Looking for Advice: Replacing Outboard Motor on Hunter Formula One Sailboat

[Greenheart]

Very obscure question, but does anybody know how much noisier a modern 5/6hp is at (let's say) full revs, relative to the two-cyl 9.8 running at a rev-point that would crank out the same power as the smaller engine at WOT?

I may be wronging the smaller motors, I certainly don't know they're rougher - it just seems likely.

 

[Egret]

I'm suspecting an oldish 4 stroke 9.9 will be quieter and smoother as can hardly hear it when locker lid is down, but interested to hear from someone who has both types - as thinking of downsizing, but noise is a concern - also whether newest 6hp's of about 24kg weight are temperamental due to tiny jets as the 3.5hp seems to be.

 

[jamie N]

...... also whether newest 6hp's of about 24kg weight are temperamental due to tiny jets as the 3.5hp seems to be.

This brings around the recent conversation of "Outboard Woes", which quite rapidly descended into a playground spat of differing opinions concerning what actions should be taken at the end of the day when stopping the engine, and why they should be.
For me, to avoid any problems that blight these small jets, it's a matter of shutting down the engine in a certain way; turning off the fuel, or removing the fuel pipe, allowing the engine to stop on its own accord, and then draining the carb of what remains using the "carb drain screw". Doing these things has (I believe) helped in my having had no jetting issues with my 3 outboards.
Other opinions are available.
In short, I firmly believe that these small engines are absolutely reliable, as long as they're treated well with regards to modern E fuels.

 

[SeasickPete]

I'm suspecting an oldish 4 stroke 9.9 will be quieter and smoother as can hardly hear it when locker lid is down, but interested to hear from someone who has both types - as thinking of downsizing, but noise is a concern - also whether newest 6hp's of about 24kg weight are temperamental due to tiny jets as the 3.5hp seems to be.

I have had a 2001 mariner 4hp 4 stroke in the past and that always ran perfectly. Most issues arise from ethanol fuels so when I can I use Shell Vpower petrol as this contains none. Other then that don't use fuel over 6 months old and let the engine run the carb bowl dry as much as possible by disconnecting the fuel hose. Tohatsu now has a 6hp 2 cilinder model with fuel injection which completely removes any issues related to carbs from the equasion. It is heavier though at 38.5 kg.

 

[ridgy]

I'm going weigh my 6hp tohatsu tomorrow. The specs say 25kg but it feels much heavier than my weighed 20kg 2 stroke Yamaha.

I also sometimes drive a sailing club committee boat with a tohatsu 9.9 and both are pretty noisy at full chat. I think you'll be disappointed if hoping a 9.9 is significantly quieter. Just get an autopilot and sit inside.

One my other hobbies is fly fishing on reservoirs and those 4 to 6hp tohatsus are ubiquitous on all the hire boats and they get get thoroughly abused, do probably 2 hours a day in short (10 minutes) full throttle bursts 8 months per year and every one has worked perfectly for me.

 

[Concerto]

The original outboard was a 2 stroke tohatsu 4.5 HP long shaft with a separate tank. The Formula 1 is a very easily driven hull and provided the boat is not heavily loaded. When I raced her she was an almost bare boat with just a battery echo sounder, clip on battery nav lights, a small anchor, single burner on a gas bottle, a plastic bowl for a sink and an Elsan (never used). She was used as a day sailor and I never slept on her.

As new 2 strokes are no longer for sale in Europe, you have to have a 4 stroke. I would certainly say a 5 HP would be the maximum size. Having a separate fuel tank keeps the engine lighter to move. Whilst sailing the outboard was strapped in the aft locker and brought out only when needed. I never sailed with it on the transom as on starboard tack it would drag in the water and slow the boat speed. Most of the time we sailed on and off the fore and aft mooring, so the outboard was rarely used.

If you are considering a petrol engine, then use Aspen synthetic petrol as it has a much longer shelf life than regular petrol. It is used for engines that are used irregularly like chain saws, rotavators, lawn mowers, generators, small industrial plant, etc. It is more expensive but you will never use very much as a Formula 1 will usually sail well except a flat calm.

Hope these thoughts help in the decision on what outboard to buy.