Overheating mercruiser 3.0

This is a viewer requested video and thought it would be a good one to shoot quick. In this video I show you all the components to a mercruiser 3.0 cooling system and why it may overheat and what to do to try and figure it out.

0:00 Intro
0:50 Video explanation
2:46 Cooling system and why it may not work
8:27 See you in the next video

List of all related cooling parts and links to purchase (note some parts may vary based on year and version of outdrive etc.)

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[vassilyknigge]

Thanks for all of the amazing information. Now if only I could find a video of someone explaining this as good with a 3.7l mercruiser.

[martincameron]

What if you accidentally forget to take the ear muffs off and you run the boat in the water for 10 minutes. I know that it would reduce water flow to the recirculation pump of water but wouldn’t it still get some water? There is a connection on them for the hose. What should you check after that?

[joesoprano]

I have a Mercrusier 3.0 and one thing you didn't mention is the Exhaust Manifold. If that is plugged from years of use and a build up of rust, it will overheat the boat. I had to replace everything from
the risers to the exhaust bellows. Hope this helps a few of you.

[coryhunborg]

Dude this video was so ridiculously helpful, thank you!

[jackjohnson]

Did you guys ever get it figured out? I had a 3.0 that kept overheating, went thru and replaced everything, pump, impeller, hoses, t-stat, still overheated. It wasn't until I tore the engine down that I found that upon removing the t-stat housing/ hose manifold from the head that a piece of old impeller had found its way up to the head and got lodged right there, it had rust and barnacles or rust bubbles all over it and had clogged that passage completely, come to find out on that block, that is the bypass passage and if it doesn't have flow, the coolant system just doesn't work at all. The actual explanation is more technical but that's the jist of it.

[flowers]

what great video, I learn alot, I did first step replace impeller in outdrive still overheat now will check thermostat let you know what happen thanks,
you are a profesional . teaching showing is a profession .

[antonioarias]

Gracias por sus videos, saludos de sinaloa mexico

[iselili]

What a great, informative and to the point video, thank you!!

[stevecarabetta]

Thanks for the video, big help. I'm still overheating. Wracking my brain trying to figure it out. I noticed in your video u don't have water coming out of the prop. Maybe my mercruiser 3.0 is a different engine design. I have 2 exhaust ports on the upper part of the outdrive, one expelling water and the other exhaust. I also have about 1/3 of water volume coming out of center prop. I've replaced impeller, thermostat, poppet valve assembly, thermostat and poppet valve housing. I guess I'll change the pump even though it looks and sounds decent. I found a lot of crud caked in the thermostat housing and fear the exhaust manifold may be choked with it. Any ideas or input u may have would be great-Steve

[mybugguypestsolutionshoels]

Hi Dale. Hope all is well. I took my belt off of the recirc pump/alternator and there was no resistance on the recirc pump it just freely spins. The impeller is new and the thermostat is new. Per this video you were saying that if the recirc pump sins geeky that could be the problem?

[mikesumo]

Quick question does a Mercruiser Bravo 1 outdrive have the impeller in it like the 3.0?

[chudbuckingham]

My boat was overheating so I took the thermostat out and started it without the top on and no water was circulating. It was bone dry. I just had the impeller replaced. Could it be the impeller again? I’m sort of at a loss

[TechLoop-HQ]

Great video dale! I’m currently trouble shooting my 4.3 mercruiser alpha one

Would you happen to know if most of this is still applicable?

[christianconner]

I feel like I need to check my impeller after watching. That could be one of the causes. The previous owner left it docked and a thousand baby oysters attached themselves all over in the nooks and crannies of the out drive. I enjoyed hours of picking them out of the crannies with a sharpened flat bladed screwdriver and a cold beer in my hand. However I noticed them inside of the water intake ports and I guess I just thought they would somehow get flushed out.

I haven’t attempted taking that stern drive apart yet. I will search on YouTube to see if anyone attempted that.

[bradfelger]

What type of oil is put in your hydraulics?😮

[davidsimmons]

Port side exhaust has a light spray while the starboard is working fine

[travisbrown]

Is there a link to the parts? Great video!

[johnmarkreed]

Your intro sounds like my life brother

[richmac]

I'm having an issue with my 3.0 Merc. A couple years ago I started noticing that my temp gauge was reading higher than normal (went from 165 to over 200). No noticeable changes in engine operation like pinging or run on after shutting it off, just a higher temp indication. Changed the impeller (even though the original was in perfect condition) and changed the thermostat (though testing showed the original was working perfectly). Pulled the wire from the sending unit and gauge stopped reading so I know that it is doing something. Water seems to be flowing well through the engine and out. Used an infrared non contact thermometer to measure temps along all the water lines coming and going from the thermostat housing - nothing above 165. Water pump on the engine looks good, no leaks. I'm not certain I trust the temp gauge (most of the gauges on the gauge cluster jump around quite a bit) or maybe sending unit? Suggestions as to what to look at next?

[djrockv]

I have a 4.3 Volvo penta that’s overheating.put muffs on and no water running back out should i check my impeller in my strem drive first.