2020 250SS overheat and not peeing on muffs

[Matt Ostrem]

2020 250SS with 550 hours and a new water pump at 500 hours. The motor has suddenly stopped taking in water when I flush it on the muffs. I use the double sided rectangular muffs. During a recent flush I noticed it wasn't peeing so I kept an eye on the temp and it shot right up. I killed it when it was approaching 200 within a couple minutes of starting the flush. No water is coming out of the prop either. Put the boat in the water and it starts peeing almost immediately and runs about 140-150 all day. Muffs have a ton of water coming out of them on both sides and it all just seems to flow out between the muffs and lower unit.

Any ideas?

[Moonlighter]

Yes.

the best muffs to use are the ones with small round soft cups. And - importantly- put them on from the prop end.

Turn the water on hard and wait 30 seconds, then start.

[Matt Ostrem]

I'll give that a try. I've had the motor for two years using the same muffs and this is a sudden change.

[Moonlighter]

Go carefully.

Suggestions:
- connect the hose to the flushing port turn hose on but don’t start the engine. Is strong water stream water coming out the telltale? May indicate whether there is a blockage
- re water pumps, as noted in another recent post, lack of use is worse than lots of use for impellers. They can get a set in the vanes and don’t pump well. So even though it may have been changed 50 engine hours ago, if it has sat unused for many months then that can be the issue. If you do a water pump service make sure you do the full kit, not just the impeller.
- water pressure and volume from the hose is important. Make sure the hose is turned on strongly and youre getting good flow to the muffs.
- old muffs the cups can harden and not do a good job any more.

I had been using the double sided rectangular muffs on my DF115. Then got a DF50 as well, and it would overheat using them, so I changed to the small round ones with soft cups and put them on from the prop end, they worked perfectly in the 50 and the difference on the 115 was immediately noticeable in how much faster the telltale started up.