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Catalina/Capri 25/250 Sailor's Forums

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O/B engine question:

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AADIVER
Admiral

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USA
966 Posts

Initially Posted - 08/04/2008 : 11:22:37

When running the engine for flushing, should the gas line be disconneted and the engine run 'til it's out of gas, or should the gas line stay connected, flush for a set amount of time, and allow gas to stay in the engine? I'm getting conflicting advice. Thanks.

Frank Farmer
Long Beach, CA
aa.diver@verizon.net
http://mysite.verizon.net/aa.diver

PRETTY PENNY
'01 C-250 WK, Hull #558

Edited by - on

tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 08/04/2008 : 12:09:00

Frank as always there are more than one way to "flush it".

My previous motor was a Johnson 9.9 OB. Bought new in 1992 and never flushed until retirement in 2005, being run in salt water only.

My current motor a 2005 Nissan/Tohatsu 9.8 is flushed once a year when pulled for the season at which point it is placed in a tub of fresh water in the shed and run for approximately thirty minutes. During this winterization I also fog oil the cylinders and for the last few minutes run the gas out of the motor. Lastly I drain the lower unit and refill with the appropriate weight oil and drain the motor sump and refill with Castrol 10W30 motor oil.

In the spring I once again place the motor in a tub of fresh water and run it to make sure all is as it should be and then it is back on the boat. So far so good.

Val on Calista,# 3936, Patchogue, N.Y.

Edited by - on

AADIVER
Admiral

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USA
966 Posts

Response Posted - 08/04/2008 : 12:47:55

Val, are you suggesting that flushing the engine after every use is unnecessary; that corrosive salt buildup occurs very slowly? And when flushing, what's your opinion re draining the gas out or leaving it in?

Edited by - on

JohnP
Master Marine Consultant

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1520 Posts

Response Posted - 08/04/2008 : 13:11:54

I have read that running an O/B only once a week causes the gas to partially evaporate and leave residue on the internal surfaces, so I almost always pull the gas line off the O/B about 100-200 yards from my slip and motor in. It takes about 5 minutes or more to run out of gas and stall, and I like the idea of keeping the motor free of gunk.

Haven't set up a water flush system yet. Good winter project.

Edited by - on

Breezy Cat
1st Mate

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38 Posts

Response Posted - 08/04/2008 : 13:15:59

I hope you don't mind if I add another O/B question to this thread.
How do you measure the "shaft" length?
My 85 Sea Monster is approaching it's end and the length is good but I can't tell if it's 20" or 25".
TIA

Edited by - on

dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 08/04/2008 : 13:28:25

Shaft length is generally measured from the transom (i.e. inside mounting bracket where the transom would be) to the cavitation plate.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/04/2008 : 13:53:00

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dmpilc
 Shaft length is generally measured from the transom (i.e. inside mounting bracket where the transom would be) to the cavitation plate.
<hr height="1" noshade id="quote"></blockquote id="quote">On many outboards, that measurement will be 2" to 2.75" longer than the specification, which is often called "transom height." Thus, a 25" (XL) Honda measures 27.75", and the 20" (L) measures about 22.5".

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/04/2008 : 14:00:12

Oh... about running dry... The Honda mechanic here tells me to:
1. Treat every tank of E-10 gas with stabilizer (and some Startron for good measure). I use the new Marine StaBil--the green stuff.
2. Leave gas in the carb--the treated gas is supposedly less likely to create varnish and gum than the residue from running it "dry".

That's what I was told. I left thoroughly treated gas in my Honda 2 carb all winter and it started on the first pull this spring. Startled me!

Edited by - on

Breezy Cat
1st Mate

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38 Posts

Response Posted - 08/04/2008 : 14:19:32

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dmpilc
 Shaft length is generally measured from the transom (i.e. inside mounting bracket where the transom would be) to the cavitation plate.
<hr height="1" noshade id="quote"></blockquote id="quote">

So I would measure from the top of the motor mount where the engine clamps rest to the first cavitation plate?
That's a longer measurement than I thought.
Thanks

Edited by - on

AADIVER
Admiral

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USA
966 Posts

Response Posted - 08/04/2008 : 14:58:26

According to the Tohatsu Guru on the Marine Engines website:

"Always run an outboard dry when you are done using it. It does not hurt the engine(if it is healthy) and prevents the number one cause of outboard problems...Carburetor issues."

And from the "horse's mouth" (Nissan/Tohatsu):

"Flush after every use, and only run it dry is you're not using it for a month or so, regardless of additives."

Edited by - AADIVER on 08/04/2008 15:08:47

Ray Seitz
Captain

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USA
416 Posts

Response Posted - 08/04/2008 : 19:59:22

I was advised to always use stabilizer because fuel manufactured today is not made with any shelf life. I took that to mean the refiners don't add stabilizers anymore. I have never, in the seven years I have had the Honda, ran it dry after use. Heck half the time I don't run the motor for the 7 or so minutes it takes to run it dry. In the fall I drain the bowl after fogging. No need to flush in fresh water.

Is there?

Edited by - on

Even Chance
Captain

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USA
393 Posts

Response Posted - 08/04/2008 : 21:13:46

Interesting, Dave. My Honda mechanic told me last year during the orientation to my new 9.9 to pull the gas line and run it dry every time.

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Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 08/04/2008 : 22:09:20

Frank,
I don't think there is a right or wrong answer to this question. If I know I will be running my engine within two weeks I leave gas in the carb. If I know it will be more than two weeks I run it dry. If in doubt I do not run it dry. But that's just me.

Edited by - Sloop Smitten on 08/04/2008 22:09:59

OLarryR
Master Marine Consultant

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USA
3410 Posts

Response Posted - 08/05/2008 : 05:50:09

I use my outboard all year and I have my sailboat on the Potomac River (freshwater). I do not flush the outboard at all. Maybe I should...but I don't. However, when I lived on Long Island and sailed for many years, first on the south shore and then in the Long Island Sound, I did do annual flushing. (Seawater)

In regards to your question, you did not indicate if you are just flushing mid-season or the question is in regards to end of season flushing. If in mid-season, i see no reason how the running the gas out or left in is in anyway connected to the flushing operation. I figure that is understood but what the heck, I would mention it anyway. the question then becomes, if the flushing is at the end of the season or at a period when the outboard may not be used for a period of time, then should the gas be run out of the outboard. I recall this discussion awhile ago since I use my outboard probably 2-3 times a week and was always running the gas out each time. I have now stopped that practice since others mentioned that there was a greate rchance if running the gas out, that water/moisture could set up in the gas line. So, I now shut the outboard as soon as I dock (sometimes...even a few seconds before I dock). I see no effect on the outboard's performance.

I do use either stabil or what I have been using for now more than a year is Startron which inhibits water formation and breakdown of the gas. I add it to every fill up of the outboard gas tank. I do same with stabil for just the end of season for my lawnmower and pressure washer. So...especially at end of the season for the outboard, I would run the gas out but ensure either stabil or startron is used at least then, if not a habit using it on a regularl basis.

Edited by - OLarryR on 08/05/2008 05:52:23

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 08/05/2008 : 07:29:48

Usually no need to flush in fresh water Ray. I've flushed and run the gas dry with my engines all my life. Have never used any additives and had excellent performance and long (20-30 yrs) lives with my motors. That being said I've always had 2 cycle engines until my Suzuki 2.5. I think if you're mixing gas and may not use your motor for a month, run it dry, but a four stroke is fine without running it dry. If you're in fresh water, no need to flush. Of course there's always exceptions. If you're in a area where there's a lot of lime in the fresh water, you might want to flush occasionally.

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 08/05/2008 : 08:06:53

As to running the fuel dry after each use, one would think this would be a fairly important bit of information that outboard manufacturers would pass along to their customers, but I've never seen it any outboard manual. For long term storage or transport, they will mention draining the bowl by opening the bowl drain screw, but nothing regarding running the engine until dry.

For those who run it dry, do you also run the fuel dry after each use in your lawnmowers, leaf blowers, weedwackers, edgers, generators, snowblowers, cars, or any other gas powered device?

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 08/05/2008 : 09:13:47

My lawnmower is a 4 stroke, so I don't mix oil in the fuel. My weed whacker has a bulb to push more gas into the chamber which would dilute any residual oil. The issue in the past has been, with the 2 cycle engines, oil on the plugs causing them to foul. I had the same problem with motorcycles. We would keep extra plugs on the bike to switch out if one became fouled. They were easy to get to on a bike.

I disconnect the fuel line near the end of use on 9hp to a 40hp and let the engine run till it shuts off. The engines have been running well for over 30 years with this technique.

Before I started "running them dry" I would have a hard time starting the engines and they would often have one plug not firing.

Now I have a 225 evinrude oceanpro engine and I don't run it till dry just because it spits out so much smoke and makes so much noise. I only use the boat every other month. When I first get to the boat I often remove each plug and clean them and spray starter fluid directly into each cylinder just before replacing the plug. Starts up and runs fine. If I don't clean the plugs the engine is hard to start and skips until it gets warmed up. I'm sure I need new plugs and wires.

This boat in in freshwater now, but when I used it in saltwater I would always hook up a freshwater hose to the engine and run it after each use, as it was a trailered boat for a while.

These are all older engines (1980s and earlier )

I have no idea what people are doing on the 4 strokes and newer 2 stroke engines.

Edited by - on

jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 08/05/2008 : 23:05:18

My new Merc also advises to pull the fuel line and run it dry.

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