1988 150 xr4 merc with low, then high, then low water from "pee" hole....????

Hey guys, I'm new to this site and hope I can get some help here.... My 150 is barely peeing water out of the telltale, then it flows like it's got a brand new impeller, which it does, then back to poor flow and keeps doing that. I've replaced impellers before and I've double checked everything, can't figure it out. Couild my pump housing be cracked????

It could be a bad housing (or seal) or water tube issue.

I would start troubleshooting this way -

1- check the tell-tall (pee) hose for blockages - bugs/critters/mud can be partially blocking it
2 - (temporarily) remove the thermostat and fire it up - if the flow is good, replace the thermostat
3 - if neither of the above cure the problem replace the poppet valve (called a pressure relief valve back when your motor was new) - the spring may be shot and it's due if it's 3 or more years old anyhow
4 - if all else fails, get a water pump "kit" - save the impeller for the next change but use all the gaskets/seal and new plate
5 - check the water tube - they do occasionally corrode (especially in salt water) and can blow a hole through the side - you may also have to the check the seal where the watertube connects to the exhaust plate at the base of the powerhead (a fair bit of work that requires removing the lower unit and the exhaust housing (leg) so you always hope one of the earlier steps solves the problem.

Ok, I removed both thermostats and it's working great now!! I put both thermostats in a pot of hot water and watched to see which one didn't open but they both opened at the same time... I ran the engine with one thermostat in at a time and got good water flow. Maybe one was bad for awhile without me knowing and the other finally went bad? I'll get a thermometer tomorrow and see what temperature the thermostats open at, should be 145*.
My question is: are the thermostats fully closed at engine start-up and if so, how does the tell-tale get it's water flow before the engine warms up enough to open the thermostats, I don't get that...???
I'd really like to see a water flow diagram of where the water goes thru the engine after going up the water tube to the bottom of the power head.....
Thanks for all your help and I'll post my results tomorrow for my temperature test.

Chris

I tested both thermostats today, one opened at 160*, the other at 175* so it looks like I'll be getting some new thermos.....
Anybody out there have a good water flow diagram for this motor, I'm still curious how it goes thru the powerhead....