F300 Overheats at high power settings but not at low to mid. What thinks you?

[oldmako69]

Running in at the end of a long day I get an overheat buzzer and message to shut down No 2. Shortly before the alarm went off I noticed reduced water flow through the pee tube. But, I've seen this before and didn't freak out. But I was ready for that alarm.

I tilted up the engine and the intakes were clean. Boo. I let it cool down and fired it back up. Water was present at the tube. I throttled it up and watched the water flow decrease and stop. Shut it down.

I determined that the water would flow up to about 3000 RPM but above that, it would stop. So I limped home with one at 4200 and the other at 2600.

Take a look at this pic. The missing gasket piece in particular. My hunch is that at high RPM too much water was shooting out of the broken section of the gasket and not going up the cooling tube. I remanned these water pumps late last fall. They have 80-100 hours or so. The impellers look and feel new. At 160 per kit I am leaning toward just buying that gasket and running it.

Think this might be the culprit for my overheat and loss of flow?


OK....the pic won't go through. Arrrgh. It's the THIN gasket that runs around the bottom perimeter of the water pump housing on a 2014 F300. The gasket seals the housing to the metal plate that the impeller spins on. So, there's some high-pressure water there. About an inch and a half are missing. Maybe two inches.

[TownsendsFJR1300]

Part # 24? Or #17?



Capture.JPG

[oldmako69]

17. This seal keeps the high-pressure water generated by the impeller from going anywhere but UP to the engine. It seems to me that a two-inch piece missing will allow just enough water to shoot out from under the water pump housing to prevent the engine from cooling at high RPM.

No idea why the site won't allow me to load an iPhone pic.

[99yam40]

17 looks like an O ring to me not a gasket

very strange it ran well for about a year and now has a problem.
where did that chunk of O ring go and how did it get out of that slot/grove it was sitting in?
you may need to replace the housing also if it will not hold the O ring in place

[oldmako69]

OK. O ring. Sorry. Def number 17.

As far as your questions, I have no idea. I have done this type of water pump rebuild probably 12-15 times. I used to do it annually on my 225s because the kit was only 45 bucks. Amazingly, on the F300s they're 160 bucks. Essentially the exact same parts. An impeller, a few O rings, a gasket, a new impeller plate, and bolts.

I've always thought that the ring was too small in diameter and that the slot was too puny to securely seat the ring but it has always worked.

I'm just going to replace that O ring and button it back up. I'll know the first time I wind her up (P-tube) if that was the culprit.

On a side note, these engines have not given me a single nick of trouble in the last year. They start immediately, idle like butter, and will push the boat with ease across the powerband. At lower cruise speeds I am constantly looking at 1.8-1.9 MPG. And that's pushing an 8000-pound boat at 30 plus knots while burning 18-19 GPH. I cannot find fault with that.

[Keithbaja]

I would always use "GASGACINCH" on that "O" ring seal. Also the one on top of the cup and around the cup itself. Try it, Your like it...
.

[TownsendsFJR1300]

Any warping of the housing itself usually causes cooling issues.

Your o-ring seal partially missing would definitly cause issues...


Re the pic, I "snip" a pic from the parts section here and save to my photos. Then upload.
Being it's just a simple black and white pic, not an actual picture you physically took of your engine, much less "data" and it'll post..

.
.

[oldmako69]

I'll certainly check the surface of the housing to ensure it's flat before I reinstall the pump.

That ring sits in a very shallow slot so the idea of adding gasket compound seems valid. I added a thin layer of marine grease in there to hold the ring the last time I remanned the pump. Hopefully, I can find the ring locally this morning. If not, I'll order one. It's forecast to blow here the next few days so I'm not going anywhere anyway.

Super pleased actually that I found this ring busted. Otherwise, I would have been scratching my head trying to figure out what to yank next. Hopefully this is the issue. It makes sense to me that a bit of missing O ring could easily allow enough water to escape to prevent adequate cooling at high RPM.

Thanks for the opinions.

[Keithbaja]

Oldmako, its just not any gasket compound. I've been using it for 40+ years. Marine gaskests don't need any sealers. But for that seal it helps to hold in place. Also seals the w/p cup so it dosnt suck in air. Had a 23 mako in Costa rico. Damn tough boats. But I've moved up to cats and will never look back !!

[oldmako69]

Necropost....

It's still overheating. Both Telltale streams appear the same, namely weaker than I'd like, but no weaker than all of last season with no overheating. The W-Pump housing is flat. The pump impeller and gaskets all refreshed. It's fine till I get it up to speed, say anything over 3300 RPM. The stream disappears and the alarm sounds.

I have downloaded and printed pages 104-106 of the F300 manual. These are the diagrams of the cooling water path and the associated bits. I guess my next step is to start removing hoses and T-Stats and looking for an obstruction to the cooling path. Cylinder heads last.

Questions for the masses...

1) Is there a typical culprit or area or obstruction? The T-Stats were clean the last time I looked at them and offered no obvious clues. As were the anodes. Yes, salt was present in the orifices but no more than I have seen over the years on any saltwater-cooled engine. I recall watching a YT vid years ago where a guy was holding up a plate that he had removed from a YAM OB and the passages inside were jammed with sand. I assume that sand was injected when running the boat in shallow water and bumping the bottom with the skeg.

2) What is the name of the chemical that you can add to a trashcan to rid the cooling passages of salt and crud? I'd like to try this technique before I start taking stuff apart. In the winter months, I don't have fresh water available to flush and I am wondering if I just have salted-up cooling jackets around the cylinders. It's not SALT AWAY, though I will ADD that to the mix. It's something else. Does anyone know? Is it RYDLYME? I found that on Amazon for 31 bucks a gallon. They recommend 1:1 ratio, so I'd have to buy a ton of it to fill a trash can halfway. I wonder if another, cheaper Limeaway product would perform the same?

[99yam40]

seems to me if higher speed or maybe just higher RPM causes loss of tell tale and overheating,
then maybe the causes could be exhaust gases or air to be sucked into the water pump or pushed into the cooling system up in the head/block area displacing the cooling water

Is it possible something is causing disturbed water/air bubbles to the lower unit pick up at higher speeds

maybe dampener seals in lower unit by water pump leaking exhaust gasses into the area of water pump?
leaky head gasket, or corrosion hole in head/block, exhaust plate, etc?


how about citric acid to remove minerals
should be able to find powder and mix to the strength you want.
use hot water to help dissolve the powder and it also speeds up the desolving of minerals


On another note, I have helped remove loose build up from motors by dropping the lower unit and hooking up a hose to the water pipe running water thru the motor and injecting compressed air into the water hose also from time to time to help move sediment up and out the stat openings with the covers removed.
but never tried that on a big motor.

you can also use a tub of Rydlime mix with a pump in the tub ,(lower unit off) hose to water pipe. just need to catch what comes out of the motor into the tub and keep it recirculating.
no need to fill a large container to run the motor with lower units on.

[oldmako69]

I like the idea of citric acid. I'll need a lot of whatever I use, so cheaper is better. Even if I have to go to Costco and buy 10 gallons of Vinegar.

Both pick-ups are clear, upper (2) and lower (2) so I think I can rule that out.

Engines have about 900 hours. Boat new to me in the fall of 2019. No idea how they were treated before that or how often they were flushed if at all. They appear nearly new and in excellent condition. They run like chainsaws. As previously mentioned I don't have fresh water during winter to rinse my engines, but I seldom run the boat in winter anymore. A Buddy of mine has a set of very high time (>1800 hours) YAM 250's on his Southport and he never flushes them, so I have to wonder just how much help flushing does. As it is, I am using a weak well pump to flush. Not much water PSI IOW, so I am just hopeful that the freshwater helps dissolve the salt crystals.

<<"maybe dampener seals in lower unit by water pump leaking exhaust gasses into the area of water pump?
leaky head gasket, or corrosion hole in head/block, exhaust plate, etc?">>

I have no idea. When I took the lowers off to replace the water pumps I looked up each with my scope and noted nothing out of the ordinary. But, I may not have gone up high enough where the pathway bends. No idea how I would diagnose a leaky head gasket (compression test?) or corrosion hole in the block or exhaust plate. There is nothing going on externally that I can see.

So if I pull hoses, T-Stats, anodes and find nothing too sinister (no smoking gun) I guess the next step is to pop off the heads and peer into (and scrape out) the cooling passages???

I'll try running the boat at lower RPM and shoot the heads with an infrared temp gun. It may be that one side just leaps out and is running much hotter than the other and will help me troubleshoot the issue. Idunno.

I'll try and come up with a plan to simply circulate the solution through the engine using an electric pump of some sort and hooking the hose directly up to the water pipe in the leg. Running the engine in a trash can will likely cause the water to quickly get too hot to adequately cool the engine and some sloshing is liable to occur as well. I wonder if my freshwater wash-down pump is up to the task? Or would I need something beefier? I could simply disconnect its fittings and hook the batts up to a charger.

Thanks for your input.

[oldmako69]

61S5K9kjclS._AC_SL1500_.jpg

This would probably make a lot more sense. I could get away with using a lot less water and a lot less chemical, whichever I decide. Maybe even a simple drywall bucket, or a smaller 10-20 gallon tote. Plug this in and walk away. Let it run all day. 60 bucks.

https://www.amazon.com/MEDAS-Portabl...xpY2s9dHJ1ZQ==

[oldmako69]

My buddy with the SouthPort has a pump like the one I posted.

Will back it down the ramp and let it run to operating Temp. Maybe bump it to 1800 or so. Shoot the engine with the temp gun all over. Then remove the LU and attach a large bucket of sumpin-sumpin to the water intake tube. Fire up the pump and recirculate that solution for a few hours. Cross fingers.

Hook LU back up and repeat step one. Take temp readings. If different, great. If no joy, grab wrenches and dig in.

[99yam40]

My buddy with the SouthPort has a pump like the one I posted.

Will back it down the ramp and let it run to operating Temp. Maybe bump it to 1800 or so. Shoot the engine with the temp gun all over. Then remove the LU and attach a large bucket of sumpin-sumpin to the water intake tube. Fire up the pump and recirculate that solution for a few hours. Cross fingers.

Hook LU back up and repeat step one. Take temp readings. If different, great. If no joy, grab wrenches and dig in.

sounds like a plan.

when I mentioned air bubbles at speed, I was talking about something on the hull may cause disturbed water flow putting air bubbles at the water pick up.
do you have any bottom machine heads or thru hull fittings in front of the lower units that could cause this to happen?

edit
I just reread the whole thread, and noticed it is only one motor that overheats, and that you have not replaced the plate, cup, and housing when you did that impellor.
might try a kit just to rule those out