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RL28 outboard exhaust fumes in engine well
does anyone have a simple solution to reduce the exhaust fumes from a 2 stroke engine in the well on RL28's to allow the engine to breath cleaner air. I have a few ideas but would appreciate the views from others who have had a similar problem. Regards Rob


Rob Ritchie12-Aug-2003    Edit    Delete 
exhause gases in the well
I had a Southcoast Magnum that had a four stroke Yamaha in its sealed well. The upper exhaust outlet had an optional hose connection that lead to a skin fitting on the stern ejecting most of the low speed exhaust. This was a Yamaha factory design.

I do not know what brand of outboard you have but it is essential to take the upper exhaust outlet out of the well to stop choking the engine at low speed. It is also helpfull to keep th hose sloping down away from the engine to avoid waterlocks that can be sucked back into the powerhead when the engine is turned off. Exhaust gasses are not such an issue at high speed due to the lower exhaust outlet shifting enough exhaust away from the well.

Use large diamater silicon hose available from purple pig or truck parts suppliers. Standard hoses may not take the heat of the exhaust.

Next, use Castrol Biolube 100 or a similar synthetic oil that also has the benefit of producing less smoke and less stink. I use 75:1 mix although Castrol recommend 100:1 (the oil has been tested at 200:1 in past tests). Its very good oil and you will not believe how much better your engine starts and runs at low speed. The oil is expensive but in the scheme of things its far more pleasant when leaning down to change gear. Whitworths sell the oil in 1 litre containers. Added bonus of the oil is it should keep the inside of the well cleaner than old fashion oils and of course the fish are happier.


Greg12-Aug-2003    Edit    Delete 
Exhaust Gases in an RL28 engine well - a breath of fresh air!
I think this discussion item may have solved a problem I have had with my 9.9 Yamaha 4 stroke in Jezabel. At low speed, even since new, the motor would sometimes run unevenly and then cut out - usually when manouvering in congested boat harbours - but would restart happily. The build-up of fumes in the engine well may be the cause. The engine runs perfectly most times, and I had suspected contaminated fuel or an intermittent electrical fault - both unlikely as the fuel is often refreshed and the motor not too old. Some other corroborating factors pointing to fumes in the well: 1) the poor running is only at low speed 2) often in boat harbours (still conditions with less wind and less movement to flush fumes) 3) the newer grey 9.9 Yamaha 4stroke is physically larger than the older 1990 white model giving less space for airflow around the motor [fitting this motor was a p.i.t.a. as most dimensions were not compatible with the older 9.9 Yamaha but that's a saga in itself!!!]

So thanks, Greg et al for your interesting comments - I may try an experiment to carefully / partially reduce the airflow into the well and see if I can reproduce the problem. If so, I can then plan to remedy it.

On another point - I'm a bit passionate that the motor be fed cooling water. The Yamaha tell-tale is virtually not visible when it's in the well. To help with flushing the motor ["Have the earmuffs fallen off yet?"], and to help detect any plastic bags wrapped around the skegg, I have extended the Yamaha rubber tell-tale pipe with a brass joiner and added another pipe and nipple. These emerge from the motor via the front rubber grommet. The (swivelling) tell-tale then pumps out into the cockpit, points straight up, or points into the well depending on what I want. The old 9.9 Yamaha provided the necessary "organs" for this extension.

Phil Gardam19-Aug-2003    Edit    Delete 

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