Like Tree0Likes

Old Merc. 350 mag heating up.

Reply
Old 07-26-2008, 09:52 AM
  #1
VIP Member
VIP Member
Thread Starter
 
PARADOX's Avatar
 
Join Date: Dec 2005
Location: Florida
My Boats: Formula 272 Sold, 26 Infinity, 4 sale, 08-33' Avanti 4SALE
Posts: 2,697
Default Old Merc. 350 mag heating up.

350 Chevy block. Lower unit is off, impeller like new. What would cause motor to run hot? didn't overheat,, just running hot so I quit using it.
Thermostat? Any good and easy way to check water flow?
BTW it's running hot on higher RPM's

Thx
p
PARADOX is offline  
Reply With Quote
Old 07-26-2008, 09:55 AM
  #2
Registered
 
Join Date: Jul 2007
Location: Austin,Texas
Posts: 2,111
Default

Track water flow thru upper housing, water hose thru transom , power steering cooler. Also check risers for obstructions.
MOBILEMERCMAN is offline  
Reply With Quote
Old 07-26-2008, 11:20 AM
  #3
Registered
 
Scott B's Avatar
 
Join Date: Dec 2000
Location: Slightly North of Cuba
My Boats: Donzi Criterion SS, X-18 , 16 OB, Z-235, F-14, Magnum Missile
Posts: 2,914
Default

Bad risers will do that.. Also, just because the impeller looks good doesn't mean the rest of the pump is. Check the base and upper housing carefully. Next step is to check the entire water system. Backflush everything, see if pieces of old impeller or whatever are stuck in it. Last, pull risers, inspect for blockage..
Scott B is offline  
Reply With Quote
Old 07-26-2008, 11:26 AM
  #4
VIP Member
VIP Member
Thread Starter
 
PARADOX's Avatar
 
Join Date: Dec 2005
Location: Florida
My Boats: Formula 272 Sold, 26 Infinity, 4 sale, 08-33' Avanti 4SALE
Posts: 2,697
Default

Impeller is replaced. Pump looks good. Checking stuff on motor and hoses next. But not today. Time for lunch with the Avanti.
PARADOX is offline  
Reply With Quote
Old 07-26-2008, 01:36 PM
  #5
Registered
 
Join Date: Aug 2004
Location: naples,florida
My Boats: 19'baron to name a few
Posts: 3,542
Default

Check the hose that comes off the transom plate inside of the transom.I know it is hard to get at and inspect but I had one that was restricting flow at higher RPMs.

Paradox where in Florida do you live?
tommymonza is offline  
Reply With Quote
Old 07-26-2008, 01:46 PM
  #6
Registered
 
Join Date: Jul 2007
Location: San Diego
My Boats: Advantage 28ft Sport Cat w/ pair of 8's
Posts: 989
Default

Quote:
Originally Posted by tommymonza View Post
Check the hose that comes off the transom plate inside of the transom.I know it is hard to get at and inspect but I had one that was restricting flow at higher RPMs.

Paradox where in Florida do you live?

I was thinking the same thing. There have been a number of guys that have had the hose kink/ collapse due to age.

BTW, if you back flust it and it flows well it could still be bad and collapse under suction.

Darrell.

Last edited by DMOORE; 07-26-2008 at 01:47 PM. Reason: ADD
DMOORE is offline  
Reply With Quote
Old 07-26-2008, 08:55 PM
  #7
Registered
 
Scott B's Avatar
 
Join Date: Dec 2000
Location: Slightly North of Cuba
My Boats: Donzi Criterion SS, X-18 , 16 OB, Z-235, F-14, Magnum Missile
Posts: 2,914
Default

On an alpha, it's not under suction, it's after the pump...
Scott B is offline  
Reply With Quote
Old 07-27-2008, 09:47 AM
  #8
VIP Member
VIP Member
Thread Starter
 
PARADOX's Avatar
 
Join Date: Dec 2005
Location: Florida
My Boats: Formula 272 Sold, 26 Infinity, 4 sale, 08-33' Avanti 4SALE
Posts: 2,697
Default

Quote:
Originally Posted by tommymonza View Post
Check the hose that comes off the transom plate inside of the transom.I know it is hard to get at and inspect but I had one that was restricting flow at higher RPMs.

Paradox where in Florida do you live?
New Port Richey... just North of Tampa.
PARADOX is offline  
Reply With Quote
Old 07-29-2008, 12:44 AM
  #9
Registered User
 
Join Date: Feb 2008
Location: West edge of the Pacific
My Boats: Beat up ole Sleekcraft
Posts: 610
You say the pump "looks good" so I assume your getting water out the exhaust so the raw water pump is flowing. Overheating at higher rpms could mean a few things.
1. Passages blocked by pieces of impeller or chunks of rust.
2. Bad Thermostat
3. Disintegrated or disconnected impeller in the recirculation pump.
Also get a cheap mechanical temp guage and screw it in place of the electrical one. Just a thought... IS your temp guage working right?
29Firefox is offline  
Reply With Quote
Old 07-29-2008, 08:29 AM
  #10
VIP Member
VIP Member
Thread Starter
 
PARADOX's Avatar
 
Join Date: Dec 2005
Location: Florida
My Boats: Formula 272 Sold, 26 Infinity, 4 sale, 08-33' Avanti 4SALE
Posts: 2,697
Default

THanks 29.. My mistake.. I should have said the "impeller lokos good" not just the "pump"

Impeller is removed and changed. THe old impeller did not had any peaces missing and was still fexible, not dry.
Will check thermostat and all the water ways. guage is good.
Possible circulating pump on the block.
More research is due.
Thx
PARADOX is offline  
Reply With Quote
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
BRIAN73
General Q & A
17
07-16-2011 07:12 AM
PARADOX
General Q & A
7
08-27-2007 02:59 PM
Miguel
General Q & A
0
08-16-2004 04:05 PM
justinVIP
General Q & A
17
11-18-2003 11:43 AM
Cattitude
General Q & A
1
08-11-2003 06:53 PM



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 On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 11:57 PM.


Copyright 2011 OffShoreOnly. All rights reserved.