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Dave9111 · 07-12-2020, 14:09

Quote:

Originally Posted by Dockhead

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 . . .

Attachment 228224

Obviously you have never been a salesman! :-)

**Dockhead** · 07-12-2020, 23:43

Quote:

Originally Posted by Dave9111

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!

His calculations are right. The temperature rises and falls by how much? How much expansion and contraction moving what volume of air? Carrying how much water?

MaineSail has totally busted this myth; he backed up calculations with actual experiments. Change of temperature between night and day causes zero "breathing in" of moisture even when the tank is not buried in the temperature-constant bilge. This is proven. You can see all this on MaineSail's site, MarineHowto.

The only mechanism which might cause some breathing in of moisture is heating of the fuel when you motor. The amounts will be tiny (you can calculate it), and do you do this every day? If anyone gets even one drop of water per season this way, I would be surprised.

Water in sailboat fuel tanks does not come from breathing. It comes through leaky deck fill o-rings, or comes in with the fuel. With my previous boat, with fuel fill set into the deck, I had to take water out of the bottom of the tank every year. My father attributed this to "breathing" and insisted that we top the tank off full after every time we used the boat. Nevertheless, the water kept coming in.

This boat, which I've had now for 11 years, has fuel fill raised above deck level, in the coachroof. I top off the tank at most two or three times a year, and try to leave the tank near empty over the winter so less fuel is aging while I'm using the boat less. Never a drop of water in the tank, or in the filters. That's just one data point, but it supports the result of MaineSail's research.

rslifkin · 08-12-2020, 05:11

Condensation in fuel tanks can happen, but it's never going to put any significant amount of water into a tank. It doesn't happen every day, only when a large enough temperature swing happens. And even then, as others have mentioned, it's a tiny amount of water even at worst case.

I have much bigger tanks than most on here, and even then, the only time I've seen any hint of water in a filter was traced back to a slightly weak deck fill o-ring and a very heavy rain.

sailorboy1 · 08-12-2020, 05:30

In the end does it matter whether an engine from the the 70s/80s is gas or diesel? Isn't all that matters is the current condition of the engine and its fuel system?

LakeSuperior · 08-12-2020, 05:37

It only matters from the point of view of availability of spare parts. For example, imagine having a brand new A4 in perfect condition from 1964.

In the extreme, if there were zero spare parts available would you want to take it as your main source of power on a 5 year cruise?

sailorboy1 · 08-12-2020, 08:24

Yeah, but I bet a gas or diesel engine original to an 70s/80s boat probably has the same spare availability Of spares

Mickeyrouse · 09-12-2020, 06:29

I would point out to those who post in this thread ( aka The Topic That Never Dies) an article in Soundings Online, Oct. 6, 2020

https://www.soundingsonline.com/news...rk-harbor-fire

regarding an all-to-typical fire from a gas-powered boat spreading to the dock, burning up 4 other boats and the local tiki bar. If you want gasoline on your boat, keep it- far from me.

Dave9111 · 09-12-2020, 07:28

Quote:

Originally Posted by Dockhead

His calculations are right. The temperature rises and falls by how much? How much expansion and contraction moving what volume of air? Carrying how much water?

MaineSail has totally busted this myth; he backed up calculations with actual experiments. Change of temperature between night and day causes zero "breathing in" of moisture even when the tank is not buried in the temperature-constant bilge. This is proven. You can see all this on MaineSail's site, MarineHowto.

The only mechanism which might cause some breathing in of moisture is heating of the fuel when you motor. The amounts will be tiny (you can calculate it), and do you do this every day? If anyone gets even one drop of water per season this way, I would be surprised.

Water in sailboat fuel tanks does not come from breathing. It comes through leaky deck fill o-rings, or comes in with the fuel. With my previous boat, with fuel fill set into the deck, I had to take water out of the bottom of the tank every year. My father attributed this to "breathing" and insisted that we top the tank off full after every time we used the boat. Nevertheless, the water kept coming in.

This boat, which I've had now for 11 years, has fuel fill raised above deck level, in the coachroof. I top off the tank at most two or three times a year, and try to leave the tank near empty over the winter so less fuel is aging while I'm using the boat less. Never a drop of water in the tank, or in the filters. That's just one data point, but it supports the result of MaineSail's research.

Water accumulation in diesel fuel tanks is a REAL PROBLEM.

Plus, once it gets in there (and it will), bugs will grow!

Not so much in a gasoline fuel tank since gasoline has a vapor pressure which tends to keep moisture out of tanks IF you are using alcohol free gasoline. The Ethanol they add to Gasoline attracts moisture and causes all kinds of issues on vehicles (boats, tractors, old cars etc) that have vented tanks.

There are tons of links out there regarding moisture issues in diesel fuel tanks.

https://www.forconstructionpros.com/...voc-in-engines

https://www.tevisenergy.com/blog-com...s-and-engines/

Dealing with Condensation and Filtration Problems: A Guide for Diesel Boat Owners | Parker United Kingdom

I won't be surprised if gasoline powered auxiliary engines make a comeback.
New small diesels will need to be equipped with catalytic converters soon complete with DEF systems to clean out the converters. That makes a small diesel incredibly complex.

A small gas engine with direct fuel injection and a sealed fuel system (like modern cars) would eliminate a lot of issues. A catalytic converter would likely still be required but it would be a LOT simpler. There are some small gas engines being made now fuel injection on things like snowblowers, etc.

Amordobarco · 04-06-2021, 06:23

Have an Alberg 30 with the original atomic 4. 47 years old and still working great with no problem. In my opinion Diesels are expensive, and noisy. The problem with atomic 4 is usually lack of maintenance. There are many negative posts about the engine being an explosive hazard. Keep in mind most boats has gas engines . The explosion hazard is created by owners not maintaining or not knowing how to maintain a gas engine in a boat. As with most things that are hazardous.....people are the problem, not the equipment.

AndyEss · 04-06-2021, 12:29

Quote:

Originally Posted by Amordobarco

Have an Alberg 30 with the original atomic 4. 47 years old and still working great with no problem. In my opinion Diesels are expensive, and noisy. The problem with atomic 4 is usually lack of maintenance. There are many negative posts about the engine being an explosive hazard. Keep in mind most boats has gas engines . The explosion hazard is created by owners not maintaining or not knowing how to maintain a gas engine in a boat. As with most things that are hazardous.....people are the problem, not the equipment.

Most boats have gasoline engines? Other than our dinghy outboard motors, I don’t know of a single sail or power boat that has an inboard gasoline engine that I have met in many years.
And as for people being the problem, rather than equipment, you have a small point. However, equipment with fuel that is inherently dangerous, volatile and potentially explosive (with fumes similar to TNT in terms of explosive power) you are just asking for problems in having an inboard gasoline engine to power any decked boat.

Amordobarco · 04-06-2021, 12:44

Quote:

Originally Posted by AndyEss

Most boats have gasoline engines? Other than our dinghy outboard motors, I don’t know of a single sail or power boat that has an inboard gasoline engine that I have met in many years.
And as for people being the problem, rather than equipment, you have a small point. However, equipment with fuel that is inherently dangerous, volatile and potentially explosive (with fumes similar to TNT in terms of explosive power) you are just asking for problems in having an inboard gasoline engine to power any decked boat.

You are asking for problems if you fail to maintain a gas system in a boat.
It’s very simple

rslifkin · 04-06-2021, 12:54

Quote:

Originally Posted by AndyEss

Most boats have gasoline engines? Other than our dinghy outboard motors, I don’t know of a single sail or power boat that has an inboard gasoline engine that I have met in many years.
And as for people being the problem, rather than equipment, you have a small point. However, equipment with fuel that is inherently dangerous, volatile and potentially explosive (with fumes similar to TNT in terms of explosive power) you are just asking for problems in having an inboard gasoline engine to power any decked boat.

Just about every express cruiser you see under 35 - 40 feet has 1 or 2 gas inboards. I've got 2 gas inboards in my own boat as well. Looking around my marina, there are maybe a half-dozen powerboats with diesels, plus all of the diesel sailboats. Every other powerboat with an inboard or sterndrive is gas.

AndyEss · 04-06-2021, 13:53

Quote:

Originally Posted by rslifkin

Just about every express cruiser you see under 35 - 40 feet has 1 or 2 gas inboards. I've got 2 gas inboards in my own boat as well. Looking around my marina, there are maybe a half-dozen powerboats with diesels, plus all of the diesel sailboats. Every other powerboat with an inboard or sterndrive is gas.

https://www.boats.com/on-the-water/boat-engines-choosing-gas-or-diesel/
“ Regarding sailboats, I haven’t seen a gasoline-fueled sailboat with an inboard engine since the late 1970s, so sailors will really never have to ponder this.”
“ Smaller inboard or stern-drive powerboats up to about 30 to 35 feet in length will typically only offer gas engine power. But when you get into the bigger size ranges you'll often have choices. Beyond about 45 feet, you’ll really only have one choice, and that will be diesel.”

Atomic-4’s were last built in 1984. Graymarine last built a small boat sized gasoline marine engine in 1967.