Retrofitting VW automotive diesel

[hellosailor]

There are some air cooled VW diesels, used for things like pumping fuel from tanker trucks. I've heard of those being used on boats. But putting in a wet radiator system and enough airflow to keep that cool, and worrying whether you had materials that would stand up to the salt air...Dunno if I'd want to put that much time and effort into the kludge. Certainly not without seeing specifics from someone who had done it ten years ago and still wasn't having regrets.

[Scubaseas]

Some things you may want to consider.


You have a 5 ton boat with a 23.75 LWL. No matter how much HP you throw at it, it's not going to go faster than about 6.2 kts. If you put a 75 to 90HP engine in all you will do is push the stern/water line down. The boat won't go any faster than hull speed. It's a displacement hull.


If you keep your existing reverse gear it won't last long with 3X to 5X the HP it was designed for running through it.



Most guestimates I've ever seen call for engines of 2 to 4HP per ton for displacement hulls. So 10HP to 20HP is all you need.



The Volvo reverse gear you have now will have a hard time matching up to a VW. And a lot of other engines. You quite probably also will have to replace the prop and the gearing. Possibly the shaft too. By the time you get done with it, you might be able to rebuild yours for less than replacing to whatever.



There's nothing mystical about marine engines. If you're a diesel mechanic it should not make any difference if it's a Volvo a Yanmar or a Cummings or DD. Motors are motors. Nickel content is a lot higher in a lot of marine blocks/heads but the way they work is the same as land based motors.



Do you plan on keeping the boat forever? What happens to the resale value after you create a unique engine install?



Do you need to keep insurance on the boat? Will you be able to get insurance with non marine, self designed engine install? I have no idea.



Can you marinize and engine? Sure. Hard part is linking up the gearbox to the engine. Then gearing and propping it correctly.



Not saying it's a bad idea. Just not easy to find a donor engine in the 20 HP range and working it to fit.

[NorthCoastJoe]

I used to rebuild vw diesels the lowest HP was 48 they have gone up since those days. If you over heat it once the head gasket blows and you need to surface the head to make it right, not gonna do that yourself. I would not waste my time trying to convert one. Get a used marine diesel.

[Antares Sky]

Originally Posted by nhschneider

We had a Pathfinder engine (a marinized VW Rabbit engine) and it was reliable and had a very low weight-to-horsepower ratio. There was a guy in Canada who did an excellent job of providing support for the engine - I don't know if he's still around.



I would encourage you to install a properly engineered marine engine.


Fair winds and calm seas.

My Bruce Roberts 345 has a1998 Pathfinder in it with just 316 hours on it. Really like the engine and how it is set up. Not a fan of the Hurth V gearbox thou!
You can still contact the owner via Email, but he does not have a website.
Been two years since I last talked with him.

[Thumbs Up]

Automotive engine power ratings usually state maximum horsepower and marine engines state continuous horsepower. So don't take to much stock in the automotive power ratings. But do take a look at replacing the cam with one that will give better torque at lower rpms

[reed1v]

Technically any diesel can be converted to ship use. Need an appropriate cooling system, exhaust system, noise dampening system, and ventilation system. By the time you retrofit a diesel; you would have been better off buying a marine diesel to begin with.

[chrismct]

So to catch everyone up on my shakedown cruise bringing my boat from Washington NC to Cherry Point NC about 75 nm. First issue was there was about 3 mph wind when there was any so we averaged about 7 knots with the motor running and sails up. When we turned to go through Goose Creek and the ICW we sailed directly into the wind with no real room to tack due to the channel width. Once we approached the exit of the ICW into Bay River we got a strong southwesterly wind. The gods decided they would not let us pass and lost all forward propulsion before I could even get the sail up.
The wind and current pushed us out of the channel, keel was hitting the bottom between wave sets. I played with the transmission, put her at max rpm and was able to get into the channel, dropped anchor and the motor gave out. I would have put up a sail and tried to get some forward speed but that would have pushed us back into the shallows. Needless to say, the Volvo MD6B is way underpowered when there are multiple parameters beating you up.

I played it safe and radioed the coast guard which was only about 3 nm from us, they towed us to a shrimpery called R.E. Mayo in Hobucken NC and stayed the night at their dock. The motor still runs fine but the transmission is done for, I can hear metal and just banging around when in gear. I purchased the Boat US platinum before this little trip and was towed the rest of way for free. Talk about an adventure.

I will be repowering with a larger diesel, probably Yanmar. I talked with the Coast Guard while they were doing my inspection and federal law prohibits the use of radiator cooled engines on pleasure craft due to the chance of possible coolant leaks into waterways. Keel coolers are an option but have to have no trace of coolant if tested. Used engines will almost always have some kind of contamination. Crate engines are a possibility but cost as much as a marinized diesel.

[hellosailor]

"and federal law prohibits the use of radiator cooled engines on pleasure craft due to"
I confess, I'm just too shiftless and lazy to memorize the entire CFR.
But REALLY? Can anyone find exactly what this supposed regulation says? Because there's an awful lot of boats with closed water cooling systems ("fresh" versus "raw" water) and in every one of those systems there is a heat exchanger, which is just a radiator that is immersed in the exterior raw water, and guaranteed to put coolant outside the boat if there's a pinhole leak in the heat exchanger tubes.
Radiator = heat exchanger = perfectly legal and commonplace, except for the secondary cooling medium. A radiator could leak into my bilge--but so could the engine oil pump and the fuel tank, and federal law simply prohibits the discharge of all that stuff, so a little (much less toxic) coolant should be nothing the CFR is concerned with.
Especially on recreational pleasure craft!

Now, who's got that code citation memorized?

[kmacdonald]

I have marinized a new Kubota D1105. I used a Bowman heat exchanger, jabsco water pump">raw water pump, and wet exhaust. The hardest part is the correct bell housing, adapter plate for gear, and damper plate for flywheel and gear. All parts are available if you know what you are doing. PRM gear. Complete gauge package. Less than $6500 and a day to put it all together. If you don't know anything about bell housings, engine back plates, damper plates, gear splines, etc you might as well buy a Beta for $12k. If you do know you can save quite a bit. As for an air cooled VW diesel, forget it.

[Warren149]

The simplest solution to the cooling and avoiding the radiator , and fan would be a keel type cooler . You would use the same engine driven pump and no salt water issues.
You can then mount the engine in the usual place .All the other problems are up to you.
Cheers warren
Keel cooler on Louisiana shrimp boat

[kmacdonald]

Raw water cooling is a great option for engines that are run a lot.

[chrismct]

all of these are great point. hellosailor also has a good point about the federal law and radiator question. Airboats have radiators and run coolant/antifreeze.

[MarkSF]

Just fix what you have. Get a rebuilt transmission.

[Stu Jackson]

Originally Posted by chrismct

I have read several forums and articles regarding retrofitting an automotive diesel as an inboard so here is my take on this and correct me if I am wrong.

>>>>>>>>>>>>>>>>>>>>>>>
with an oversized radiator mounted on the transom with an electric high output fan(s)>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Where does the heat go?

The boat sails upwind.

The boat sails downwind.


You're in the cockpit.


Think about it.

[MarkSF]

Originally Posted by kmacdonald

I have marinized a new Kubota D1105. I used a Bowman heat exchanger, jabsco raw water pump, and wet exhaust. The hardest part is the correct bell housing, adapter plate for gear, and damper plate for flywheel and gear. All parts are available if you know what you are doing. PRM gear. Complete gauge package. Less than $6500 and a day to put it all together. If you don't know anything about bell housings, engine back plates, damper plates, gear splines, etc you might as well buy a Beta for $12k. If you do know you can save quite a bit. As for an air cooled VW diesel, forget it.

What parts did you use for the water jacketed exhaust manifold? Could you get off the shelf marinised parts to fit, or did you have to fabricate them?