Ok have a question for the knowledge base that is OSO!

Im runnin a pair of 500 502's that have been sitting for a couple years (only 35-40 hours on the motors) We were having an issue with one of the motors building heat the other just seemed to have a sticky tstat.

Well we did the usual stuff, changed out the thermostats... no change. So for grins we pulled the line off that goes from the impeller to the main water pump. at an idle she has great flow, the minute you crack the throttle it sputters down to nothing..... so we thought impellers...

Spent this weekend changing the impellers and impeller bodies. One of the impellers was missing fins, the other was just folded up pretty bad. it made some difference, we can cruise at 3500 and the motor with the temp problems would run about 190. But it did hold there, the other motor ran around 170-180.

At this point it has to be a flow problem. We know that the pickups on these bravo1's get full of junk so the question is what to do? pull the motors and go through everything or is it possible to do thru hull water pickups and big sea strainers?

Im just at a loss at this point. I just bought the boat and we are trying to atleast definitively diagnose all the issues with the boat before we have to pull it for the winter.

any ideas? its a 95 formula 382, 500hp 502's, bravo 1's yadda yaddda yadddddaaa.

THANKS GUYS!

If you didn't replace the water pump housing, do that. Check that the inlet hose from the transom to the water pump isn't collapsing when you get on the throttles. Back flush engine to make sure you got all of the missing impeller out. Just my .02

I fought a similar problem a while back, turned out to be the line coming thru the gimbal, where the plastic connection bolts on inside the transom, behind the motor.. It has a wedge to keep the line place, it was collapsed and full of trash.
I'd back flush the lines-drive, check flow and look there if you dont come up with a solution

Shawn is right, you can remove part 20 in the boat (hard, but doable) and inspect the hose to see if #16 is collapsed, that is a common failure

Pull the hose in front of the oil cooler just after the water pump. You need to find the "fins" that are missing.

Pull the drain plugs on the block. I have seen if someone goes thru a lot of sand that sand will build up in the block. Back flushing will not remove the sand.

thanks for the info guys. so do you think i should be looking towards thru hulls?

As stated above, check the oil and power steering coolers.....I had the same "hot" issue with my 454 Mag and when I pulled and checked the coolers found pieces of impeller stuck in both....slows the water flow and heats the motor.....

Part of the problem with thru hulls is they can develop too much water pressure, or too little, and you have to spend time "tuning" them for the boat. They also cause drag and some loss of speed.