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Pete McCrary

Tohatsu 3.5 hp longshaft . .

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Some may know that the Suzuki 2.5 cavitated excessively as "Chessie's'" OBM on her maiden voyage [empty ballast tank & solo crew].  So I replaced the OBM with a Tohatsu 3.5 hp longshaft which was hard to start, wouldn't idle properly, and ran poorly and was generally unreliable to the point that I didn't dare join in the water events at the MASCF.  We think the selling dealer's mechanic has discovered the problem.  A small hole in the fuel pump's diaphragm.

 

The pump gets its energy from the negative pressure in the intake side of the carborator-- which [hole] allows some extra gas to enrich the mixture beyond what it should be causing unburnt fuel to exit thru the exhaust and generally poor running.  This diagnosis will be confirmed after installing a new fuel pump.  A trial run on the water will be proof.  The mechanic says that some OBMs power the fuel pump with exhaust pressure -- which wouldn't have any effect on the mixture, but [probably] would cause other problems.

 

Has anyone else had a similar problem with a new small OBM?  

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I'm all ears.  Anxiously waiting for your report.  My 3.5 is cranky as heck.  It's been "ok" with a new carb, but still has a flat spot when accelerating. Using nothing but Truefuel now.  

 

 

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All engines have application specific issues. Known weak or poorly designed parts. Find a real Suzuki mechanic and have them look up the common idiosyncrasies. Again ALL engines have them and the good mechanics, know what they are and likely how to best address them.

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I noticed you had the Suzuki back on board at the messabout and meant to ask.  Suzuki seemed to do ok? 

 

I know it's a different issue, but my Suzuki ran almost like a different engine after I ran it through the first gallon or so, i.e., after it was broken in.  The manual advised a break-in period, but I was surprised at the difference it made.   After that initial period, it now idles like it should, including running at low speed to allow shifting without a big thump.  Also starts reliably and predictably, like it should, without undo fussing back and forth with choke and throttle.  Basically a one-pull engine now.  So, maybe after you get your new fuel pump on the Tohatsu, then get a chance to run it for a few hours, everything and everyone will be happy.

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The Suzuki ran just fine at the Messabout.  Turns out that both engines suffered from some bad gas (water!).  Wanting to avoid the ethanol problems, I bought several gallons of ethanol-free 93 octagon gas from a Steil dealer.  At the MASCF when the Tohatsu wouldn't run right, I took it to a marina mechanic [who] discovered water in the gas.  But he still couldn't get it to run properly.  It took the dealer to find the hole in the fuel pump diaphragm.  So, I got rid of all the ethanol-free gas and am now using regulars gas with a stabilizer additive.  That made the Suzuki run like a charm.  Also, its short shaft didn't cause any cavitation -- maybe because I always had the ballast tank full and at least a crew of two adults (myself included).  In that configuration the hull speed was almost 5 knots.  If there is little or no cavitation when I'm solo with full BT, then I'll keep the Suzuki and sell the Tohatsu.

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We rent out a couple skiffs with 9.9s on them at work.  My first 2 years we had constant problems with fuel. It was always the fuel.

 

If you can get ethanol free, do so!  If not, treat it with something that combats the absorption of moisture.  Don't store more fuel than you can use in a short time.  I will pour month old fuel into my truck so I can get new. What ever it takes, be anal about fuel.

I never had to deal with laying an outboard down between uses.  Apparently that is another issue.

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Fuel stabilizers work, get some. I have lots of small gas engines, all run the same fuel, which is jug stored with a stabilizer. 

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I'm fortunate to get non-ethanol gas at the yacht club, where we have it in the fuel pump specifically for the marine engines in use there.  It does seem to make a difference.  I know I'm tempting fate, but I put some stabilizer in last fall (both in the fuel tank and ran it through the engine when I ran the engine dry) and everything worked this spring.  Fingers crossed.

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I've used stabilized fuel that was over a year in storage and had no issues. You don't need to purchase non-ethanol fuels or worse the old leaded stuff, which is also still available and not desirable on modern engines. In marine applications not as much of a problem, but will screw your O2 sensors and catalytic converter in a car. Once stabilized the fuel isn't hygroscopic any more and it ties the few other additives together a lot longer, so corrosion isn't an issue. The real problem with ethanol laced fuel is the break down of the additives in the presence of moisture, which eats stuff, like gaskets and seals, plus the corrosion.

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I bought my ethanol-free 93 octagon fuel from a Steil dealer whose customer base is mostly rural.  Their tank is above ground and about 500 gallons in size.  It turned out to be contaminated with water.  That can happen if you happen to be getting your fuel load from near the bottom of the tank.  Especially if the dealer has a fairly low sales volume of that gas.  The tank can be half empty for multiple cycles of temperature & humidity variations -- causing condensation.  And the tank was not under cover, which would exacerbate the temperature daily highs and lows.  I got rid of all the e-free gas that I had.

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For several years now, I've run my 2.5 hp 4 stroke 'Zuki with non ethanol fuel and Sta-bil. I always have some left in my gas can that sits over winter. I use it in my outboards as well as other small engines. Since doing this, I've had no fuel related problems. I buy the gas from a station that seems to have a fairly high turnover, so the gas doesn't have problems with water, or sits in the underground tank too long.

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I'm with Chick. I have had good luck with this web site https://www.pure-gas.org/

 

I also would add that on my Honda 2, there is a little drain screw on the fuel bowl that gets the last half teaspoon of gas out after you run it dry, which I do for really long term storage. I think draining the gas by running it out and then leaving that little bit is not good without getting rid of this. I haven't checked my Suzuki to see if it has such a drain.

 

I have a few old motorcycles, antique tractors, chain saw, weed wacker, etc. One thing overlooked which can wreak havoc on these small machines when not used is insects. Make sure when you store them they are out of the way of mud daubers and the like. A tiny passage is all they are looking for. I have resurrected more machines that suffer from this. I keep all of mine in a garage with a tight fitting door and they still find a way in. Just this summer I had a Stihl 2-cycle weedwacker that wouldn't start and it had spark, gas, etc. I took that tiny carb off and it was clean. I put in a new diaphram and it still wouldn't even fire. It was then that I grabbed an air hose and blew a big bunch of mud out of the exhaust port (mud dauber nest or something) and she ran perfect.

 

On my little Honda I have a cover for that I shoot with bug spray, let dry and then put on. I had the vent for the float bowl get plugged once this exact way. 

 

A friend says stress can be measured by how many internal combustion engines you own.

 

 

 

 

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I only use non-ethanol fuel in all my small engines.  It is just not worth messing with.

 

And after the break-in period, my little ‘zuki runs like a top.

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Tohatsu 3.5 proof of repair cruise.

 

The motor started just fine and ran like a "top."  And restarted without any problem.  The fuel pump was replaced under warranty at no charge for labor.  We cruised from Leesylvania State Park (Virginia) up The Patomac River to Gunston Cove -- about 12 nm (24 RT).  Speed at about 4.5 to 5 knots at ~ 3500 rpm.  Used 2.4 liters.  An enjoyable day, temps 50 to 60 degrees.  Calm in the am, about 8 knots in the afternoon.  I now have confidence in this motor and hope to be cruising "Chessie" early next year.

 

We saw several eagles.

image.jpeg.0f23c487da82d0c118d4058b16e541ac.jpeg

 

Brenda, my occasional helper and crew at the helm.

image.thumb.jpeg.a93f1b6fddc7a0b841592cd409e4c3a4.jpeg

 

Chessie, resting for lunch.image.thumb.jpeg.7e849d77fc24e0cbb9522aea5d41422a.jpeg

 

Brenda taking a brake in the easy chair.

image.thumb.jpeg.684b880cfc3cd6e6def163d30a96e0c6.jpeg

 

The old man at the helm.

image.thumb.jpeg.bd4366424f49fd95940d152b4c7adf2e.jpeg

 

Chessie is now in the garage waiting for her electrical systems.

 

 

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Glad to hear of your success.  My motor has had similar symptoms, but is not on the recall list.  I am going to go ahead and replace the pump as it is only $35, as it is not brain surgery.  Cheaper than driving up to the shop and back.  Time is money.  

 

 

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The selling dealer was Cabelas Sporting goods.  Very busy with only one guy as mechanic, parts man, and shop foreman.  And they had at least 3 salesmen pestering him to prep their sold-boats and ATVs for delivery.  When I told them of my motor problems they should have known, considering the recall, the cause right off.  It took them two weeks to figure it out, and then another two weeks of not even ordering the replacement pump.  I took back the motor and another dealer (Backyard Boats in Woodbridge, VA) got it all done pronto.

 

Right from the beginning, the motor was hard to start and really hard to restart.  But once it got going, it seemed to run ok.  But after three trips on the water (total running time about 3 hrs) -- it just wouldn't idle and was spitting oily or unburnt gas with the exhaust.  Clearly, symptoms of fuel pump problems if you really knew the engine and its characteristics.  I think the fuel pump diaphragm probably had a very small crack in it (at the start), and it rapidly got worse with use.  Now it runs like the other outboards that I've had.

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