FWC Outboard !

[Occams Razor]

Hello All !

I had this idea kicking around in my head of FWC a outboard. Well a tinkering buddy that loves to Mod big Mercs asked me to
give him my ideas. I did and I will be damed it works ! A racing 2.5 Merc was moded to use its raw pump to force water through the heat exchanger. We used a high speed electric pump to circulate the fresh water through the powerhead. Several additions had to be made to keep the fresh in the power head and use raw to flush the exhuast (this engine does not exhuast through the prop). Well long strory short full throttle and it had plenty of cooling. Looked like a nasty contraption but it worked. I'm wondering if anyone has thought of this idea for the 4 cycle outboards ? My thoughts would be to double stack the water pumps ( one raw one fresh) both driven by the shaft, use a tuned Y to provide raw water to the heat exchanger on exaust and then the other pump to circulate the fresh from the powerhead to the exchanger and small exspansion tank. I think Honda should consider this idea ! They have the tech to do it easily and we would not have to worry out block errosion in the powerhead and gasket failures for years and years ! Replace the exhuast manifolds when they let go but the powerhead itself would still be pristine with nice clean ethy-glycol in the block. Maybe if we all ask they will build it !

Oh buy the way the 2.5 Merc was a blown up engine that he had the weld the block back together so its just a experimental powerplant. We did not ruin a new 2.5 Merc. Just wanted to add that , I know there are some Merc lovers out there.

[welder]

We have to be careful not exhausting through the prop, If the government finds out we can do that they will have us running Catalytic converters even sooner.

[Occams Razor]

Welder:

Buddy its coming anyway so you better get used to the idea. Actually I hate the through prop exhaust myself. It cause the gear housing to be excessively large and disrupt water flow and the exhaust can heat up the gear oil pretty good too, that is why I only use synthetic as do most big block outboards.


I was thinking a stainless heat exchanger in the rear transom on a Pacific......
All good ideas......

[MacCTD]

Interesting idea but I think they have advanced corrosion protection enough that it is really not an issue anymore. I would imagine there are some benefits to being able to run at a steady temp but they seem to have that worked out as well, I think it would add another layer of complexity to outboards without any significant benefit.

[Occams Razor]

Hello All !

Yes minor complexity will be added to the cooling system in a FWC, however the benefits would be greater than the exspenditure. First of all there is the Corrosion problems that could be greatly improved upon. Second the engine emisions could be controlled better if the engine were kept in a certain optimal temp range. Third engine performance and longevity
could be greatly helped with a constant temp range preventing the exspansion and quencing effects outboards go trough during a normal day. This up and down temp greatly reduces gasket life no matter how good the design, especially in aluminum block designs. The european engine designers discovered this a long time ago, that is why their aluminum engine tech has led in design for years. The american engine people were secured to iron and steel ( better in many ways ) but too heavy. I could go on and on but it would be a great benefit and it can be done without complete redesign. In todays big block double overhead cam 4 cycle wonder outboards that cost 20 grand or more 30+ for the 350s, I think it should be at least an option.

[oldflathead]

I have been making this modification on the "old flatheads", (inboard Universal Atomic Fours, built from 1946 to 1978) for several years. I add an additional water pump for raw water and use the original pump to recirculate coolant. You will need an adequate sized heat exchanger and expansion tank, plus some plumbing parts. It adds about $1,000 to the price of the A4, but allows the engine to run at optimum temp, which is more economical, reduces acid build up in the oil and the engine does not corrode internally.
Installing the extra water pump and heat exchanger under an outboard's cowling will be a challenge.

Tom