Atomic 4 vs. diesel ?

[Island Time O25]

My own "anecdotal" experience.

My first boat 15 years ago was an early 80s 27 footer with Volvo MD5A. Being a newbie owner I did practically no maintainence on that little workhorse and 3 seasons later at Spring commissioning it became a runaway, I had to kill it through fuel shut off and upon inspection turned out the gaskets blew, the oil in the engine became the consistency of grey mud or worse. I did have a buddy who was a long time diesel mechanic and my first impluse was to hire him to do an engine overhaul. But quick research turned up that just the ovehaul kit was over $1,500, plus labor, plus loss of sailing season or most of it. Not worth it on a boat valued at a few thousands.

So we took the engine out (btw still have it at firend's backyard in NH so if anyone needs one for parts or scrap you're welcome to it ), put a bracket on the IOR sloping stern (had to improvise a wedge insert) and put a used 9.9HP Evinrude long shaft. The brackett was $50 used, the o/b $200 used. Install was done in a day by me and 2 marine pro buddies for the cost of a good lobster dinner with plenty of drinks.

After a 1.5 seasons I have figured the outboard is not to my taste. As I did not use the motor much the gas got stale fast. Also at any chop the cavitation was considerable, as the boat was now without the stabilizing weight of the inboard. We did calculate raised stern by about an inch due to engine removal but must have miscalculated a bit and this made the difference. Also the o/b itself was finicky and capricious although each time the issues were not fatal but still some sailing had to be curtailed while I tinkered with the motor.

A few years later, after I upgraded to a 36' with a Universal 5432 I was looking for a smallish boat in 25-30' range to take down ICW to Florida. In comes a very nice early 80s 28' from a charity for $1,500. But it was November, my diesel mechanic buddy already left for Southern climes for the winter and after the Universal 5411 didn't start or even turned, I figured we will bring it to life in the Spring. The boat was in very good shape for its age, sails very crisp, practically new and the price of the boat was less than the value of the newish sails.

Comes the Spring and me and my buddy go to the boat only to find out that the engine is seized (most likely this was the reason the boat was donated) and we start looking for the overhaul kit. After a few inquiries turned out this would be not only pricey but time consuming as the engine was almost 40 years out of production and the parts from its newish Universal replacement models were not 100% compatible. Or so they said, perhaps to push the sale of a new engine.

Out comes the old 5411, in comes also old Yanmar 2QM15. My buddy checked QM out while it was still on another boat in the same yard, pronounced it healthy and recommended it replace the 5411. The only significant issue were the engine mounts which had to be re-alligned. Which I accomplished on one hot early June weekend. Messy job but very informative and did much to improve my learning curve. My buddy said he was pleasantly surpised and did not expect me to do a decent enough job.

Not including my time and my already existing supplies of f/b cloth and epoxy from previous jobs, used Yanmar cost me $750 including the yard lift time, plust $600 to my buddy for 2 days of work and $150 for the correct used but like new prop. After a few coupling adjustments in the water the Yanmar worked as it should. Meaning yes shaky and noisy as any 2-banger but reliable.

Unfortunately after all this work and after a few seasons of still not taking the boat to Florida I realized moving the boat to FL was going to be a pipe dream I regretfully sold it as it was consuming too much for winter storage and summer mooring costs.

My 3rd anecdote is about A4. Another buddy got the late 70s Pearson 30 this May. He had narrowed his choices down to 2 P30s. One with a Yanmar for $8K and another with A4 for $3K. I was advising for the diesel one offering to help him haggle it down to $5-6K but he said being a motorcycle buff he felt confident tinkering with A4, if needed. This Summer the few times I went out with him for a day sail we had issues with A4 each time. Plus he tells me most of his outings with the family there were also some issues. Nothing major but enough to either postpone some weekend sails or curtail sailing travel plans. Sure, there is no guarantee that an old deisel would not have its own issues but what I've seen of his A4 further convinced me to continue vigorously advocating against it.

When buying a vintage 70-8os 30'sh boat the price difference between A4 and a diesel is not so great as to compensate for the A4 headaches. Not to mention the long run savings, reliability, etc. My 40 year old QM was infinitely more reliable then his 40 year old A4. And that alone should be reason enough IMO. Your mileage may vary.

[SalingSue]

How many people with a diesel have converted to a atomic 4??

How many with a atomic 4 have converted to diesel?

There ya go

[cal40john]

Originally Posted by Mickeyrouse

The 100’s of thousands of boats that today use gasoline are overwhelmingly outboards. Very few boats with inboard propulsion are launched new with gasoline engines. Other than conversions, I can’t think of any marine gasoline engines that are even available, though there are surely one or two, not counting stern drives. I too still use some gasoline- it’s for my dinghy, and that tank never gets off the stern above decks.

I’ve insured through BOATS/US since the mid-eighties. They used to send a newsletter periodically with safety tips and stories of dramatic losses. Seems like almost every issue had an item of some sailboat or power boat that burned in a dramatic way. Gasoline was often mentioned, though I doubt they ever identified the engines.

How many boats are sold in the under 35 foot range vs over 35?

https://www.boats.com/on-the-water/b...gas-or-diesel/

To begin, you’ll discover that powerboat builders will typically only offer choices of gas or diesel on boats in certain size ranges. Smaller inboard or stern-drive powerboats up to about 30 to 35 feet in length will typically only offer gas engine power.

[Dockhead]

Originally Posted by guyrj33

First the whole diesel vs. gas thing.
Imagine you own a boat yard and someone comes in with a gas engine sailboat with engine issues. Do you fix the gas engine for a couple of hundred bucks or do you spin a tale about how unsafe gas is and up sell a 10k diesel?

So you think the dangers of gasoline are invented by boat yards as a way to sell diesel engines? Seriously? I thought I'd heard everything . . .

Originally Posted by guyrj33

Diesels run excess fuel past the fuel injectors and return that extra fuel to the fuel tank effectively warming the diesel fuel tank. Why does this matter? Imagine you motor for the last 30 minutes of your day trip and then anchor or dock. It's the end of the day, the sun is setting and the air is cooling, so is your fuel tank and as it cools it pulls in the cool moist air outside of the boat. That moisture condenses inside your fuel tank, and it it's a diesel tank water encourages slime growth.

That's a well busted myth. Do the numbers on the amount of moisture which can be "pulled in" that way, and you will bust it for yourself too.

Originally Posted by guyrj33

. . . Should you buy a boat with a diesel?
Yes if stories about the danger of gasoline scare you, . . .

Ah, right. These are just STORIES, right, invented by boat yards to scare boaters into buying diesel engines? Right . . .

[LakeSuperior]

Originally Posted by Mickeyrouse

The 100’s of thousands of boats that today use gasoline are overwhelmingly outboards. Very few boats with inboard propulsion are launched new with gasoline engines. Other than conversions, I can’t think of any marine gasoline engines that are even available, though there are surely one or two, not counting stern drives. I too still use some gasoline- it’s for my dinghy, and that tank never gets off the stern above decks.

I’ve insured through BOATS/US since the mid-eighties. They used to send a newsletter periodically with safety tips and stories of dramatic losses. Seems like almost every issue had an item of some sailboat or power boat that burned in a dramatic way. Gasoline was often mentioned, though I doubt they ever identified the engines.

Thank you for nicely illustrating my perceived risk point in your last paragraph. In the 2019 Coast Guard accident report summary ignition of fuel and vapor was near last in terms of incidents. In 2019 there 4200 total boating incidents (613 deaths) of which 47 where attributed to ignition of fuel and vapors with no deaths.

There are roughly 11 million mechanically powered recreational boats in the US. Roughly 10 million are under 26 feet. So in round numbers 10 million are gasoline powered.

Clearly gasoline is more dangerous on a boat than diesel and the system must be properly maintained for continued safe operation. However, I think we are worrying about the 3rd decimal place when there are 1st decimal place issues.

[rslifkin]

Originally Posted by Mickeyrouse

Other than conversions, I can’t think of any marine gasoline engines that are even available, though there are surely one or two, not counting stern drives.

Mercruiser, Crusader, Indmar, Marine Power, and a few others still build gas inboards. A lot of them go into ski boats these days (as those are typically straight inboard, not stern drive). And some go in as repowers in existing gas powered boats. Tons of new gas stern drives out there in new boats as well.

[mvweebles]

Originally Posted by jt11791

And yet, something close to 95% of power boats use gasoline engines and I don't see them exploding all over the place.

A friend's boat from August 2019 on SF Bay. Their family owned the boat since new, probably 2005 model or so. He smelled something ahead of the fire. I forget exactly what went wrong - fuel pump malfunctioned or something.

The Moyer articles discuss how to minimize risk of gas aboard.

Boat was replaced with another gas boat.

Peter

[rslifkin]

Originally Posted by mvweebles

A friend's boat from August 2019 on SF Bay. Their family owned the boat since new, probably 2005 model or so. He smelled something ahead of the fire. I forget exactly what went wrong - fuel pump malfunctioned or something.

That kind of sudden failure underway is the one big thing that bothers me about fuel injected gas boats. Outside of a boat, I'll take EFI over a carb any day.

But something about the much higher fuel pressure makes me very nervous for how fast things would go wrong if a component fails while running. A carb (especially with a mech fuel pump that's designed not to leak externally if it fails) pushing 5 psi through a short metal line into the carb seems to have a much lower risk of a failure that would spew fuel into the engine room or against hot parts suddenly while running.

[Mickeyrouse]

Originally Posted by Dockhead

That's a well busted myth. Do the numbers on the amount of moisture which can be "pulled in" that way, and you will bust it for yourself too.Attachment 228224

Moisture will definitely form in a tank over night, enough to fill a fuel-water separator. It’s happened to me on several occasions. However, I don’t think it’s related to running the engine late in the evening or anything like that. Rather, I have noticed it happens on the sudden passage of a cool front, particularly if the fuel tank is less than full. Doesn’t seem to make any difference if the engine ran the day before or not. The water-saturated warm air in 24 gallons (or more) of space suddenly cooled really settles the water out. It will make no difference if the tank holds gasoline or diesel.
As far as excess fuel warming the diesel in the fuel tank....well, the return from the bleed-off is only insignificantly warmer than the raw fuel lifted from the tank. If you crack the banjo nuts on the injectors while running you can check this yourself. I suppose if you ran the engine a LONG time you could detect a slight warming of the reserve fuel, but not much.
Everyone should have a fuel-water separator, and they should be checked, especially after sudden drops in temperature.

[rslifkin]

Return fuel temperature varies a good bit depending on the engine, as does return flow. Some diesels warm the return fuel significantly, others only a little bit. And some engines only return a tiny bit of fuel to the tank, others return several times what they burn.

[LakeSuperior]

Originally Posted by Mickeyrouse

Moisture will definitely form in a tank over night, enough to fill a fuel-water separator. It’s happened to me on several occasions. However, I don’t think it’s related to running the engine late in the evening or anything like that. Rather, I have noticed it happens on the sudden passage of a cool front, particularly if the fuel tank is less than full. Doesn’t seem to make any difference if the engine ran the day before or not. The water-saturated warm air in 24 gallons (or more) of space suddenly cooled really settles the water out. It will make no difference if the tank holds gasoline or diesel...

Everyone should have a fuel-water separator, and they should be checked, especially after sudden drops in temperature.

You are making stuff up here. Any reasonable calculation show that what you are saying is not physically possible.

Start by estimating the amount of water at 100% relative humidity at say 80 deg F. in your 24 gallon empty tank. That is the total amount of water that could condense in your tank. Then estimate the amount of water in the air at 100% relative humidity at say 60 deg F. The difference between the two is the amount of water added to the fuel for a 20 deg temperature drop.

But since your tank and remaining fuel start at the 80 deg. They have to cool to condense moisture. If the tank is under the floor near the engines operating it probably takes a fair amount of time to cool.

Also consider the number of air changes per hour with air flowing into the tank from the vent. This is the replacement rate of humid air where some could condense if the tank remains colder than the air. I think you will find that nowhere near the amount of water you are estimated could be condensed into the tank.

[Mickeyrouse]

I suppose I am imagining that I have on numerous occasions experienced what I have described, first observed about 25 years ago, and as recently as two weeks ago, Particularly when checking the separator the day before. It doesn’t take but about 8 -10 ounces of water to fill the bowl in a Racor., and since the pick-up point is the lowest point of the tank, and since water is heavier than fuel, any water will be picked up first, to rest in the Racor. At that point the engine doesn’t run until the water is drained. I would point out a temperature drop not to 60 deg F. but 40 deg F., thus a 40 degree temperature drop. Have you ever seen the drip pan under an air conditioner or dehumidifier? Don’t forget that as the air cools it is contracting, bringing a new supply into the tank thru the vent to provide even more moisture. I am sorry to tell you I have seen this happen overnight on more than occasion. You may not accept it, but when you engine refuses to run after cranking, check your filter if you have one.

[LakeSuperior]

Originally Posted by Mickeyrouse

I suppose I am imagining that I have on numerous occasions experienced what I have described, first observed about 25 years ago, and as recently as two weeks ago, Particularly when checking the separator the day before. It doesn’t take but about 8 -10 ounces of water to fill the bowl in a Racor., and since the pick-up point is the lowest point of the tank, and since water is heavier than fuel, any water will be picked up first, to rest in the Racor. At that point the engine doesn’t run until the water is drained. I would point out a temperature drop not to 60 deg F. but 40 deg F., thus a 40 degree temperature drop. Have you ever seen the drip pan under an air conditioner or dehumidifier? Don’t forget that as the air cools it is contracting, bringing a new supply into the tank thru the vent to provide even more moisture. I am sorry to tell you I have seen this happen overnight on more than occasion. You may not accept it, but when you engine refuses to run after cranking, check your filter if you have one.

OK I did the calculation for you. In 25 gallon volume if the air at 100 relative humidity and 30 deg C (86 deg F) goes to 5 deg C (41 deg F), a 45 deg F drop in air temp and for now, ignoring the volume change, there is a maximum of 1/100 of a cup of waters worth of condensation.

That is there is 0.15 tablespoons of water or 0.08 oz of water. It would take about 100 times the volume of the fuel tank to make 8 oz of water.

This is by far worst case because it is unlikely that the tank will cool that far being inside the hull and surrounded by hull at near water temperature.

The reason why AC units drip so much water is they are cooling volumes that are 10,000's of times larger than your fuel tank at a constant input temperature for the air.

Disclaimer: I didn't go back and check the calculation but it roughly seems correct based on doing this 5 or 10 years ago.

[Dave9111]

Originally Posted by SalingSue

How many people with a diesel have converted to a atomic 4??

How many with a atomic 4 have converted to diesel?

There ya go

That's not the question. The question is; In an old sailboat, is an Atomic 4 preferable to an old diesel engine.



My answer is: It depends. Can you still get parts for the old diesel?

If not, you just bought an unrepairable engine.

[Dave9111]

Originally Posted by LakeSuperior

OK I did the calculation for you. In 25 gallon volume if the air at 100 relative humidity and 30 deg C (86 deg F) goes to 5 deg C (41 deg F), a 45 deg F drop in air temp and for now, ignoring the volume change, there is a maximum of 1/100 of a cup of waters worth of condensation.

That is there is 0.15 tablespoons of water or 0.08 oz of water. It would take about 100 times the volume of the fuel tank to make 8 oz of water.

This is by far worst case because it is unlikely that the tank will cool that far being inside the hull and surrounded by hull at near water temperature.

The reason why AC units drip so much water is they are cooling volumes that are 10,000's of times larger than your fuel tank at a constant input temperature for the air.

Disclaimer: I didn't go back and check the calculation but it roughly seems correct based on doing this 5 or 10 years ago.

You have erred in your calculations.
Sailboat and most powerboats have VENTED fuel tanks. As the temperature rises and falls the fuel expands and contracts in the tank. Also, the air density rises and falls (via barometric pressure). This causes the tank to breath in and out through the vent as the temperature varies. The air inside the tank is exchanged with air outside the tank. Then condensation occurs. The water is heavier than gas or diesel so the condensation falls to the bottom of the tank where it cannot evaporate. That's how water accumulates in fuel tanks. If this was not a problem, you wouldn't need a water separator!