Engine wont pump water!

Marcdohc

Hello all, 

My boat, 05 FV 300 with Merc 5.0's

My problem, Last year for the last couple times out I noticed the starboard engine was reading cold. I figured it was the gauge, it seamed to run just fine. I posted this issue last fall and you folks said install a new thermastat, so I did. When I went to winterize the engine I notice that there was barely a spit of anti frieze coming out of the exhaust. Well, I just hooked a hose to the outdrive to crank her up and noticed there was nothing coming from the exhaust. So I took the thermastat out and dropped it in a pan of hot almost boiling water to see if it would open and it did. So I installed again, but this time I took apart the other one on the port engine so I could make sure I did it right. But still no waterflow. I than opened a winterizing plug at the bottom of the engine and ran the engine and after it sputtered a bit from the hole it then poored with a steady flow. I thought I must of found the airlock and fixed it. After I installed the plug again I ran the engine again and still no waterflow. I then pulled the upper winterizing plug on the raw water pump and ran again and got no water flow. I then pulled the plug at the top of the thermastat housing and ran and no water spouted. Any ideas what it could be? By the way the raw water pump was installed new last year. 

Thanks for reading, Marcdohc

Black_Diamond

I'd double check the impeller, I think it was Tiki that ran across bad impellers (new parts too). It was too short and would not draw water.

DanD2

Was it a new raw water pump or just a new impeller installed??? Either way, to me, it sounds like the impeller is not working properly. I replaced both of mine last year with a Blue run dry from Globe and they both failed within weeks of each other. They cracked where the shaft goes through and would not spin in the housing. Unless you've got the cool fuel module, it's pretty easy to remove the pump on a 5.0

Marcdohc

Uugh, kinda what I thought. Thanks,

blueman9155

I've gotten in the habit of having the impellers replaced at 3 years. Boating around sand bars in Lake Michigan can wear them out so just wanting to avoid issues