Water Flow Force 125

[Justinde]

Hi All

I am yet to add a tell-tale, however, I did the waterpump etc, and solved the overheating issues (touch wood), but when I was on the water with a mate checking the water flow form the leg, at idle, it pumps water hand over fist ( really great flow), yet at WOT, the water just dribbles out.

Is this usual? Should I not have more water at WOT than at Idle?

Silly question, probably a simple answer, but now over to you guys.

Cheers

 

[notop]

Re: Water Flow Force 125

Sorry, duplicate reply.

 

[notop]

Re: Water Flow Force 125

I am assuming that when you say you checked the water from the leg, you meant the water coming out of the two little holes at the back of the intermediate housing. At idle, water and exhaust comes through there because there is not enough pressure for it to force itself to the bottom of the leg. But at higher revs, there is lots of exhaust force to push the water and exhaust all the way out the (bigger) exhaust hole in the bottom of the leg. So the water level in the leg never gets up to the two little holes in the intermediate housing at high revs so you will at most only see a vapor of water coming out of those two holes.

 

[Frank Acampora]

Re: Water Flow Force 125



They all vary a bit. However, the real test is whether or not the engine is overheating.

Basically, the two holes in the back are called the idle relief vents. When the engine is sitting low in the water--like at idle-- backpressure is high and these two vents allow exhaust to escape. Without them, backpressure would force exhaust back into the cylinders and idle would be crappy. The engine would also probably stall.

Now, again, when the engine is sitting low in the water, the inside of the leg fills with water and it will exit with the exhaust out the idle relief vents--usually as a spray. Cooling water always exits into the inner leg to cool it and the exhaust down tube. There is a gasket around the bottom of the exhaust downtube and usually several holes in the inner leg flange with plastic plugs or not. If the gasket is worn or missing, or if the correct amount of plastic plugs are not there, water will drain into the lower unit faster than designed.

THUS: At higher speeds, you may or may not see water exiting from the vents--it all may be exiting from the exhaust snout.

If you look closely you will see the water exiting from the small white 55 on the 10 foot tunnel hull. You can also see it spraying from the black 90.

 

[Justinde]

Re: Water Flow Force 125

Hi All ( And Frank)

She overheats SOMETIMES but without the tiny tach attached, I don't know if I am over revving the engine, so, using NO tacho, and running at what SOUNDS like WOT, never overheats. When I push it further ( no advance in boat speed) she overheats.

She does 42 MPH all day and happy. When I push her to say, 43 MPH, she overheats. Without a tacho, it could be the difference between 5500 and 5800 rpm. Its 20 years old, and I am happy with 42 MPH. I'll attach the Tiny Tach and report.

Cheers

 

[Frank Acampora]

Re: Water Flow Force 125

Over-revving the engine has relatively litle bearing on overheating. If the engine overheats, replace the impeller (again, if you have already done it) or check the water passages and thermostst.

There is one exception: I boat in a section of river designated as a cooling pond for a power generating plant. During peak loads in the summer, the water is at least 100 degrees at the outlet. When I pass through that slug of water, the engine overheats.

And BTW: At about 3/4 throttle, the engine is at maximum timing advance. When you advance the throttle further, the engine makes a lot more noise, uses a lot more gas, and the boat only goes 2-3 MPH faster. However, more gas burned equals more heat produced.

 

[Justinde]

Re: Water Flow Force 125

I REALLY want to check the thermostat, but cannot, for the life of me, crack the bolt ( which is a bolt with a flat blade screwdriver slot). Its REALLY REALLY REALLY REALLY REALLY stuck.

I should do the thermostat, as the waterpump, water passages etc are all spot on, so really, its the last link in the chain.

Tiny tach this weekend, and pics to follow next week.

 

[Frank Acampora]

Re: Water Flow Force 125

two of those bolts enter the water chamber and if they have not been removed and coated with anti-seize, they will corrode -- almost to the point of welded.

To get them out, you go to sears or other toll supplier and buy a hand held impact screwdriver. Use the bug blade and twist in a counterclocwise direction while smacking the top with a hammer. Be forewarned: You may snap one off.

Replace them with allen head capscrews -- 1/4 X 20 OR 1/4 X 20 with 3/8 hex heads. You can find the 3/8 headed bolts on Evinrudes and the flange bolts of Force engines.

Test the thermostat in a pot of water while it is heating. It should start to open before the water boils and should be open fully in boiling water.