Dinghy Equipment?

[hawk232]

I can attest to a danforth "flying"!

A couple of years ago i was out scalloping in my flats boat when an afternoon thunderstorm carrying alot of wind blew in. I first tried to out run the storm but it caught me. Visibility dropped to a point where i did not feel safe to continue running along (and i was scared of other boats running towards me, that i wouldnt hear because of my own engine). DEPLOY THE ANCHOR!! wait, why is the boat still drifting so fast?? look out and see the anchor "skiing" downwind of the boat. tried muliple methods, including throwing the anchor as hard as i could downwind so that it would have time to sink before being yanked, all with no luck. This was in 7' of water... imagine in 20' how hard it would be to set!?!?

ended up motoring very slowly into the wind until the storm passed (in florida they blow out as fast as the blow in)

 

[jviss]

Try adding sea foam snake oil in every time adding gas and ethanol free gas mine been running great

There, fixed it for you!

 

[Kings Gambit]

The guys at the outboard repair shop in Costa Mesa, who have worked on my 5-hp Tohatsu 4-stroke a few times, have endorsed use of fuel stabilizers. But, the thing that matters most is to use fresh gasoline; not stuff left over from the last outing. And, to run dry the carburetor if the outboard will remain unused for longer than, say, a few days to a week. I pour the left over EtOH-gasoline (i.e., regular unleaded) into the car’s tank to get rid of it. Start with new gasoline each new trip. But in spite of that, I still have to have the carburetor serviced annually to bi-annually for best performance. Best performance is a good start after only two or three pulls max, and to idle w/o choking out, especially after throttling down to approach the anchored yacht.

Here’s that scenario again. You’re anchored in a remote place. It’s near dark or actually is dark; the wind is a steady 12 kt although dying. You and the Admiral are returning to your yacht after having dinner with your friends on their boat anchored 200 ft away. You’re over there b/c they did bring not their dink. You throttle down to approach and the outboard sputters out. Your momentum is checked almost immediately if approaching from downwind. Two pulls and engine doesn’t start. You apply some choke. Next thing, you smell gas b/c the thing is flooded. By this time you’re >100 ft downwind of where you are anchored, now in 40 ft, blowing to sea. Your pals are below; they never have the VHF on anyway when at anchor. You try shouting, but they are up-wind of you, etc. Remember, they have no dink to come fetch you anyway. Now what?? Start rowing. Good luck w/ that!! Maybe should add an air horn to my list in post #1.

 

[jviss]

I have switched to Cam-10 ethanol-free, 100 octane racing fuel, available at a pump near me; and also to Amsoil 100:1 2-stroke oil. We'll see. So far, so good.

 

[Kings Gambit]

I have switched to Cam-10 ethanol-free, 100 octane racing fuel, available at a pump near me; and also to Amsoil 100:1 2-stroke oil. We'll see. So far, so good.

The outboard guys and a couple of folks here have cautioned that burning high octane formula makes the engine run too hot. Might cause “catastrophic” failure w/o warning.

 

[Kings Gambit]

Here’s that scenario again. You’re anchored in a remote place. It’s near dark or actually is dark; the wind is a steady 12 kt although dying. You and the Admiral are returning to your yacht after having dinner with your friends on their boat anchored 200 ft away. You’re over there b/c they did bring not their dink. You throttle down to approach and the outboard sputters out. Your momentum is checked almost immediately if approaching from downwind. Two pulls and engine doesn’t start. You apply some choke. Next thing, you smell gas b/c the thing is flooded. By this time you’re >100 ft downwind of where you are anchored, now in 40 ft, blowing to sea. Your pals are below; they never have the VHF on anyway when at anchor. You try shouting, but they are up-wind of you, etc. Remember, they have no dink to come fetch you anyway. Now what?? Start rowing. Good luck w/ that!! Maybe I should add an air horn to my list in post #1.

Actually, in a case like that above, where friends/guests are leaving my boat after dark, especially in wind, I keep a Tac light (Bell & Howell Tac Light Pro) on them until they are safely aboard their boat.

 

[jviss]

The outboard guys and a couple of folks here have cautioned that burning high octane formula makes the engine run too hot. Might cause “catastrophic” failure w/o warning.

That is completely untrue, old wive's tale "bar talk."

Octane rating is a measure of a fuel's resistance to detonation. A higher octane rated fuel will not run hotter than a lower one. However, a particular engine may require a minimum octane rating to avoid premature wear and damage. Using a higher octane rating than required has no effect.

For example, this from Mercury's website:

IMPORTANT:

• Using fuel that is below the minimum recommended octane may reduce engine life
• Fuel recommendations are based on engines being set up and tuned to manufacturer's specifications. This includes using the correct propeller to allow engine to achieve recommended maximum RPM under typical load and conditions
• Leaded fuel is not recommended
• Fuel that exceeds 10% ethanol is not recommended

MERCURY & MARINER FUEL RECOMMENDATIONS

• Use a major brand of automotive unleaded petrol (ULP) with a minimum posted octane rating of 91
• These recommendations apply to Mercury and Mariner 2-Stroke, 4-Stroke, Verado and OptiMax models unless specified otherwise (ref to "Notes & Exceptions" following)

So, my 1986 and 2000 vintage 2-stroke 15HP Mercs require a minimum of 91 Octane. 100 will cause no harm.

 

[Kings Gambit]

That is completely untrue, old wive's tale "bar talk."

Octane rating is a measure of a fuel's resistance to detonation. A higher octane rated fuel will not run hotter than a lower one. However, a particular engine may require a minimum octane rating to avoid premature wear and damage. Using a higher octane rating than required has no effect.

For example, this from Mercury's website:

IMPORTANT:

• Using fuel that is below the minimum recommended octane may reduce engine life
• Fuel recommendations are based on engines being set up and tuned to manufacturer's specifications. This includes using the correct propeller to allow engine to achieve recommended maximum RPM under typical load and conditions
• Leaded fuel is not recommended
• Fuel that exceeds 10% ethanol is not recommended

MERCURY & MARINER FUEL RECOMMENDATIONS

• Use a major brand of automotive unleaded petrol (ULP) with a minimum posted octane rating of 91
• These recommendations apply to Mercury and Mariner 2-Stroke, 4-Stroke, Verado and OptiMax models unless specified otherwise (ref to "Notes & Exceptions" following)

So, my 1986 and 2000 vintage 2-stroke 15HP Mercs require a minimum of 91 Octane. 100 will cause no harm.

Just reading on this, higher octanes allow greater compression in the cylinder before combustion (detonation) than lower octanes. Higher compression should equate to higher heat content in the cylinder at the time of combustion, given that pressurization (compression) and heat production are directly correlated. More pressure, more heat produced. The other engine components such as pistons and valves will experience that excess heat. So, if not designed to run excessively at those heats—i.e., at high octanes—why not potential for catastrophic failure?

 

[jviss]

Just reading on this, higher octane allows greater compression in the cylinder before combustion (detonation) than lower octanes. Higher compression should equate to higher heat content in the cylinder at the time of combustion, given than pressurization (compression) and heat production are directly correlated. More pressure, more heat produced. The other engine components such as pistons and valves will experience that excess heat. So, if not designed to run excessively at those heats—i.e., at high octane—why not potential catastrophic failure?

Higher compression, correctly stated as compression ratio, is something designed in to the engine, i.e., a function of bore, stroke, and combustion chamber volume. Changing fuel can not change compression ratio.

A higher octane fuel is necessary for engines with high compression ratios to prevent detonation, i.e., knocking, which can damage the engine. As I said earlier, using a higher octane fuel than an engine requires has no ill effect, except to perhaps cost more and therefor waste money.

 

[Kings Gambit]

Higher compression, correctly stated as compression ratio, is something designed in to the engine, i.e., a function of bore, stroke, and combustion chamber volume. Changing fuel can not change compression ratio.

A higher octane fuel is necessary for engines with high compression ratios to prevent detonation, i.e., knocking, which can damage the engine. As I said earlier, using a higher octane fuel than an engine requires has no ill effect, except to perhaps cost more and therefor waste money.

Ok, you’re saying that high octane fuels may be [spark-] detonated at the compression ratio for that engine, whatever it is? No requirement to meet the highest threshold of compression that the fuel can accept before detonation?

 

[jviss]

Ok, you’re saying that high octane fuels may be [spark-] detonated at the compression ratio for that engine, whatever it is? No requirement to meet the highest threshold of compression that the fuel can accept before detonation?

That's a convoluted way of stating it, but essentially correct. I think you should say ignited since detonation has a pathological connotation in engines.

 

[Kings Gambit]

That's a convoluted way of stating it, but essentially correct. I think you should say ignited since detonation has a pathological connotation in engines.

Ok. But you introduced the word detonation, not I.

 

[jviss]

Ok. But you introduced the word detonation, not I.

Yes, and I think I used it correctly. Detonation occurs when, during the combustion cycle, after the spark plug has ignited the mixture, a new flame front is produced by the heat of compression, and the spark-plug ignited front and this second front meet. It can be particularly deleterious to the engine if this happens before the piston reaches TDC, i.e., you can blow a hole in the piston. So, higher octane fuels are formulated to suppress this tendency for heat and compression induced ignition and the resultant detonation.

 

[hawk232]

"Detonation" as often referred to in the internal combustion engine occurs whenever the "explosion" in the cylinder occurs before the piston is at top dead center. This is a function of fuel quality, octane, compression ratio and timing. As mentioned, detonation will eat pistons.

If the mixture combusts prior to ignition, this is referred to as "dieseling". This is a function of engine temperature, fuel quality/octane and compression. (a "dieseling" engine will try to continue running even after ignition as stopped ie the engine as been turned off). Dieseling is not typically as bad as detonation since full compression is typically required which means that by the time combustion as occured, the piston will be past TDC.

Higher octane fuel has a more controlled, less volatile burn than lower octane fuels. Because of this you can run higher compression or higher timing (sometimes both). All of this is in an attempt to try to get the "explosion" (in the cylinder) to occur just as the crankshaft moves the rod to the down side of the compression stroke.
,
saying that higher octane fuels wont cause harm is technically true, however it is also typically used when talking about 87,89 and 93. 100 octane will have an even slower burn than 93 would so the "explosion", theoretically, would be delayed some therefore, costing you some power (and efficiency). (the piston will be further along the stroke when the mixture combusts.)