On 7/17/20 12:11 AM, wrote:
On Thu, 16 Jul 2020 17:04:13 -0700 (PDT), Mike
wrote:

On Thursday, 16 July 2020 16:20:13 UTC+10, wrote:
On Wed, 15 Jul 2020 18:10:37 -0700 (PDT),
wrote:

Hi, I have a 40hp Mercury outboard that sounds an overheating alarm when revs, get over around 4500 rpm, this outboard is a US made 4 cyl 2 stroke 1996 mod,
first of all this outboard does not have a thermostat by design, so i replaced the impeller but the impeller blades were bent only and not realy damaged in any way so i am concerned that i have not fixed the problem, the engine is in very good condition for its age so i am wondering if any one else out there has had a similar problem with this engine and if so was it resolved and how.
regards Mike.

Are you sure about the thermostat? What is the serial number?
If you haven't checked the water pressure, that is a place to start.
If it isn't around 15 PSI or more at cruise RPMs you still have a
water supply problem. Next might be corrosion in the water jacket.
There are a number of schemes to flush with salt away or just vinegar.

Hi, Thank you for your response, the S/N is OB095842, yes i'm sure about the thermostat. I have had the boat out since but due to another problem i couldn't get it over 3000 rpm so not a good test for the alarm problem, I've since had the problem fixed with a new float and needle, so when i go out in the next day or two i'll see if the alarm problem is still there.
The Mechanic said the alarm problem should be fixed now but i'm not that confident so iv'e been checking around just in case its not, so i know what to tackle next.
Regards.Mike

I am not having much look looking up that motor by S/N or finding a
60HP 4 cylinder. It must be an Australian thing.

Look up 40 hp 4 cyl 2 stroke. It's listed here
https://maxrules.com/merc_contents.php

On Sat, 18 Jul 2020 17:16:22 -0000 (UTC), Justan wrote:

On 7/17/20 12:11 AM, wrote:
On Thu, 16 Jul 2020 17:04:13 -0700 (PDT), Mike
wrote:

On Thursday, 16 July 2020 16:20:13 UTC+10, wrote:
On Wed, 15 Jul 2020 18:10:37 -0700 (PDT),
wrote:

Hi, I have a 40hp Mercury outboard that sounds an overheating alarm when revs, get over around 4500 rpm, this outboard is a US made 4 cyl 2 stroke 1996 mod,
first of all this outboard does not have a thermostat by design, so i replaced the impeller but the impeller blades were bent only and not realy damaged in any way so i am concerned that i have not fixed the problem, the engine is in very good condition for its age so i am wondering if any one else out there has had a similar problem with this engine and if so was it resolved and how.
regards Mike.

Are you sure about the thermostat? What is the serial number?
If you haven't checked the water pressure, that is a place to start.
If it isn't around 15 PSI or more at cruise RPMs you still have a
water supply problem. Next might be corrosion in the water jacket.
There are a number of schemes to flush with salt away or just vinegar.

Hi, Thank you for your response, the S/N is OB095842, yes i'm sure about the thermostat. I have had the boat out since but due to another problem i couldn't get it over 3000 rpm so not a good test for the alarm problem, I've since had the problem fixed with a new float and needle, so when i go out in the next day or two i'll see if the alarm problem is still there.
The Mechanic said the alarm problem should be fixed now but i'm not that confident so iv'e been checking around just in case its not, so i know what to tackle next.
Regards.Mike

I am not having much look looking up that motor by S/N or finding a
60HP 4 cylinder. It must be an Australian thing.

Look up 40 hp 4 cyl 2 stroke. It's listed here
https://maxrules.com/merc_contents.php

My bad I apologize to everyone. For some strange reason I was looking
for a 60 (not that strange. I am helping another guy with a 60) but it
was still my brain fart.