Go Back  The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > The Boating Forum
Reload this Page >

cooling system problems with mercury 200 hp efi

Notices
The Boating Forum

cooling system problems with mercury 200 hp efi

Old 09-05-2010, 11:21 AM
  #1  
Junior Member
Thread Starter
 
Join Date: Sep 2010
Location: arkansas
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Default cooling system problems with mercury 200 hp efi

I'm new here and a new owner of a 99 mercury 2 stroke 200 hp efi. The motor has a cooling issue I am trying to sort out. I would appreciate any help I can get. The motor runs great. However, at idle it has water pressure around 12-15 lbs and pegs the gauge at anything above about 2000 rpm. The pee hole has a strong steady stream. The motor runs strong with no alarm until I try to run around 5000 rpm (about 60 mph) then I get the dreaded steady beep of the overheat alarm. The alarm then shuts off as soon as I get out of it. According to the former owner, this only occurs at higher water temps (upper 80s here right now). I suspect either a restriction of water flow or a bad alarm. I would genuinely appreciate any advice on how to trouble shoot this scarey problem to a solution. Thanks for any help.
Old 09-05-2010, 12:14 PM
  #2  
Junior Member
 
Join Date: Aug 2010
Location: Savannah, GA
Posts: 24
Likes: 0
Received 0 Likes on 0 Posts
Default

My best guess would be the Water pump.
Old 09-05-2010, 12:53 PM
  #3  
Senior Member
 
Join Date: May 2009
Location: SW FL
Posts: 1,685
Received 965 Likes on 524 Posts
Default

water pressure is too high... something's clogged or stuck

change the t-stats and check the poppet valve
Old 09-05-2010, 12:55 PM
  #4  
Senior Member
 
Join Date: May 2009
Location: SW FL
Posts: 1,685
Received 965 Likes on 524 Posts
Default

Originally Posted by Chief Ron View Post
My best guess would be the Water pump.

he's getting 12-15psi at idle and pegs the gauge at higher speed...why would you guess pump?
Old 09-05-2010, 01:00 PM
  #5  
Senior Member
 
Join Date: Apr 2009
Location: Pearlington, MS
Posts: 186
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by roozter View Post
water pressure is too high... something's clogged or stuck

change the t-stats and check the poppet valve
I agree with the above but I have also found that sometimes the impeller will "spin" on its hub at higher speeds as well. But with your pressure gauge showing good or pegged water pressure at 5k rpms its a restriction somewhere and T-stats and poppet are great places to start and hopefully END.
Old 09-05-2010, 02:00 PM
  #6  
Senior Member
 
Join Date: Jan 2009
Location: Iowa
Posts: 9,624
Likes: 0
Received 6 Likes on 5 Posts
Default

Originally Posted by roozter View Post
water pressure is too high... something's clogged or stuck

change the t-stats and check the poppet valve
Agreed and if a saltwater boat make sure there is no salt buildup in the passages if so get it out of there.
Old 09-05-2010, 05:42 PM
  #7  
Senior Member
 
Join Date: Sep 2003
Location: Tampa FL
Posts: 4,010
Likes: 0
Received 3 Likes on 3 Posts
Default

I would first look at the poppit and t stats - they don't produce much pressure so something is up - I would also check the pressure gauge line just to make its clear and reading correctly
Old 09-05-2010, 07:50 PM
  #8  
Senior Member
 
Join Date: Mar 2009
Posts: 112
Likes: 0
Received 14 Likes on 8 Posts
Default

A stuck / blocked poppet will cause high pressure on idle, and overheating once over 1500rpm. The thermostats control the temperature up to around 1500rpm or 8lb of water pressure when the poppet is meant to be opening.
I put a tap on the hose leading to the poppet from the top of the block as I was trying to increase temps in the cold water, all it did was increase water pressure on idle. The more I blocked it off the higher the pressure gauge went while idling.
Old 09-05-2010, 09:49 PM
  #9  
Junior Member
 
Join Date: Aug 2010
Location: Savannah, GA
Posts: 24
Likes: 0
Received 0 Likes on 0 Posts
Default

My father had an Optimax 130 doing the samething. We pulled the pump and the enitre thing was full of corrosion. We slapped a new one on and she was good to go.
Old 10-01-2016, 04:20 PM
  #10  
Junior Member
 
Join Date: Oct 2016
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Default Cooling problem

The problem sounds like the 2 thermostats located on the top of each head. They get corroded every couple of years. They are cheap and very easy to replace yourself.
Old 10-01-2016, 07:57 PM
  #11  
Admirals Club Admiral's Club Member
 
Blue agave's Avatar
 
Join Date: Aug 2016
Location: West Central FL
Posts: 523
Likes: 0
Received 159 Likes on 78 Posts
Default

Poppet
Old 10-02-2016, 08:26 AM
  #12  
Senior Member
 
Join Date: Mar 2011
Location: Algonac michigan
Posts: 5,940
Received 1,013 Likes on 542 Posts
Default

Originally Posted by Blue agave View Post
Poppet
Since this thread is almost 7 years old,it's probably been fixed by now...newbies.
Old 10-02-2016, 10:13 AM
  #13  
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Nov 2005
Location: Central Jersey
Posts: 7,961
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by muskamoot View Post
Since this thread is almost 7 years old,it's probably been fixed by now...newbies.
Boat sold years ago. Thanks.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.