We are a group of Verado owners from all over the world that encourage the free exchange of information about the Verado engine. We are not affiliated with Mercury Marine and accept no advertising. We strictly exist from members contributions.
If you would like to join our group all we ask is that you register. If you want to join the contributor board, see the message down below in the free discussion area which explains the benefits of that section.
Your source for Verado Information
February 21, 2020, 09:43:52 am *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: CLICK HERE to become a contributor and gain access to the Expert section. PROBLEMS? email me at glenersly@mac.com-DO NOT CONTACT PAYPAL
 
   Home   Help Search Calendar Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Engine Temp Cycling  (Read 3479 times)
3boys
'CHOEY' 2005 BOSTON WHALER 305CQ
Veteran
*****
Offline Offline

Location: Sag Harbor, NY
Posts: 222



« on: May 29, 2016, 03:21:47 pm »

Hi guys,

Hope everyone is enjoying the Memorial Day weekend - and taking a moment to pause and remember those who fought to keep us free.  Our Boy Scout troop replaced all of the American flags at the veterans' graves of our local cemetery today - always leaves a lasting impression on the boys.

My port 2005 250 seems to have a water temp issue.  While running at cruise, etc., the temperature cycles from 145F to 165F and then back down.  The 20 degree increase takes ~10 seconds while the drop back to 145F is much faster.  I replaced the t-stat and have the same results.  Engine has good water pressure - comparable to the stb engine.  I tried to 'reverse flush' the engine but no luck.

Any thoughts on what might be causing the temp cycling would be greatly appreciated!

Cheers,
Chris

Logged
VeePeeKoo
Member
**
Offline Offline

Location: Finland
Posts: 10


« Reply #1 on: May 30, 2016, 05:36:01 am »

I have exact same problem 2009 300 Verado. Changed t-stat and water impeller, not helped. Please inform here if you can find the cure.
Logged
thunderstruck
Moderator
*************
*****
Offline Offline

Location: Louisiana
Posts: 544



« Reply #2 on: May 31, 2016, 08:03:40 am »

 Long story but to the point.  I replaced my tstat and poppet valve a while back but broke one of the bolts on my poppet valve.  Wanted to use the boat so I installed the poppet with only one bolt and started having the same problem you are describing. 

I believe my problem was that my poppet valves installed with only 1 bolt was sticking shut and then opening because the valve body was crooked in the housing with only 1 bolt.  When I got my poppet installed properly the problem went away.

I am not saying you have a broken poppet bolt but if your poppet is worn it could be sticking in the housing.

Otherwise I have seen folks on here replace the water temp sensor.

 
Logged
3boys
'CHOEY' 2005 BOSTON WHALER 305CQ
Veteran
*****
Offline Offline

Location: Sag Harbor, NY
Posts: 222



« Reply #3 on: May 31, 2016, 10:17:37 am »

@thunderstruck,

Thanks for this feedback.  I suspect my issue may also be related to a sticking poppet valve and I've just ordered two replacements.  Your comment about breaking off one of the bolts is indeed my fear of trying to change out the valve.  I have 2005 engines and very likely the poppets have never been changed.  Any advice as to how I might reduce the risk of snapping bolts when trying to remove it?  Should I try heating them with liquid wrench?  Also, is it possible to undertake this repair while the boat is in the water or would I be asking for trouble?

Thanks again,
Chris
Logged
thunderstruck
Moderator
*************
*****
Offline Offline

Location: Louisiana
Posts: 544



« Reply #4 on: May 31, 2016, 10:20:46 am »

Heat the exhaust tube and apply some penetrating lubricant.

Mine snapped off with minimal torque using a 1/4 " ratchet so be careful.  I have some comments on here if you search.
Logged
SaskAngler
Member
**
Offline Offline

Posts: 17


« Reply #5 on: June 24, 2016, 10:40:29 am »

I'm seeing the same temperature cycling on my 2015 200 6 cyl.  What was the starboard engine running at, temperature wise?  I'd also be curious to know whether changing the poppet stopped the cycling?
Logged
3boys
'CHOEY' 2005 BOSTON WHALER 305CQ
Veteran
*****
Offline Offline

Location: Sag Harbor, NY
Posts: 222



« Reply #6 on: November 27, 2019, 09:27:58 am »


Good morning,
Now a few years later, with 1250 hours on my 2005 250's, the temperature cycling on my port engine continues.  It rises up to ~158F then drops down to 140F and climb back up to ~158F.  Engine has new LU (so new poppet valve) and T-stat.  Any ideas what could be causing the cycling?  I'm fairly certain its not the T-stat as I've replaced 3X with same result. 
Thanks everyone and wishing each of you a most enjoyable Thanksgiving with your families!
Chris
Logged
thunderstruck
Moderator
*************
*****
Offline Offline

Location: Louisiana
Posts: 544



« Reply #7 on: November 27, 2019, 11:16:12 am »

This issue is widely reported.  I believe the cause is that there is no or very little water bleed past the Tstat when the tstat is shut.  This causes the water in the block to heat up (no flow) once the Tstat finally senses the hot temp it opens and floods the Tstat outlet (where the temp sensor is) with hot water and the temp sensor shows high temps.

With the Tstat open the water cools and the Tstat shuts again and the cycle repeats itself. 

This is reported more from areas where boats are run in cold water.  The problem is not as pronounced in the south with warmer water.  The colder the water the more likely the Tstat is to completely shut.

The fix I believe from Merc is to drill a very small hole in the Tstat to allow a small amount of water to flow so the Tstat thermostatic tube sees the water temp in the block better.  1/8" or less.  If you drill the hole too big the Tstat will not function properly.

Search on here and thehulltruth.com for more info.
Logged
Theredman
Member
*
Offline Offline

Posts: 2


« Reply #8 on: February 02, 2020, 01:08:34 pm »

Iím having similar issues on my 2016 300. But itís from 145 to 175. Approximately. Recently purchased last fall, and only ran when water temps were 75 to 80. Now here on the central coast water temps are 55 to 60 and the cycling  happens when Iím on plane. Can I run it like this or do I need to fix?
Logged
paulswagelock
Contributor
Member
***
Offline Offline

Posts: 96


« Reply #9 on: February 02, 2020, 04:41:58 pm »

If no alarms, run it as is.
Logged
Javenius
Member
*
Offline Offline

Posts: 1


« Reply #10 on: February 07, 2020, 02:41:31 pm »

I have had the same issue on my 2016 250 Verados. Purchased new in 2017.

I boat on Lake St Clair in Michigan.  Spoke to dealer when new and he said "let's see what happens when the water warms up". Sure enough, when the lake warmed up, the flucuating water temp stopped.

It has acted the same for 3 seasons now. Never an alarm.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.4 | SMF © 2006-2007, Simple Machines LLC Valid XHTML 1.0! Valid CSS!

Disclaimer: Views expressed in Veradoclub.Com's open forum are from private individuals and do not in any way reflect the views of Veradoclub.Com, or the Veradoclub.Com staff. Activities and modifications described or displayed in this publication and it's pages may be potentially dangerous. Veradoclub.Com does not endorse or make any claims to their safety or performance.