Gas to diesel conversion questions

[Krfoote]

I currently have a 25 ft offshore cabin with twin 165 HP mercruiser inline 6 engines, after sitting for several years before I purchased and parts were very corroded, I know I have to replace certain engine parts during the overhaul but I am considering pulling them and converting to diesel engines and some new outdrives.

The 165 is a great engine from what I am told but it's old and I am having a hard time finding replacement parts. So my questions are thus-

My boat is rated for 2x175 HP if I switch to diesel will I have to go to a lower HP because of the higher torque and performance, or will my rating change because of lighter engines?

And does anyone know where I can find replacement parts for an inline 6 that will ship overseas!

 

[jerryjerry05]

Re: Gas to diesel conversion questions

The diesels weight/power depends on what you decide you want.They make a lightweight 4 cyl that can put out 240hp.Yanmar I think.You'd probably need lower hp ratings.The cost is gonna be way expensive.Probably about 20-40k apiece.It would be cheaper to buy a diesel powered boat.
What parts do you need? There are some companies that will ship over seas.Where are you located(profile)?Cobe Marine in Pasadena,Md.They ship.Or should say they used to ship.Haven't dealt with them in a while.

 

[Krfoote]

Re: Gas to diesel conversion questions

I am in okinawa Japan, there are tons of engine and marine shops nearby but i dont speak japanese very well yet! i have already found several diesel engines for farly cheap but they were all to much HP to fit my boat. I dont necesarily WANT to switch i just want to get the best performance i can and am looking at all the options.

Right now the only Part that I KNOW i will need is a new fuel line, and at least 1 torque bolt on the header. Everything else so far is relatively good shape. but i havent gotten to deep into it yet and i am afraid it will only get worse.

 

[Don S]

Re: Gas to diesel conversion questions

Right now the only Part that I KNOW i will need is a new fuel line,...........
but i havent gotten to deep into it yet and i am afraid it will only get worse.

Just a few things to get you started.
You will need a flywheel cover with the Mercruiser engine mounts on it, this isn't an off the shelf part you can buy, it will have to be made to very tight tolerances for where the motor mounts are and the centerline of the crankshaft. Then you will have to modify an engine coupler to hook the engine to the drive.
Depending on the engine max speed of the diesel, you WILL have to change the gear ratio in the drive, and there isn't any gear available for diesel.
Then you have the exhaust system. Marine exhaust systems are water cooled and have water injected into the exhaust for cooling. How are you going to do that, again it would have to be special made, plus the exhaust tube on the transom shield will likely have to be redesigned for what ever engine you pick.

The is a lot more to it than just finding an engine.

 

[Krfoote]

Re: Gas to diesel conversion questions

Thanks For the Input, I am going to try to salvage the 165's and possibly upgrade the Outdrives, If i can find the parts i think that would be the easiest and cheapest. That Summit racing site seems to have an endless supply of everything so i have high hopes!

I like the idea of Diesel and redoing the whole setup but right now i jsut want a boat that i can get in the water with, Perhaps i can work on that kind of improvement in a year or 2.

 

[MCL]

Re: Gas to diesel conversion questions

I actually put a lot of thought to this.I currently have a 4.3 mercruiser with vortec heads with alpha drive,completely rebuilt and everything in shape.The reasoning for diesel are high gas prices and free veg oil.Mixing diesel with veg oil would cut my fuel costs to 1/5.

I thought about getting a mercedes om603 engine,its a 3.0 tdi 6-cyl mercedes engine used in the 90? with a mechanical injection pump.Dishes out 180hp stock and can easily be tweaked for more.The conversion would need a new custom made exhaust manifold and riser,larger turbo,Fresh water cooling and intercooler,fuel line and filter modifications,a adapter plate to fit the mercruiser flywheel cover to the block.Also a heavier flywheel with fittings for the coupler would be needed to spare the alpha drive from the diesels torgue and rough running.The engine idles at 850rpm and revs to 6000rpm so I dont see a problem with ratios,the idle could probably be dropped with the heavier flywheel.These conversions have been done a few over here,I dont have the time for it right now for it but would be a fun project in the future. I counted a rough estimate to roughly 5500e for a completely rebuilt engine+plus my own work,but everything is way expensive over here.

The only doubt I have is the diesel ripping the alpha drive apart.

 

[elkhunter338]

Re: Gas to diesel conversion questions

Are your 165's fresh water cooled? If not I would ? if the blocks are something that is rebuildable. If they are old and have been used in salt water I would guess the blocks might be something you do not want to stuff a bunch of money into.
Michiganmotorz will ship world wide, new in-line six for $3000 plus shipping.
I bet you can order manifolds and carbs and such on e-bay and other locations that will ship world wide.
You are going to have $1,000's of dollars to spend on old twin outdrives.