Bob...is your exhaust plate dry-stacked?........Lots of water pressure?
Brack,
No, not dry stacked, and I wouldnt go so far as to say lots of water pressure, but normal. I am getting 0 psi at idle, and as the speeds come up, the press comes up too. Probably around 8 psi at 55-60 mph and around 10-12 psi at 70-75, and I am not sure faster than that because I am not brave enough to look.
That being said, my engine was set up with 3 pissers. There is no crossover on top of the heads, they both empty out the back of the cowl, along with the pressure relief hose. The gauge is also an aftermarket Nordskog reading off the stock merc sensor, which reads 175 or so after a hard run, so I dont know if that reads right at all. I am putting the crossover back on the top of the heads as part of my cowl change. I would think that would up my pressure 1-2 psi.
In the winter, just as general maintenance, I replaced the pump impeller, cup, base plate and all gaskets in the H20 pump assembly, and I pulled the water dump hoses off the engine because I am getting ready to put my new CF cowl on. I had to pull the powerhead to get the old cowl pan off and I checked the area where the water comes into the block just to make sure it was clean, and it was. Since I was messing around I pulled the tstat housings to see what size hole was in the washer and it mic'd out at .122" so around 1/8th. But I have heard of folks running 3/16ths and 1/4 in them and was wondering if I should do the same.
Was the water pump impeller a little tired? Maybe. I ran it for all last season, and I am not sure how many hours it had on it from when Bill ran it previously, but I would say probably not much. So I dont figure to pick up any press from the change. Last season I was also running on a 7" JP at 1/8" above the pad, and this season I will be on a 10" JP set up at even.
Since the first day I had the boat, the temp read 175 after a hard run, even in the spring with cooler temps, and it ran the same in the summer, with warm temps, so I figured I didnt have any cooling issues.
Now, my 280 is running 260 elecs (I dont know if that should make any difference), and if that means that I should be running in the 135 deg range, then I guess I need to get some larger holes in the washers. But I always figured that 175 deg head temp was probably around 135-145 water temp.
I apologize to everyone for coming off argumentative. My plan is to run it as is, and see what the new jackplate / prop shaft height do for pressure & cooling and go from there.
So I guess my question should be, what head temp should I see after a hard run? Its an easy enough change to get some more washers and drill them for 3/16 and 1/4 and see what I get for temps. I just need to know what the value should be.
