Mercruiser overheating on muffs

[bheston]

Got the water pump">raw water pump pulled last night but quickly discovered the previous owner left me with a broken bolt in the block

After 4 hours, left handed drill bits, easy-outs, cursing, praying, crying, anger, an finally acceptance, I finally got it out. That cost me about 2 years off my life expectancy!

[Fiftybucks]

most here have struggled with the broken bolt issue. it is good you found instead of just taking the back of the raw water pump off. that bolt is required to provide tension to the belt and support for the fuel pump action against its cam.


photos of those hoses?

[bheston]

Okay - I'm in "broken bolt" company.

I didn't get to take photos (yet) of the hoses but I will. I did get photos of the impeller and pump. The impeller was perfect - no damage at all. The pump is not what I expected. I bought the standard Mercruiser kit with housing and it not anywhere close. The boat is a 2010. Is this a newer pump or older pump design?

[Fiftybucks]

newer Gen7 Mercruiser partner Hardin Marine
supposedly better... almost any other design would be welcomed.

those part are available also. i'd replace and keep for emergency spare.


i did notice 2 different size hoses on the water pump... that fitting with the ball valve may very well be an engine inlet.

[bheston]

I think you might be right. Here is a terrible picture but one that shows a mystery black hose (I suspect from the through hull) joining a "Y" fitting with the red hose. The combination then connects to the back of the raw water pump.

[jimbunyard]

Well I think now we know why your pump wouldn't pickup from the garden hose. When you get it all put back together, put some kind of lubricant on the impeller, close the valve on the front pickup, hook up your muffs as before, and try again. Hard for the r/w pump to pull any suction when the front valve is open...

I'm betting that the previous owner had some run-ins with a few mud banks and clogged up the foot pickup so that his engine overheated, so when he installed the freshwater system he provided two pickups.

Can't say I like the idea, seems more like double the chance for screwups, rather that insurance against clogged intakes.

Would be good to know what outdrive you have, which would give us a better idea as to what advice to offer.

From the picture you supplied, the Mercruiser part number for the impeller you need is likely 47-59362T6, the Sierra (an aftermarket supplier) p/n is 18-3224, and the 'run-dry' impeller by Globe Rubber is 2001. Some people have pump wear problems with the globe impellers; I've used them without problems but they're expensive.

Your impeller looks fine to me, if there isn't any rubber rubbed off on the housing, it's probably good.

[Dennis.G]

Not in exact response to your issue as it seems your water intake is actually via a thru hull. That said, the clamp-on water muffs are a real hit or miss device. I could not get them to work properly on my small boat with Mercruiser outdrive. I got these instead and they do work well: https://www.wholesalemarine.com/flus...waAqlzEALw_wcB

[Fiftybucks]

DennisG.... those were the ones I have also. they work and don't slide off. I think if he closes that ball valve and tries again it will work as per Jimbunyard

[a64pilot]

I wouldn’t try it again before contacting a dealer.
However you should be able to discern if the foot and thru hull are interconnected by placing the muffs on and opening the water, if they are connected water will free flow out of the thru hull.
But it should also be running out of the exhaust, and it wasn’t

[bheston]

I bought a set of the factory Mercury muffs with the stainless steel rod as suggested. With the RW pump removed and the hoses laying in the bilge, I will install the muffs on the Bravo III outdrive and turn on the water (engine will not be running for these tests). I want to verify water flows out of the hose inside. Then, I will use a fake-a-lake and do the same for the through-hull intake. Again, to verify the water flows. There are one of two theories to be proven:

1) The boat has dual intake pick-ups: foot pick-up and the through-hull pick up.
or
2) The boat has a through-hull pick up only and the foot is blocked-off.

[bheston]

To close this topic and for others who may encounter the same issue, the problem is solved. I put the fake-a-lake on the through hull intake and duct taped the outdrive intake. Turned the water on and no water flowing out the RW hose disconnected in the bilge. Hmmm. I then swapped the water line to the outdrive with the Mercury made muffs and closed the ball valve on the through hull. Turned the water on but still no water out the RW hose inside the hull. I grabbed the shop vacuum and put vacuum on the hose as I ran the water. Once I gave it vacuum, the water was flowing in the hose. Keep in mind the engine is not running and the RW pump is not yet installed. I checked the through hull and sure enough, it flows too when I use the shop vac. I guess a standard garden hose may not have enough volume and pressure to push the water up especially if there is leakage at the muffs or fake-a-lake.

As suggested, I closed the through hull connection and the engine ran nice and cool with the Mercury muffs. Lesson learned, close the through hull port before running on muffs if you have dual pickup like me. Thanks for all who replied.