room needed to put this driveline. depending on size of pump and motor, it could be turned at any rpm you wish because hydraulic motors are simple enough and balanced enough to run 10 grand with no problem whatsoever, (im not saing im going to turn the prop 10 grand, im just giving an example). now, you would have to do a lot of figuring and trial-and-error to give it enough overdrive but not too much (just what the motor is cable of) and then get the right prop for it at the rpm you want it to run and viola that is all you are going to get out of it. not so little that the motor is wrapped out and has nothing to pull against, but not too much to where it will barely run, and i think i can get a little more power out of it than 300 hp... i said that in an earlier post, but i guess you overlooked that part. if all it will go is 50, well ill give it a really cool paintjob and cruize it around the lake. but i still want a diesel jetboat.