With the hose muffs on, my boat doesn’t draw water. With muffs on and me pressing the muffs really tight, I get intermittent surging of water through the system. However when I let go, it stops pulling water. I figure this might be an air leak but where should I start? It’s gotta be between the muffs and the water pump. A clamp not on tight enough, a crack in a hose… it’s not leaking water at all. Can anyone post a YouTube video on how to go about this? I do have a new impeller on hand but want to see if this is an air leak first.

I would first check the obvious, the impeller ! If it looks good, then chase what is harder to find

does it draw water appropriately when the boat is in the water?

If the impellor is in good shape, check for blockages. First, I'd pull the hose off the back of the impeller housing and make sure water is getting through the transom and to the impellor housing. Then I'd pull the hose off the oil cooler and look for old pieces of impellor clogging it up. Then keep moving forward from there.

Your troubleshooting, holding muffs for better seal and getting movement of water is a sign the impeller is shot. Change the impeller and it will suck water and pump it.

Looking through the hose holes…. The impeller looks fine.

I assume your drive isn't a dual water pick up. Perhaps there's blockage between engine and sea water pump typically at a cooler. You may want to back flush.

I wouldn’t have a clue honestly, I’m only a boat mechanic when something breaks and I have to learn how to do it lol. It’s a 1990 454 mag with a bravo 1…

looking in the hose ports will only tell you that the fins are there. the issue is that when they sit the fins stay folded over and will not seal well enough to pull water. also you dont know how good the housing is as it does not take much wear to make them slow to pump. if it is more than a couple years old or sat for a year or two with out use change the impeller and housing before wasting time on the rest.

It hasn’t been used a lot of I think it’s been used enough to keep it all good. The sea pump housing is 6 years old, so it’s not really that old. The impeller looks to be okay. My question is with the surging, it did pull water but only in surges when I made a very tight connection with the outdrive and muffs, essentially forcing the hose water into the system. I think the surging aligns with it pulling in air before the pump. Or maybe the impeller wasn’t able to pull it but it was surging for some reason.