Outboard motors; Cruising, dingy, tips, maint, & reviews

[s/v Faith]

In the thread on the Folkboat Frank offered the following good advise on outboards;

Many OB's with proper use go what seems like forever.

  I have a lil 2hp dingy engine I bought new in 1983...still starts 1st pull...ya can win bets with it. An OB requires minimal maintenance BUT you gotta use your head.

  Do NOT run them with the water pick-up out of the water...the lil impeller will pack it in VERY quickly that way. Even a 'bit' will usually start the premature wear. No water-no cooling-no engine.

  The carb MUST be kept clean. A 2stroke OB left sitting with old gas in the carb will build up a greenish 'varnish' residue in the main and pilot jets. The more it builds... the smaller the hole in these jets become...too small and the engine will run lean and eventually burn a hole in the top of the piston. REAL simple. run it out of gas before storing or loosen off the nut on the bottom of the float bowl to drain it....

   OB's used right, if not oversized will give good/long service and be economical at a fraction of the cost of a diesel and free up storage space too. Really depends how/where you intend to use your boat

_{(bold added)}

  Most weekends someone will show up at the marina with a boat that won't start.  many, if not most of the problems usually are related to contamination in the carburetors / fuel delivery system. Something that would be easily prevented by following Frank's advise above.
 

 

 

[s/v Faith]

  2 stroke outboards like RPM's, and do not like to idle long.  The plugs will load up, as well as the exhaust ports.  I see overpowered sailboats alot, the Catalina 22' with the 9.9hp outboard is carrying about 2x the horsepower then it needs. 

  There is a calculator for horsepower, that can help you figure it out but the 5' rule works out pretty well; 1 hp for each 5 feet of LOA (round up).  My nearly 4 ton (loaded) Ariel moves well with my 6hp 2 stroke.  I can operate through the throttle range, but find there is a point slightly past half throttle where my hull speed is about 5.25knots, and my fuel last much longer then 'wide open'.

  When I delivered Ariel Spirit, I found that the 9.9hp Merc was too much for the boat.  It would squat when the throttle was turned, and the bow wake would just get bigger without gaining any speed over ground when the throttle was turned further.


   

[s/v Faith]

Another problem I have come across often is with fuel.

  Old gas can cause quite a few problems with any motor, but especially four stroke motors.  Years ago I worked in a motorcycle shop.  The tech rep gave a short course on fuels.  Gasoline ought to be sold with an expiration date, since it breaks down so quickly.  The vented plastic tanks we keep it in aboard the boat, with rapid temperature changes and high levels of moisture is about the worst environment.

  I have a 13 gallon tank that came with the boat.  I removed it, and use a smaller tank unless I need to carry that much fuel. 

  2 stroke motors are vulnerable on a couple fronts.  The oil you mix with the gas breaks down as the fuel ages.   According to the Yamaha tech rep, gas mixed as recently as 4 months ago might already be losing it's ability to lubricate the engine.  Scary when the 100:1 mixes introduced to lessen environmental impact are already marginal in providing lubrication for your outboard. 

[Captain Smollett]

Yep, in the their tech manual, Johnson states clearly that fuel older than ONE MONTH is of suspect quality and should be discarded.  IMO, this poses a very real problem for sailors.

When keeping my boat our the Wateree Sailing Club, I would often buy about 3 gallon of gasoline a year; Even if I motored out of the cove or back (I sailed when I could, that is if there was ANY wind and I had the time), that 3 gallons lasted me a year.  I've been known to go out with less than a pint, and even with too little to start the engine (remember, it is a SAILBOAT FIRST :) ).

Now that I am using my boat in a coastal environment more and more, and I usually have my family with me, I leave the dock with a full tank - 6 gallons.  Last time to Winyah Bay I ended up motoring about 15 miles and used less than two gallons of fuel.  Technically, according to Johnson, my remaining 4 gallons is now spoiled.  I find myself wanting to go out and be a motorboat more just to use up the fuel without wasting it, and having an empty tank for the coast so I know while we are "out" the fuel is clean and fresh.

Of course, most of this would apply to an inboard gaoline engine (like th e A4), also, except I *think* with inboard tanks and fuel lines, maybe you don't absorb QUITE as much water and don't lose QUITE as much of the low boiling volatiles.

[AdriftAtSea]

Also, the problem has gotten worse, with the addition of Ethanol in the place of MTBE.  Ethanol allows gasoline to absorb water...once the ethanol has absorbed enough water, it no longer serves as an octane booster, which is its primary function in modern gasollines. 

The older MTBE-based gasolines were good for up to sixty days, in a marine environment.  The newer ethanol-based gasolines have a much shorter lifespan.

[Captain Smollett]

I did not think the purpose of ethanol was as an octane booster, but rather to reduce NOx emissions in the exhaust.  Of course, as Larry Anderson of UC-Denver showed back in the early 90's, adding ethanol increases oxygenated radical pollutants like CHO and C2H5O, which are in some ways far worse to have in the breatable air.

In either case, I agree 100% that ethanol in the gasoline makes the water absorption problem worse.  Also, some older outboards use seals in the fuel system (including inside the carbs) are incompatible with ethanol.  I *think* modern rebuild kits for these older carbs include ethanol "friendly" components.

I avoid ethonal containing fuels when at all possible.

[s/v Faith]

I am  not sure if ethanol is used as an octane booster, but you are correct that it is not a good fuel in a marine environment.

 The alcohol attacks the rubber in the fuel delivery system, and on a 2 stroke it can also affect the reed valve seats.  It does absorb moisture at a higher rate as well.

 I would not recommend running ethanol in any motor unless it was specifically mentioned in the owners manual.  .

[s/v Faith]

Sorry, I hit reply while you were typing.  Seems like we had the same thing to say anyway....  ;D

[AdriftAtSea]

The reason adding ethanol reduces NOx emissions is that it acts as a oxygenator for the fuel, since it has an -OH group, being an alcohol. 

Higher concentrations of ethanol, like E20 gasoline, often result in higher engine temperatures, and that leads to engine damage.

(Edit, Captain Smollett: corrected typo)

[oded kishony]

>I would not recommend running ethanol in any motor unless it was specifically mentioned in the owners manual.  .<

All the fuel lines on my week whacker completly dissolved due (I think) to ethanol in the fuel.

I add something called 'gas stabelizer' to the fuel on a roto tiller (8HP). Claims to prevent fuel breakdown in storage.  I wonder if this would help on a 4cycle outboard? How about on 2 cycle?

Oded

[AdriftAtSea]

I did not think the purpose of ethanol was as an octane booster, but rather to reduce NOx emissions in the exhaust.  Of course, as Larry Anderson of UC-Denver showed back in the early 90's, adding ethanol increases oxygenated radical pollutants like CHO and C2H5O, which are in some ways far worse to have in the breatable air.

In either case, I agree 100% that ethanol in the gasoline makes the water absorption problem worse.  Also, some older outboards use seals in the fuel system (including inside the carbs) are incompatible with ethanol.  I *think* modern rebuild kits for these older carbs include ethanol "friendly" components.

I avoid ethonal containing fuels when at all possible.

Actually, it's primary purpose is octane boosting, as ethanol has a native octane rating of 129.  MTBE, which is what ethanol is replacing, is also an octane booster, and both ethanol and MTBE were replacing the original octane booster used in gasoline, tetra-ethyl lead.   You can read a bit about ethanol's use here:  http://www1.eere.energy.gov/biomass/ethanol.html

[Captain Smollett]

We are both "right."   ;)

EPA Web Site "MTBE in Fuels"

Why is it used?

MTBE has been used in U.S. gasoline at low levels since 1979 to replace lead as an octane enhancer (helps prevent the engine from "knocking"). Since 1992, MTBE has been used at higher concentrations in some gasoline to fulfill the oxygenate requirements set by Congress in the 1990 Clean Air Act Amendments. (A few cities, such as Denver, used oxygenates (MTBE) at higher concentrations during the wintertime in the late 1980's.)

And a similar comment applies to ethanol.  Contemporary consumer engines "like" fuel octanes in the low nineties, and adding more "octane booster" than is necessary to reduce knocking (cylinder detonation) is actually not good for the engine either.

Note that Denver is specifically mentioned in this EPA blurb.  I was at UC-Denver in 1993-1994 teaching chemistry at the same department as Larry Anderson when his research showed, very conclusively, that the presence of these oxygenated compounds in fuels causes some pollutants that are actually far worse than NOx emissions.  Many places have ethanol concentration caps to help keep these pollutants in check.

[Fortis]

My contribution on outboard being used to drive sailboats is; Look into getting a yacht prop. Most outboards are fitted with props for planing hulls when bought. Retrofitting a yachtprop provides more torque and efficiency at pushing the heavier boats.

Having helped a frind convert his 8hp Johnson 2stroke on his E26, the difference before and after is amazing.
All that futile egg-beating struggle ceased and the boat moved with far more certainty against waves. Basically , it came much closer to feeling like my inboard with the big three bladed feathering prop. Lots of grunt when you need it, less noise and churning water that is already too riled to provide much push.


Alex.
P.S yachtprops are available for just about any outboard brand in any size over 4.5hp.

[s/v Faith]

My contribution on outboard being used to drive sailboats is; Look into getting a yacht prop. Most outboards are fitted with props for planing hulls when bought. Retrofitting a yachtprop provides more torque and efficiency at pushing the heavier boats.

Having helped a frind convert his 8hp Johnson 2stroke on his E26, the difference before and after is amazing.
All that futile egg-beating struggle ceased and the boat moved with far more certainty against waves. Basically , it came much closer to feeling like my inboard with the big three bladed feathering prop. Lots of grunt when you need it, less noise and churning water that is already too riled to provide much push.


Alex.
P.S yachtprops are available for just about any outboard brand in any size over 4.5hp.

  Good post Alex,

I changed the prop on a Yamaha on a Grampian in my marina.  The lower pitched prop made it run much better in fwd, but it was a completely differnt boat to back.  it would have been worth the price fo rthe excahnge if only for the improvement in backing.

[AdriftAtSea]

Yes, most props on outboards are designed for powerboats, and changing to a prop that is sized and pitched for your boat is a huge help.  I personally like the new composite props, since Buzzards Bay has some shallow areas, where you can ding a prop...and on a composite, you can replace individual blades.

[Captain Smollett]

Improved performance forward?  MUCH improved performance in reverse?

Okay, I am definitely interested.  Can anyone suggest a vendor to reprop my 1979 6 HP Johnson "Work Horse"?

[Seadogg]

Here, here!

I have the same beastie--just under the Evinrude moniker. Would be quite interested in this info.

Nick

[s/v Faith]

I would recommend writing down the model number and contacting the Johnson / Evenrude dealer.  I would expect they can look it up and see if an alternative prop was offered.
You might have to remove your prop and take it in with you to verify that you do not already have the correct one installed.

 

Yamaha calls theirs the 'high thrust' prop, and there is also a 'high thrust' outboard offered with a different reduction in the lower unit.  Some manufactures might label theirs as 'speed props' or 'torque props' or maybe by the displacement/non-displacement.  I am sure the dealer will be able to give you more info (if a new prop for a 1979 motor is still available).


  The only problem we encountered was that the dealer was not willing to let us 'try it out' so it was a gamble.  The prop was ...($220?) so it was a bit of a risk but worth it in this case.

  Good luck!



OBTW, in case anyone does not already have the option installed many manufactures offer 'rectifer' charging as an add on for their outboards.  Most electric start motors will already have the charging options which is nothing more then a pick up that you bolt onto the powerhead next to the fly wheel.  This option was rarely standard on a pull start outboard, but can usually be added with very little effort.

  I had one on the Suzuki 8 that I traded to Bill, and have one on my Yahaha 6hp that was added on.  It is rated at 10 amp max output, and does a nice job of toping off the batteries when motoring.  I have gone without charging for as much as 8 days and maintained the batteries without running the motor much.  One thing to be careful of is that the rectifier is not very good at regulation, and it is a god idea to keep an eye on the voltage.  Mine has climbed as high as 18 v  :o when I have motored for a while, not so good for the electronics but easily prevented with a charge controller, or a watchful eye on the voltage.



 
 

[AdriftAtSea]

Some of the smaller outboards would be well served by a composite prop, which are more efficient that the standard aluminum ones, and generally about the same price or a bit less, and safer for the lower unit in the case of a grounding or hitting a submerged object.   

The two primary manufacturers are Pirahna and ProPulse, both of which have a central hub and replaceable blades.  ProPulse makes an adjustable pitch prop, and Pirahna changes pitch via replacement blades.

I'm currently using a Pirahna on my outboard Honda 20 HP.  The 20 HP Honda four-stroke is also nice since it has a 12-amp alternator built-in.  (actually it may be a rectifier unit, rather than a full-fledged alternator).

[Fortis]

Ive never been a fan of composite props...But then again with 20hp of inboard deisel, my choice of a feathering stainless prop of doom makes sense anyway.

There is a three bladed featering prop made with composite blades available (and much cheaper then ours)...but I got to play with it at the boat show and think..."no, thank you".

It was several days later that it occured to me that given our prop shaft sits 60cm or more above the bottom edge of the keel and rudder, any grounding that snaps off a prop blade is probably already giving me a very bad day.

On a dinghy that we run right up on the beach and sometimes use to "discover" unexpected sand bars at night...a composit prop blade as the very bottom-most part of a boat seems a bad idea.


I am prepared to be convinced otherwise...

Alex.