1/8th Washers in the top of the head

[propmanjay]

64 to 1 scares me with Klontz. What RPM do you turn it? I have always run 32 to 1 with 333.

 

[rmills280]

64 to 1 scares me with Klontz. What RPM do you turn it? I have always run 32 to 1 with 333.

it scared me at first when glen reynolds suggested that i run 64-1 with 333b but i was going through oil like crazy so i cut back. i can turn the 280 7800 but i run it the same in my 260 that will turn 8500 plus

 

[rmills280]

Wow.......that is good news........do you run it pretty hard now and then? Your oil mixture seems pretty far off the recommended 32/1 or 40/1 but obviously, you have been very successful doing it.

i dont know what running easy is, i try once in a while but cant take it for long.

 

[Volatile]

180 is WAY high for a 280 guys. Sorry but I'm sure Merc will agree. Thats WAY high for a normal race motor. Good luck, I think we've given you good advice and direction.

 

[suicidealli]

i ran over a huge leaf a few years ago, and it blocked off my water. i hit 200* water temp. the motor had 20 hours on it. i got it home, and i scuffed 2 cylinders just a little bit when i pulled the heads.

roy

 

[Alli-drenaline Rush]

I didnt think the 280s run poppets or thermostats, at least mine doesnt have them in it. My motor doesnt run hot at all at idle, probably around 100-110 deg when idling. I have checked everything, and nothing is amiss, clean as a whistle. I think it has something to do with running a stock merc sensor on an aftermarket gage.

I have a new waterpump in it and we will see when I put it back in what happens.

From page 4B-3 of the Merc 2.5 EFI service manual applicable to motors with serial numbers 0G857020 and above, poppet valve is not installed on this engine (emphasis on the word "not" is in the manual).


Bob to answer your original question, basic chemical engineering....... Q = m * cp * delta T

q is constant (heat rate into the water), cp = constant (heat capacity of water)

So if the restrictor is bored out from 1/8" to 3/16", that will increase m (water flow through the head), and thus delta T must drop to compensate (though not necessarily by a lot).

The manual says that water exits the block in three locations

- excess water exits with the exhaust through the drive shaft housing
- water exits through a restrictor washer (one on each head) and out of the tell tales.
- water exits through a straight fitting (water dump) in the poppet valve cover (Poppet valve is not installed on this engine).

Might one or more of these exits be non-functional???

Richard

 

[Bobalouie]

Hey Richard,

The way my engine is set up, I have 3 tale tells, one coming from each head, and one thru the poppet valve cover. When I run on the hose, Water comes out of all 3, and I have water coming out of the exhaust housing, so all of the water exits appear to be functional.

The water exiting out the exhaust housing has the most volume, followed by the poppet cover tell tale. The two tell tells from the top of the head are much weaker than the poppet cover, but on the hose, I have 0 psi water pressure. With the new cowl, I have reconnected the jumper hose from the top of the starboard head to the top of the port head, so I expect that tell tale to flow more strongly in the future.

 

[FLYING BUTCHER]

I just saw the post and wanted to ad my two cwnts (one of those been there done that deals??) I have run every size hole in the washers from 1/16th to 1/2"!!!! NOT A SINGLE DIFFERENCE IN WATER PRESSURE OR TEMP EVER. Did same thing as Bob trying to pick engine techs brains about this issue and never found a single person who could come up with a reason for against sizes. I've had several 280s on just about every type of set up and they all ran 175 during the summer bar none. Sorry about the water pump Bob, the lower unit was completely rebuilt including water pump (less than 10 hours before you got her). For me if there was a better mousetrap (back when I had her) she would have had it on her. I know you are just wrenchin and hope you are enjoying doing it but no need to spend a bunch of money just to be doing it, save it for gas looks like we are going to need it??? have fun be safe

 

[Bobalouie]

Hey Bill,

Nothing to be sorry about for the waterpump. Just normal preventive maintenence / jacking around.

 

[Volatile]

Alli-drenaline Rush >> larger holes allow MORE water to drain BEFORE going thru the heads. They WILL run hotter with larger holes. Water enters around the cylinders and moves up the block, then enters the heads at the top and flows down them and dumps out the area under the poppet hole (triangluar shaped exit) and thru the poppet opening. If your water pressure gauge is mounted to either the top of the head or to the top of the block, water pressure will not change enough to notice. Water will be bleeding off before the heads however and it is measurable with a temp gauge on the heads themselves. Anyway, 180 is very warm for any race motor or even a fishing motor for that matter.

 

[Alli-drenaline Rush]

Volatile,

You are right. If you bore out the restrictor washers, block temperature should fall somewhat due to an increase in water flow through the block up to the point where the additional water exits the system through the bored out washers...... but..... head temperature will rise since water that would have removed heat in the heads has exited the system pre-maturely through the bored-out restrictor washers (same principle espoused in my earlier post

 

[280ALLY]

My 280 would stay around 170-175 in the summertime,but wouldn't open the stats in the winter time when water temp was in the 40's....

did it every yr, with different gauges,different sending units,
different impellers,after a rebuilt lower,etc....
everybody else who ran a 280 on the same body of water with a stock 280 ran the same way...

did this for 4 yrs,no alarms,everybody else's was the same also..

I never saw 180 & up, but when the water is near 90 degrees,it will run in the 170's, and won't break 135 when the water temp is in the 40's...