Results 1 to 19 of 19
  1. #1
    Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971

    250 SHO Temp Creep

    2016 250 SHO with 350hrs
    On long WOT (6,000rpm) runs the temp will start climbing. It will sit at 140-145 degrees for a while but then starts creeping up. It has not hit the threshold for an over temp alarm, but I have seen 197 degrees before backing off. Once backed off the temp will come back down to normal operating temps (under 145). Temp stays below 145 degrees under 5,000rpm. It is consistant and repeatable with enough distance (10-15miles).

    I've had the engine since new, temp was never a problem and always stayed under 148 degrees, even on 45+ min run (50+ miles).

    It starts and runs fine. Fuel usage is still same/similar as new.

    I had it to the shop, they looked at the computer (no temp alarms), and ran it but was unable get it over 140's without being on the water.
    Thermostats have been replaced by me (old ones tested fine)
    Water pump was replaced by me (old one looked fine)
    Whole Waterpump and assembly was replaced by shop
    Water pressure at WOT is over 25psi

    Has anyone experienced this?
    Looking for ideas where to begin.

  2. Member
    Join Date
    Mar 2017
    Location
    Georgetown, TX
    Posts
    767
    #2
    The avg aluminum motor in your car is 220-260deg. I’ve seen 190 on mine after a long, hard run. Let it eat!
    Lake&Bay Boca
    SHO

  3. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #3
    Thank you for confirming I'm not the only one who can get these motors above 145. My concern is it's run in Saltwater. Saltwater can experience crystallization when exposed to heat above 170 degrees, which causes deposits to form and potentially restrict cooling water passages.

    Since 2016 (350hrs) the motor held at 140-148 degrees, now it's jumped 50 degrees. I'm looking for help in understand what may have caused this jump in temperature and where to begin looking.

  4. Member
    Join Date
    Mar 2017
    Location
    Georgetown, TX
    Posts
    767
    #4
    Flush with a descaler periodically to dissolve and remove that stuff, which you should be doing yearly in the salt, regardless, in my opinion.
    Lake&Bay Boca
    SHO

  5. Member
    Join Date
    Jul 2014
    Location
    KALKASKA MICHIGAN
    Posts
    4,065
    #5
    Check your inlet screens. They need to be flush and clean against the case or it will cause high speed cavitation and do as you are describing and usually worse.
    If you just changed the oil then I am betting that is it. CJ
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.

  6. Member
    Join Date
    Jun 2004
    Location
    Ooltewah
    Posts
    521
    #6
    Quote Originally Posted by CJ1 View Post
    Check your inlet screens. They need to be flush and clean against the case or it will cause high speed cavitation and do as you are describing and usually worse.
    If you just changed the oil then I am betting that is it. CJ
    Great tip, I've also heard that the inlet screens have to sit fully seated and not have any surface outside the lower unit or cooling will suffer at high speeds. Thanks for the reminder.

  7. Member
    Join Date
    Feb 2018
    Location
    Kennesaw, Georgia
    Posts
    3,149
    #7
    On what gauge or display are you seeing your temperature?

    I suspect that you may be seeing block temperature and not water temperature.

  8. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #8
    Double checked, intakes are seated properly and flush.


    Temp is on graph coming from NEMA network, that hasnt changed since 2016.

    Waiting on parts to come in for descaling flush.

  9. Member
    Join Date
    Mar 2017
    Location
    Georgetown, TX
    Posts
    767
    #9
    Lake&Bay Boca
    SHO

  10. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #10
    Thank you Clarkbird, will post results post descale.

  11. Member
    Join Date
    Feb 2018
    Location
    Kennesaw, Georgia
    Posts
    3,149
    #11
    FYI.

    The temperature from the Yamaha Command Link network (NMEA 2000) is not water temperature. It is block temperature.

    The alarm set point for the block temperature sensor is 302 degrees F.

    I would shoot each head with an infrared temperature gun. If they are well below 180 degrees F then I might suspect the oil cooler as perhaps becoming clogged. Causing the oil temperature to be greater than it otherwise might be.




  12. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #12
    Update:
    Ran Starbrite engine descaler as per the video (pull thermostats, drop lower unit, ect.) got a bunch of mud (not surprising) but not chunks of scale or chalky bits in the bottom of the bin. Ran the descale for just under an hour and a half.

    Made a couple long runs this weekend. Temp held for 12-15min at then started creeping up (same as before). Fishing partner called it "thermal overrun" which is probably more accurate than I'd like to admit.

    Boat has Yamaha 6YC Information Station Display. I changed the layout to display water temp and the temp on the yamaha gauge goes from center (normal) to one bar up (5 bars total) at 154 degrees. Ran out of river before we could hit the high bar, but this tells me I'm seeing the temp rise on 2 different gauges.

    If it helps with troubleshooting, the temp will drop pretty quickly if I back off. i.e. it will drop from 180's down to 145 in 30 seconds or less.
    Temp will hold around 140-145 if I stay below 5300 rpm, even after/during a long WOT run, just backing off 4-500 rpm will drop the temp quickly.

    yam911, do I just let it idle for 10min then check with infrared gun or do I hire a trunk monkey to check at WOT?
    Do you think the temp would fall off this quickly if the oil was causing this? Side note: oil looks fine and oil pressure stays in normal range.

  13. Member
    Join Date
    Jun 2004
    Location
    New Orleans
    Posts
    151
    #13
    My Nizpro flashed 200 Sho was doing the same thing - temp rising to 190+ on long runs. Ended up having low oil pressure and dealer took engine apart. Cooling passages were definitely scaled up, so agree with Yam911 that it’s potentially the oil cooler. They also found some water in my oil and suspect cracked heads, so I ended up buying a new 250.

  14. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #14
    Update/resolved: Temp was still climbing after first descaler but I only had 1 gallon of Starbrite descaler, ordered 2 gallons of Bright Bay Hammerhead Descaler off amazon.

    Dropped lower unit and pumped it through for 2+hrs in a tote. I also back flushed the oil cooler lines, fuel cooler lines, some other 1/4" coolant lines. Basically anything that appeared to make sense, I pulled and back flushed.

    The tote had alot less debris/mud in it and a lot more little bits of scale, tiny particles, etc than the first descaling.

    Made a few long runs this weekend. It's 90 degrees outside and 78-80 degree water. Temp held around 144-147 and didnt push past.

    Thank you Clarkbird for the video and recommendation. Looks like a descale will be part of my annual maintenance.

  15. Member
    Join Date
    Mar 2017
    Location
    Georgetown, TX
    Posts
    767
    #15
    Glad you got it sorted!

  16. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #16
    Update: The 2 flushes I did last spring helped but temp creep was back by November.

    Pulled the oil cooler and it was pretty scaled up. I also pulled a waterjacket cover near the rectifier with similar results.

    Hard to see in the Oil cooler closeup picture but there is supposed to be a nozzle hole.

    Ran the flush on and off in the evening, soaked overnight, then ran the pump another 12hrs the next day.

    The pile of scale gives me the impression the descaler is working but I think there is only so much a flush can do. I had to scrub the oil cooler and that other cover to get them clean.

    Replaced all the anodes, thermostats, did usual maintenance. The new gaskets arrived today hoping to have them in and motor put back together this weekend.
    Attached Images Attached Images

  17. Member
    Join Date
    Jun 2021
    Location
    Jacksonville, FL
    Posts
    64
    #17
    How is it to get to the oil cooler to check it? I’ve found sandy mud in a couple places in mine and I think this may also be blocked. Also need to check the fuel cooler.

  18. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #18
    Oil Cooler is not hard to access. I'd put this at 2hrs to access and reinstall. Having an owners manual makes it much easier with torque specs, pictures, and procedures.

    It's all reusable with exception of the Oil Cooler gaskets.

    The other cover I pulled was on the STBD side below the Thermostat. One bolt is behind the fuse panel bracket, just needed to pull those bolts and slide it a little out of the way. It seemed like this area had more of a "pile" of debris on the bottom corner. Deadspot where heavy stuff can collect. I also saw metal errosion/corrosion at the bottom where all that stuff collected.

    No specialty tools needed.

  19. Member
    Join Date
    Apr 2016
    Location
    Goose Creek, SC
    Posts
    971
    #19
    Update: Not Resolved

    Ran the boat this past weekend. Water temp was 57 degrees, air temp was low 70's.

    Temp creep is still a problem. At WOT made it 5-6 minutes and hit 169 degrees. On a longer run (11-12min) later in the day (cooler), hit 181 degrees at 5700rpm.

    Obviously, the flush is helping clean out buildup inside the motor but at this time does not appear to be the primary cause of temp creep.

    Friend of a friend said he had a similar problem and replacing the waterpump housing (big white plastic part) solved it. I ordered a full pump rebuild kit, pump housing, housing gaskets, etc.