Notices
Like Tree5Likes

Mercury Optimax Overheat Riddle

Old 10-08-2018, 08:35 AM
  #1  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default Mercury Optimax Overheat Riddle

2008 115 Mercury Optimax

About 30 days ago I hit a sandbar and sucked up a bunch of compacted sand and shell that clogged my cooling system. I eventually got some telltale stream going but not good flow and started getting overheat alarms*. I limped back to the ramp. Changed water pump and gasket(oem parts always), was due for it anyways. Better flow but still not right and still getting overheat buzzer. Replaced the strainer in the motor. Pretty good flow after that. Idled for 20+ minutes with no alarms...thought I was good, but as soon as put in on plane I get the alarm within 10 seconds or so. The telltale looks good and the water doesn't feel hotter than usual even when the alarm is going off, but I presume it must be.

There is a check valve in the water flush hose between the hose hook up and powerhead. The shell had this clogged to where it would only piss on the earmuffs. I eventually got the check valve to open up but today I noticed that when the engine is running in the water there is a small amount of water leaking out of the hose attachment. If that check valve was working properly it seems there shouldn't be ANY amount of water coming that way. It seems it would be a very small reduction in water pressure/flow but maybe that's all it takes. Any chance that check valve is the issue? I don't know what else to try?

*I don't have smartcraft or water pressure gauge, just audible alarm. The alarm I getting is the solid beep, and the motor reduces RPM to "guardian" speed.

Thank you for input advice in advance!
feather thrower is offline  
Old 10-08-2018, 08:36 AM
  #2  
THT Sponsor Admiral's Club Member
THT sponsor
 
Join Date: Jan 2008
Location: Fire Island NY
Posts: 1,121
Default

Check your poppit valve - that controls water flow over 1500 rpm's
Lone Ranger likes this.
rdiesel01 is offline  
Old 10-08-2018, 09:18 AM
  #3  
Senior MemberCaptains Club Member
 
Join Date: Aug 2002
Location: Baltimore,Maryland
Posts: 5,464
Default

Been there with an Opti..I had bits of Shell clogging the Strainer for the Air Compressor....Bits holding the Poppit Valve open..Mine overheated at idle...I pulle the Thermostats,New Poppit Valve,Cleaned the Air Compressor Strainer,New water Pump and Housing on mine.
Lone Ranger is offline  
Old 10-08-2018, 12:50 PM
  #4  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

Update. Opened up the thermostat and poppit. Both had lots of sand/shell..the poppit area was completely clogged up. After cleaning and reinstalling both I took it for a water test. Still getting alarm and the telltale is actually WORSE at idle now, and the poppit and thermostat filled back up with sand and shell completely. Got it home, cleaned both again. Checked strainer-that was clear. It will piss running on earmuffs but now won't piss when hooked up to the flush adapter(which it would Friday), so I must still have blockage. I'm going to just take my tools with me to the ramp next time. Run, clean poppit & thermostat, run...until it stops getting debris in it. I think I'm making progress?? Lot's of pros on here...any advice?
feather thrower is offline  
Old 10-08-2018, 01:32 PM
  #5  
Admirals Club Admiral's Club Member
 
Join Date: Jan 2013
Posts: 4,587
Default

Backflush it....
avalonandl is offline  
Old 10-09-2018, 05:51 AM
  #6  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

By that you mean hook the hose up to where the tell tale is and flush ?
feather thrower is offline  
Old 10-09-2018, 05:55 AM
  #7  
Admirals Club Admiral's Club Member
 
Join Date: Feb 2016
Location: NSB, FL
Posts: 410
Default

remove the strainer, thermostat and poppit valve and hook up to hose (not on muffs) and use the pressure of the hose to flush all the debris out
swaddict is offline  
Old 10-09-2018, 06:14 AM
  #8  
Senior Member
 
Join Date: Apr 2018
Posts: 320
Default

Remove the strainer poppit and /T stat,DROP THE LOWER UNIT so all the shells don't go down into the water pump and flust it every which way with pressure until the sand and shells are not in your engine.Even remove the zincs and blow pressure through them into the cylinder head.
Lone Ranger and Dacman like this.
sailingman is offline  
Old 10-09-2018, 01:20 PM
  #9  
Admirals Club Admiral's Club Member
 
Join Date: Sep 2017
Location: Jacksonville Beach, FL
Posts: 33
Default

I have 2001 225s. Be careful removing strainer for compressor cooling. First one I removed sheared in the block. Fun getting it out. Don't know about 2008 models but mine is plastic.
Bushwacker366 is offline  
Old 10-09-2018, 04:44 PM
  #10  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

yup...they are still plastic and look like they belong in a residential irrigation system instead of an outboard motor. I tried to be careful, but mine still sheared off. I had the same fun as you getting it out.

I got a little more shell out back flushing with the poppet out but still clogged. Really trying to avoid dropping the foot again. I'm just going to keep running up to speed, clean poppet and stat, rinse and repeat...
feather thrower is offline  
Old 10-12-2018, 07:58 AM
  #11  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

Ran the boat for about 45 mins yesterday. Poppet is finally running clean and I didn't get any alarms at higher rpms. I did get a singe beep at idle while tied up. Indicates running cold and the telltale wasn't warm at all, so I think it was. After running on plane for about 15 minutes I came back to idle and temp climbed until overheat alarm went off. That's the only time it did. I would NOT get the same alarm just idling around or running around. Big improvement but still not quite right. Going to change the thermostat b/c it's gone bad twice before. Maybe a poppet kit too just to cover everything. Installation seems very straightforward, but anything to watch out for? I will give props to Mercury for making the thermstat and poppet very accessible on this motor. Same with spark plugs and everything else that requires servicing.
feather thrower is offline  
Old 10-19-2018, 05:44 PM
  #12  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

Same story after putting in a new thermostat. It overheats but only under very specific circumstances which are: running at higher rpms on plane and then going to neutral and staying there. I can feel the temp of the telltale climb and he alarm goes off after about 4 minutes or so. If I go from higher rpms and drop back to idle speed, but in gear, it stays cool and no alarm. Can run at all other rpm ranges w/o overheating.

As it should with a new water pump(gaskets and faceplate too)the telltale appears good and strong when in idle speed forward and all other reps other than neutral. Itlooks less strong when in neutral. The rpms appear the same the same as idle just in gear, so I don't understand the psi difference?

I was hoping to avoid dropping the LU again, but at this point I'm just going to do what sailing man said I should. I get the feeling he might know what he's talking about...
King P.V. likes this.
feather thrower is offline  
Old 12-28-2018, 10:27 AM
  #13  
Member
Thread Starter
 
Join Date: Aug 2007
Location:
Posts: 80
Default

I didn't want to ghost this thread, but wanted to run it a few times before I updated. I got 3 trips where everything ran properly and no alarms, probably 1.50 hours run time at various RPMs. Thought I was golden, but no...last trip got 3 alarms around 1000-1400 rpms. No alarms when running on plane and was able to leave it in idle N at the dock running for 10+ minutes with no alarms. I don't even KNOW for sure that these are overheat alarms but I 98% sure based on what's been going on. Question: the poppet valve replacement looked different than the original, but still fit the same. Any chance this is the issue? I can provide pics of poppets if that's a realistic possibility
feather thrower is offline  
Old 12-28-2018, 01:47 PM
  #14  
Senior Member
 
Join Date: Mar 2006
Location: Long Island, NY
Posts: 6,497
Default

Different poppit probably just updated version.

You must have really clogged that motor good. There is something still moving around in there causing intermittent issues. One day will happen at the wrong time. Powerheads are expensive and you had many fair warnings. I would buy a pair of head gaskets, pull the heads and clean it all out of the water jacket and be done. Change the temp sensor also. All cheap insurance compared to what can happen.
magua likes this.
Local Motion is offline  
Old 12-28-2018, 01:47 PM
  #15  
Senior MemberCaptains Club Member
 
Join Date: Mar 2003
Location: United States
Posts: 9,185
Default

Thermostats control temp at lower rpm and poppet controls at higher speed once the pressure increases.

Also make sure temp/low water pressure is still the issue via smartcraft gauge or scanning codes. Could be a new issue that you are contributing to the old issue.
captbone is offline  
Old 12-28-2018, 02:52 PM
  #16  
Admirals Club Admiral's Club Member
 
Join Date: Nov 2018
Posts: 238
Default

Did you change the water pump OR just pull and inspect it?

The sides of the impeller need to seal to the cup and plate in order to generate the pressure needed to blow off the popet valve. The tips of the blades move the water (volume). If there is not enough pressure to blow the popet off it’s seat, it would cause a mid range overheat.

Hopefully you get her resolved.

If you do pull the lower again, you can pull the tstats out and flush up from the water tube with a garden hose adapted to it. Put some fender washers in place of the tstats just for flushing. Put the tstats back after flushing.

ajtec is offline  
Old 12-28-2018, 04:24 PM
  #17  
Senior MemberCaptains Club Member
 
Join Date: Feb 2005
Posts: 1,082
Default

My 2000 135 has many over heat alarms - I have done virtually everything that has been recommended/suggested by amateurs and professionals. Yes - i had the mostly unknown cooling bypass loop installed, water pump kits/impellers, poppit valves, thermostats, sensors, compressor filter etc. and still it alarms. I can run up the river for 4-5 miles and nothing. Stop (no shut off) and on acceleration it alarms and shuts me down to 1200 rpms. Start and stop all the way home and get alarm on every acceleration. On occasion I can throttle up after a alarm shut down and If I do it quick it will let me run. Back to the shop this winter for one more shot (and $$$). May be that certain Optis are cursed.
lodel is offline  
Old 12-28-2018, 05:47 PM
  #18  
Senior Member
 
Join Date: Jan 2011
Location: Northern Burbs of the Motor City
Posts: 6,305
Default

Originally Posted by lodel View Post
My 2000 135 has many over heat alarms - I have done virtually everything that has been recommended/suggested by amateurs and professionals. Yes - i had the mostly unknown cooling bypass loop installed, water pump kits/impellers, poppit valves, thermostats, sensors, compressor filter etc. and still it alarms. I can run up the river for 4-5 miles and nothing. Stop (no shut off) and on acceleration it alarms and shuts me down to 1200 rpms. Start and stop all the way home and get alarm on every acceleration. On occasion I can throttle up after a alarm shut down and If I do it quick it will let me run. Back to the shop this winter for one more shot (and $$$). May be that certain Optis are cursed.
Yes!

Had a 01' Opti 135 in warranty that threw an over heat alarm within the first year. That was the beginning. After dealer "charged me $500 + for spark plugs and decarbonization/ lower unit top off and a few other non - over heating "must haves" I did some research into this issue.

The engine never overheated underway - ran as cool as 105 in cold spring Michigan conditions and around 120 underway in the heat of the summer. Overheat for me was always during long periods of idling below 1000 rpms. Engine would get hot nearing 180 on the Smartcraft gauges and holding no matter what at the low idle speeds. Upon powering up it would throw the alarm and I would need to bring the boat back down hit the throttle and the temp would drop instantly. This point I realized it was most just a low idle scenario in my case and through research found that many Opti's experienced the same thing.

Mercury released the "bypass" kit cost about $80 installed it myself and it didn't make a difference at all.

Long story short the low idle overheat is very common - however just engaging the button on the shifter to a neutral while idling and gently revving the engine would get the temps quickly to 145 from 180 within seconds. The low speed overheat is pretty typical and imo a result of the inherent design by the "smarter" guys with degrees.

edit:

someone mentioned head gaskets might be a good idea after so many alarms in the case of the OP.

I just want to add I am a gauge freak cars/trucks/planes/trains gotta know where all base lines are under all conditions. The 180 degree temps I would experience would occur for hours at troll since that is the primary reason for going with the Opti at the time with the Smartcraft gauges and supported troll mode. I did lots of extended trolling just under 1000 rpms in the heat of the summer chasing Muskies and would watch the gauge cycle from 165 through 180 - 182 at the highest. Always felt as though that was to high but after season after season of the same conditions I put over 1500 hours on that engine and sold it a few years back running just fine - never a hiccup cept the "minor/normal" overheat issue.

Last edited by magua; 12-28-2018 at 05:54 PM.
magua is online now  
Old 12-29-2018, 04:27 AM
  #19  
Admirals Club Admiral's Club Member
THT sponsor
 
Join Date: Apr 2013
Location: Baton Rouge, LA
Posts: 5,079
Default

Is there a strainer on the air compressor water inlet line? Similar to the newer 3.0L Optis. You really need to find out what the alarm actually is.

If you plugged it up bad enough, powerhead removal may be required to gain access to the water passages in the adapter plate. We’ve had to do this on some commercial applications after fighting overheat issues.

Is that engine using the small diameter impeller? If so it’s a high pressure, low volume pump and that contributes to a lot of issues with overheating Optis once they have a few cooling restrictions. If the entire water pump kit (housing, gaskets, impeller, etc.) wasn’t changed, I’d start there. Those small vane impellers take a set very easily as well as the housings become scarred easily with sand and grit.
davidwademarine is offline  
Old 12-29-2018, 08:08 AM
  #20  
Senior Member
 
Join Date: Jan 2011
Location: Northern Burbs of the Motor City
Posts: 6,305
Default

Originally Posted by davidwademarine View Post
Is there a strainer on the air compressor water inlet line? Similar to the newer 3.0L Optis. You really need to find out what the alarm actually is.

If you plugged it up bad enough, powerhead removal may be required to gain access to the water passages in the adapter plate. We’ve had to do this on some commercial applications after fighting overheat issues.

Is that engine using the small diameter impeller? If so it’s a high pressure, low volume pump and that contributes to a lot of issues with overheating Optis once they have a few cooling restrictions. If the entire water pump kit (housing, gaskets, impeller, etc.) wasn’t changed, I’d start there. Those small vane impellers take a set very easily as well as the housings become scarred easily with sand and grit.
True dhat. Mercury increased size of impeller and housing on later releases of Optis since they were aware of the higher running temps logged.
magua is online now  

Thread Tools
Search this Thread