Mercuiser 180 temperature issue

[Benny67]

Looking for some feedback here.

I'm having issues with my portside motor increasing in temperature upon load. I noticed it was running warmer than last year and was 20 degrees higher than my starboard motor. When I got out of the harbor and throttled up the temp jumped from 160 to 180 in 2 min. The starboard motor was below 160 (as usual) with the same load. In the past both motors ran at the same exact temperature and I've never seen this issue before.

I changed the thermostat and it didn't make a difference. It idled at around 160 and as soon as I throttled up, it did the same thing.

Prior to launching, I changed the entire water pump, did a compression test and a leakdown test all of which were fine.

Last night, I capped off the heat exchanger and filled it with CLR and let it sit overnight. This morning I drained the CLR and ran a gun cleaner through some of the heat exchanger holes and started it up. The temperature never reached over 140 at idle for 20 min. I'm hoping that it solved the problem but I'm unsure because I couldn't take it out due to the need to be somewhere else today.

My question is, anyone ever see an issue like this and if so, what was the solution?

I'm not losing any antifreeze, there's no smoke in the exhaust and if I continue to run the engine I'm sure it will overheat. That is if the CLR trick I did doesn't work. I have good waterflow to the exchanger as well.

My thought is it has to be the exchanger. Anyone can confirm from past experience of one failing?

 

[Scott Danforth]

Start with the raw water impeller.

Do you have the updated heat exchangers?

Cleaning the heat exchangers is a yearly maintenance item like pulling the drives and checking alignment

 

[Benny67]

Start with the raw water impeller.

Do you have the updated heat exchangers?

Cleaning the heat exchangers is a yearly maintenance item like pulling the drives and checking alignment

Raw water pump is new. Not just the impeller, the entire housing.
Heat exchangers are 4"
I'm kinda stumped at this one but like I wrote, I didn't run it after the CLR and the rod cleaning. I only idled the motor at the dock for a half hour or so and it didnt raise over 140 F (better than before I did it) I'm kinda looking for someone who actually diagnosed a bad exchanger and see if their problem had any similarities to what I'm seeing

 

[jhamblett]

Take both covers off the heat exchanger to make sure each individual tube is clear.

 

[Benny67]

Take both covers off the heat exchanger to make sure each individual tube is clear.

I did. Since I did, I haven't taken it out for a test with a load on it. Like I wrote earlier. My point of this post is I was hoping to find someone who has had a similar situation to compare it to.