1/8th Washers in the top of the head

[K.Kiser]

I thought in stock form, the motor did not have t-stats? Is that incorrect?

Steel sleeve engines with 2 piece exhaust adapter have t-stats, and the factory nicasil/nicom engines with 1 piece exhaust adapter do not have t-stats... Engines up to the Promax are t-stat motors, and the 245's and up do not...

EDIT: According to a sale post that I just saw, that 225 Promax's or at least some had 1 piece exhaust adapters but I still think that had t-stats

 

[Volatile]

Go back to Roys post. 1) bigger holes dump water before going thru the head. Heads run hotter with bigger holes. Your temp will go up, as the sensor is in the head. 2) bigger holes WILL cool the block itself slightly more. 3) you have either a restriction (unlikely) or a bad impeller. You should see 140-150MAX and 120-125 is normal. The tiny hole does little more than let air bubbles out so there are no hot spots. We run 3/16, but the factory 1/8 are fine. 4) the heads DO run too cool, thus some guys will enlarge the holes to heat the heads more and even out temps thru the cylinder.
Bottom line, you have a restriction (in the divider or entrance holes to the cylinder are if you do have one ) or likely a bad impeller or you are sucking air. MHO

 

[Bobalouie]

Volatile,

Where are the common spots to be sucking air from? That is not something that I have checked for.

 

[suicidealli]

pull the water pump. check for melted rubber. make sure the little rubber sleeve in the water pump is still there, and not crushed. check for a great fit on the water tube. blow through the lwp. you have a restriction somewhere.. i have been there. check where the water tube goes into the one piece plate. i have seen people silcone them in, and the slicone blocks off part of the hole. 80* water temps you should idle about 110-115 tops
JMOif the powerhead is off blow some water from the hole in the plate down to maybe flush something out. i have found:\
dirt, sand, leaves, clay, mud all in hard form caked in lwp, water tube. also small sticks stuck in the little holes in the block!!!! amazing how it could travel to the block!!!


roy

 

[Bobalouie]

Thanks Roy, I will check those. I do idle at around 110-115, its only when running hard that I get temps of 175.

 

[Volatile]

How high is the propshaft height? How high are you trimming? Also check the gaskets inside the water pump. Also a blown head gasket or leaking one will cause hot running. Start at the gearcase and work your way up or vice versa. If its a blockage, the area under the divider plate on both sides where water goes into the cylinder areas (4 of them) is a common one in the block. The covers on the lower should be checked under. Pump obviously should be checked. What lower are you running?

 

[GrandLakeGAR]

Hi Bob. After break in, my 280 would always creep up to 180 or more during long full throttle runs. Slow it to idle and temp would drop right back down. I put a temp sensor on both heads and they read about the same. Tried another gauge, got the same readings. Ran it that way for 5 years and never had an over temp alarm or any DDT codes. I put that SportMaster on a 225X that uses the O-ring heads and I think the same water flow system, (except for T-stats) as the 280 and it runs cooler at WOT than at idle. Maybe it's our Okie water?? GAR

 

[GotMyAlly]

Hi Bob. After break in, my 280 would always creep up to 180 or more during long full throttle runs. Slow it to idle and temp would drop right back down. I put a temp sensor on both heads and they read about the same. Tried another gauge, got the same readings. Ran it that way for 5 years and never had an over temp alarm or any DDT codes. I put that SportMaster on a 225X that uses the O-ring heads and I think the same water flow system, (except for T-stats) as the 280 and it runs cooler at WOT than at idle. Maybe it's our Okie water?? GAR

225X t-stats are RPM sensitive. At something like 1200 RPMs, they open up and stay that way until the RPMs drop back below 1200.

 

[GrandLakeGAR]

I think you mean Poppet valve. That's what controls water flow above 1500 rpm. My point to Bob is that with the same S/M lower unit and water pump, the 225X ran cooler than the 280. Maybe 180 plus is too hot but at 7000 rpm and up mine always ran about 100 degrees warmer than the lake surface temp. After about 100 hrs on the motor with no alarms I quit worrying about the temp gauge.
.

 

[catfish123]

Last fall with my "new to me" 280, my temp gauge barely moved even after running it pretty hard...... it stayed real low............The lake temps I would guess at that point were around 50 degrees .............I wish I had a better understanding on these 280's what the real "normal" is for temperatures. I thought I had been told at the time of purchase to not expect to see much more than 135 degrees, mainly because of the lack of thermostats.

 

[GotMyAlly]

I think you mean Poppet valve. That's what controls water flow above 1500 rpm. My point to Bob is that with the same S/M lower unit and water pump, the 225X ran cooler than the 280. Maybe 180 plus is too hot but at 7000 rpm and up mine always ran about 100 degrees warmer than the lake surface temp. After about 100 hrs on the motor with no alarms I quit worrying about the temp gauge.
.

T-stats is what i was told when i called merc the first winter i had the thing if i remember correctly.....but don't quote me on that.

I do know my 225X ran cooler than any motor i've ever had. WOT in 90-100 degree days with water temps in the upper 80s, it would run 110 or so. The rest of the year, it would barely break 100 degrees @ WOT. And idled at about 135.

 

[catfish123]

My 225X performed exactly the same way as yours Neal......temperatures, pretty much identical.

 

[GrandLakeGAR]

Neal, those temps are what mine show also. Hard to compare the 280 and 225X because one is head temp and one is water temp. I added a head temp sensor to my 225X to read on the dash analog gauge and get water temp off Smart Craft. The head temp runs higher but still way less than the 280. I think the combination of more compression, more rpm and more fuel burned makes the difference. I hate to see Bob chase a problem that may or may not exist. GAR

 

[chad202]

The 280s around here that have a head temp gauge, not water temp, run about double of whatever the lake temp is.

 

[Bobalouie]

I have nothing better to do, so I can check everything out anyway. Especially since it is pretty much all apart. But, like I said before, I didnt think I had a problem. I was just curious about if you go to a bigger hole in the restricter washers, if that made head temp go up or down.

I have had the lower off the boat sitting in the spare bedroom since late November, so I checked it all out last night. It moves air, so I know there is no blockage there. All components except for the H20 housing itself were replaced as part of the winter maintainence, so all that should be good. I did find one thing when doing the replacement that may have effected water press, but I am not sure. The water dump hoses are all off, and will be replaced, and there was no blockage there. I pulled both t stat housings, and those were ok. I also checked the cavity in the adapter where the water enters the block, and it was clean. I will go back and blow some air in the t stat housings and remove the poppit cover (I know its not a poppit, but I cant remember what its called) and check in there and blow some more air thru the adapter and the block. But everything is pretty clean, so I dont expect to find anything.

Everything I have done, I just did because I have nothing better to do and I like to tinker a little bit, not because I was having an issue.

If what GLG and Chad are saying is correct, then my temps are pretty much normal at 175 or so after a hard run.

PS. GLG, I dont know if you remember me, but you invited me out to your place on Fox river and gave me my first ride in an Allison. It was about 10 years ago.

 

[GrandLakeGAR]

Sure Bob, I remember. Surprised it took so long for you to find your Allison, I knew you were serious about one. Mason's boat should be a dandy. Too bad about Merc closing the Stillwater plant and going back to Wi, Newer facility and right to work state, seemed like a dumb move to me. If you ever get over this way you can give me a ride. My son in law has a 2002 comp that I drive sometimes. Nice change from my 03. Good luck with your motor. GAR

 

[Volatile]

Sorry, but 180 is WAY high on a normal running 280. Poppet opens between 1500 and 2000 depending on the spring. Thermos open at 140 unless you have aftermarket 120 or 130's in there. Even the wildest drag motor with super high compression will not tag 180. Your 280 either had issues or your head sensor was bad or the gauge. Normal WOT on a ProMax will generally be HIGHER than a race motor because the entire poppet is removed and there is much greater cooler on a race motor. Thats why the psi is lower as well at topend. Also Nikasil dumps heat into the water faster than a steel liner. I agree with Roy, start at the pump and look for leaks or air being ingested. Work your way up. You can also buy temp sensitive crayons to see the exact actual head temp. Water temp is about 15degrees off from head temp. Meaning that a typical head temp sender does not stick down into the actual water. Also note that on ProMax or fishing EFI motors leaning out the idle will occur when the temp rises on the heads, making the motor even hotter at idle.

 

[Bobalouie]

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.

 

[rmills280]

my 280 runs 170-180-in the summer and has since i bought it new and it has been on 2 diff. boats diff. gauges with same temp readings. it has also been jump and go with 0 issues since new in 05, put rings in in 08 when it had 250 hrs on it, has 100 more on it now and all is start n go. also run klotz at 64-1 all but break in.

 

[catfish123]

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.