OUTBOARD

[JOD]

I'm a new owner of a Bay Raider 20. Working my way through the forum I was a little concerned by posts referring to motors of 8and 9 hp. The manual recommends 2.5 and my boat has a Yamaha of that power. I've not been able to launch yet due to the carb being blocked by debris. I have been waiting over a week for apart from the Netherlands (so much for the benefits of speedy imports from EU membership). The service centre say that this is a common problem with small 4 strokes due to the very small fabrications. Any members have advice or experience to pass  on?

[Graham W]

JOD,

Welcome to the forum.

It all depends on where you’re going to sail.  2.5hp ought to be sufficient unless you’re somewhere with strong tidal flows or regularly have to motor against headwinds, in which case 4-6hp (they all weigh the same) might be better.  8-9hp is unnecessary. I have a Mariner 6hp with Saildrive propeller, which is more than enough for my needs.

Blocked carburettor misery is very common on small outboards, often caused by ethanol in supermarket petrol.  If you’re not going to use much fuel, I recommend Aspen distillate, which is three times more expensive but doesn’t seem to cause problems.  See http://www.swallowyachtsassociation.org/smf/index.php/topic,1377.0.html

[Sea Simon]

Graham W offers sound advice, which I would agree with on both counts.

Motor size - I have access to a Honda 2.3 and 5; the 5 is needed to get about with realistic boat loadings and wind/weather. The 2.3 is just enough, maybe if racing and want to keep weight down, or save your back when lifting it in/out of well. I routinely use the 5HP with a sail drive prop.
help here:
http://www.swallowyachtsassociation.org/smf/index.php/topic,1853.0.html

I have borrowed a Torqueedo, but having used it for a couple of weeks, was pleased I didn't buy it
Thread here
http://www.swallowyachtsassociation.org/smf/index.php/topic,264.0.html

Ethanol -  I too use ASPEN fuel, and this has provided the answer to my problems, at cost.
Also lots on the Drascombe forum about this. Consensus is cr@ppy (ie high ethanol, which attracts water and seems to be exceptionally good at blocking the tiny jets in the carbs of small 4-strokes) supermarket fuel does not suit small 4-strokes.

[Charles Scott]

I had 2 outboards, both of which became gummed up. I removed the carbs and took them to a local garage where they had an ultrasound bath, and cleaned all the jets ( charging the princely sum of £20). Both outboards now running and idling perfectly.
   I now run them as usual on ordinary petrol, but at the end of the day unplug the remote tank and run the engine to a stop, then run from the inbuilt tank which has Aspen petrol in it. So far so good, but only done this for the last year.
  Incidentally, I run my 4-stroke lawn mower on ordinary petrol, leaving the carb full of it season after season, and it starts and runs perfectly all the time!

[Sea Simon]

Charles,

Again, I do very similar to you. Aspen use is as limited as reasonably possible, but always when leaving the boat for an extended period.

Having been charged very considerably more than you (Marine engine dealer!) to have my old Tohatsu carb cleaned, I now have my own ultrasonic bath. Useful for all sorts of stuff (EBay £50 ish).
Has not been used in a season with my new Hondas, and Aspen fuel!

My garden machines (a mix of old 4 stroke mower, and newish Stihl 2-stroke stuff) run fine on the fuel rejected by my outboard.
"Professionals" tell me that this is because the clearances/tolerances in the newer outboards are VERY tight for the purposes of saving the planet; to meet emissions standards.
Apparently chain saws are ok?

[Graham W]

I think the constricted carburettor jets on small outboards have been devised with an eye on air and water pollution regulations, especially on inland waterways.  The fact that this also makes them unreliable at sea, where reliability is most needed, doesn’t seem to enter the equation.  Meanwhile large commercial vessels burn filthy sulphurous heavy fuel oil that visibly pollutes the air in shipping channels.

[JOD]

I now have the authoritative answer. Some of these issues have been mentioned by others but my service engineer, who certainly knows his stuff (working on road as well as marine engines) says as follows. Small marine engines have minuscule fuel passageways which can be blocked by the tiniest grain of dirt. This normally gets pushed out but can result in loss of flow and thus, power. It is this, not enzymes or water which is the problem. Although fuel can deteriorate, this does not cause problems for a small outboard because the quantities of fuel are so small; in the case of a 2.5 hp, around 2.5 litres plus 5 ltrs in the can. The answer is to throw away any fuel at the end of the season (put it in your lawn mower / car etc). Additives are a waste of money other than in static tanks and the associated piping. Even then problems will arise if clean operations are not maintained. As they are hard to clean they rarely are. What is important is scrupulous cleanliness. Marine engines are at risk because sand contains particularly fine but sharp gritty particles; much finer and harder than what is normally found in land based applications. It is hard to keep corrugated pouring nozzles clean inside so use a funnel, making sure it is cleaned throughout.

[Sea Simon]

...Meanwhile large commercial vessels burn filthy sulphurous heavy fuel oil that visibly pollutes the air in shipping channels.

Off topic I know, but...
Have to confess, shipping is my "bag" so to speak.
Things are changing for the better tho, and not before time; some of what went on in the past was scandalous.

See
http://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx

and

http://www.imo.org/en/MediaCentre/HotTopics/GHG/Documents/2020%20sulphur%20limit%20FAQ%202019.pdf

Northern Europe is an Emissions Control Area, but the far West of Cornwall is only just inside!

Hope this is of interest?