Overheating problem - Flushing Heat Exchanger

In this episode, we try to chase down an overheating problem on our starboard motor - a 2006 6.2 Mercruiser MX Horizon with closed cooling system.
We’ve had some overheating when running high rpm on our 341 Meridian so go step by step through the system to eliminate any coolant flow issues through the engine.
Follow along as we check the thru-hull strainers, raw water pump, transmission cooler, heat exchanger, thermostat and finally do a flush of the entire engine.

[@amirkajtezovic8310]

Wish these was more marine maintenance videos like this

[@aliassteve9055]

Two thumbs up Captain! One for the overall video. Well done! And second for the quick circles showing which bolts you wrenched on. Cool stuff, appreciate the videos.

[@AdventuresofHappyOurs]

Thanks Steve. I wanted to video the thermostat replacement but sometimes a task goes so much faster when not filming and narrating. Lol

[@jonnooney7102]

Most seemingly "good" techs will miss that because they are just too lazy or in too big of a hurry due to work load. Nobody takes care of your own interest like you ! Good job !

[@Scremndemon1]

I’ve used a cider barrel with a flush pump added with a way to back flush and different adapters to do small and large engines. Barnacle Buster is my go to.

[@boydsmith6864]

So I've not commented before, but I am so grateful for your channel and all the posts!! My 2007 Gas powered Horizon 6.2 MPI 341 is docked on Lake Lanier in Georgia. Oddly enough, 1 of 3 on the same dock! I have replaced both impellers (with your channels help). My port engine is perfect, but starboard is having a PSI issue. Reads about half the PSI of the port engine. Engine temp is right at 160 on both up to about 3200 rpm, then starboard begins to rise and at 4000 rpm and I get an alarm on starboard. I've actually switched the PSI gauges and ruled that out. I had thought maybe I have a blockage at the cool fuel assembly, but very difficult to access on starboard. I'm gonna try flushing the tranny heat exchange now and see what that does. Again, what you post is wonderful and I believe I can speak for 341 owners everywhere: THANK YOU!

[@AdventuresofHappyOurs]

Thanks! Now that you mention it, I had lower H2O pressure on the side with the overheat issue. It seemed low at idle but looked ok at higher rpm. You can flush the fuel modules by using fresh water flush adapter and removing the blue plug on the CFM and sticking a Ty rap in the hole to clear out muck that may settle in there. Water should flow out under pressure there.

[@NautiGrandpa]

I don't know what career you retired from, but you are adapting well to being a boat owner/ mechanic. 😅 I hope you have rectified the heating problem and get many more yrs of enjoyment from that beautiful boat!

[@AdventuresofHappyOurs]

Boating for about 30 years, so bound to pick up stuff along the way. Lol

[@jonnooney7102]

A short piece of threaded rod slightly smaller than the heat exchanger tubes works well to clean any calcium buildup which is usually what ends up causing the overheat in second place behind impellers and thermostats.

[@AdventuresofHappyOurs]

I didn’t get it on camera but I used a 22 caliber gun barrel brush to poke a couple of the tubes. Being I was able to see through them I didn’t bother doing much of that but it would help in severe scaling situations. Thanks!

[@Scremndemon1]

I’ve back flushed allot of engines and found some really weird stuff. Anodes , impeller parts , nuts and bolts and things you really couldn’t explain

[@tomdavis1694]

Just had to track down a nover heat issue. Went through every hose, cooler and had the HX prof cleaned. Raw water pump was rebuilt, impeller replaced and found the wear plate and cam on this pump was worn so much; at high rpm cavitation occurred and cooling water was too saturated with air bubbles to effectively cool things down. All set now.

[@AdventuresofHappyOurs]

That’s good to know! I have a new wear plate ready to go in.

[@lesliefleming4359]

The through hulls always make me nervous when away from the boat. Never know if those Bilge 😅pumps will absolutely keep up

[@MrOpaulo]

Thru hulls should always be double clamped as well

[@AchikSarih]

Merci beaucoup ❤❤❤❤❤❤❤

[@comeandtravel1]

Bro, water temps are at an all-time high in Florida this summer and you're sucking in 90 degree water - maybe warmer - so it just doesn't have the cooling capacity it once had. You might have to find a rpm that keeps thing from getting too hot.

[@AdventuresofHappyOurs]

I figured that had an impact.

[@robertbennett6697]

If sea temperature increase was the cause, both engines would be showing increased operating temps.

[@AdventuresofHappyOurs]

Something is keeping the sb motor hotter. Has been like that for years. Sea temps may just be pushing it over the threshold.

[@jimr282]

Hello Captain. What did you do for a living before retiring and managing all of these technical challenges of owning a large boat? Impressed with how you deal with all of the fun problems. Enjoy all of your videos.

[@AdventuresofHappyOurs]

I worked for Verizon as an operations manager. Was involved with many technical jobs over the years where I had to track down and solve root causes of maintenance problems. Left them after 32 years

[@Batwing2465]

Great video. Curious what you used to flush the transmission cooler tube?

[@AdventuresofHappyOurs]

Garden hose and some electrical tape to keep it from leaking.

[@Batwing2465]

@@AdventuresofHappyOurs thank you

[@Sailing.Artemis]

your tranny cooler is the same size as my diesel cooler lol

[@Ryanrock2]

Can we get the Admiral down in the engine room. in the bowels of the vessel to maybe wipe your sweaty forehead, bring you cold water?