What are those little holes......

turbinedoctor

turbinedoctor

God
What are those little holes in the back of outboards below the power head section in the down shaft section used for. I hope I explained where I am talking about. They seem to let out exhaust, steam and water. Why are they there, what are they called and are they (one or both ) suppose to let water out. I have been noticing it when I run my motor on the muffs and cant find the answers I am looking for.

I dont have a picture of them, so if you know what I am talking about and have a picture would you post it please.


thanks, turbo
 
they are High RPM water bypass holes when you are running above 2500 to 3000 RPM's they pump the extra water out there to keep the power head from over heating. the exhaust and prop can't let out as much water as the water pump can put in at high rpms.
 
Is or should there be water comming out of both? I noticed mine only lets water out the starbord side when on the muffs. It seems to let some out at lower RPM's, but more like you said at higher RPM's.

Thanks for shedding some light on this for me.
 
I wouldn't be too concerned about when on the muffs. You can't deliver the same water volume from a garden hose that you do when the boat is in the water. That's why you shouldn't over rev your motor when on the muffs.
I had a 225 Evinrude on my Grady mounted on a bracket. I believe that the factory mounted the bracket a bit too low. Those exhaust ports were under water with the motor down and the motor didn't like to idle very long without dieing out unless I tilted the motor just enough for them to clear the water line. Then it idled fine.
On a side note, I forgot how clean my Yamaha was. :hi:
 
They are also an exhaust port. At idle most of your exhaust comes out of those holes. I've seen some Merc's tricked out with an almost "dry" exhaust using those holes. Makes 'em loud as hell.
 
Like stated above, they let the water flow out when the T-stats open up. And are also your primary exhaust outlet when the engine is idling in the water. This is the reason why MOST 2 stroke outboards idle real fast on muffs, and then come back down to normal in the water. 2 strokers are EXTREMELY sensitive to exhaust back pressure, espescially at idle. Just ask some hot rodders what happens when you open the exhaust on a 2 trsoke without adding fuel :cen:.
 
chumbucket said:
On a side note, I forgot how clean my Yamaha was. :hi:
Click to expand...

CB, WOW!!!, I just saw the pics of your ol' V for the first time... That was one sweet boat! You really kept that thing clean.

I wish I had been in the market when you sold it.

Anyway, just thought I'd mention it.
 
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