F100 problem

[SeaArk20]

Hey guys I'm new to the forum and need a little help.
have a 2003 100HP 4 stroke. I took it out today and ran into an issue.

I put in and it ran fine for probably 10 minutes. During this 10 minutes I ran up on plane and idled around. After about 10 minutes I was up on plane and the alarm started beeping and the motor went into safe mode and cut back the RPM's. I shut the motor off. When I started it back up the alarm did not sound but the water stream coming out of the back was not very strong. The motor would idle and water would flow out of the stream but if I went above idle the alarm would sound again and the water stream would not increase. I was able to idle back to the ramp.
I’m thinking it is the impeller. How can I test to see if I should replace the whole water pump or just the impeller?

Any help or advice would be a great help.

[Sequoiha]

The only way to know for sure is to take it apart and inspect it, for the price difference go ahead and get a kit.. i would also look very close at the housing, you might be replacing that as well...

[SeaArk20]

Ok I pulled the lower unit this morning and inspected the impeller. It appears to be fine. I did check the housing and it looks like it is damaged on the inside. Could this be the problem? My thinking is that the water pump itself is mechanical so it should not come and go. Is this thinking correct in regards to the water pump? Next I will check the thermostat.
I have added pictures of the impeller and the inside of the housing.

[99yam40]

looks like you are missing the cup that fits into the housing

[SeaArk20]

The cup was there I just took it out before I took the picture.

[rodbolt17]

housing is junk.
replace the impeller with the kit and replace the housing.
also check your thermostat and pressure control valve.

[SeaArk20]

OK here is an update on the overheating problem. I rebuilt the water pump with the rebuild kit. I checked the thermostat and it opens as designed at 60 degrees C (140 F). I ran it today and I still have the overheating problem. When I got home I took the cover off of the PCV. and looked at it. Is there a way to tell if it is OK or should I just replace it. I think I was looking at the correct part. Am I correct that it is a round plastic piece with a X pattern located behind a cover under spring pressure?

[Sequoiha]

you are looking at the correct part, wat the plastic valve stuck or could you pull it out easily,,,

[rodbolt17]

did you replace the pump housing?

[SeaArk20]

Yes I did replace the housing.
No it did not seem to be stuck.

I it not the PRV I'm at a loss for what it could be

[SeaArk20]

I have a new question about my overheating problem.
The small nipple that is in front of the forward/reverse gear on the lower unit i think is the water pressure line. On my motor that nipple is not attached to anything. I notice on the diagram of my motor it is attached to a hose or if not in use it is capped off.
When I attach the motor to the muffs to run I notice water running out of the front of the lower unit i assume from this nipple.
Could the fact that the nipple is not capped be causing me to lose enough water pressure to cause the overheating at high speeds?

[ausnoelm]

I think you are talking about the speedo pickup!

[Sequoiha]

You are referring to the speedo nipple,, got a question for you though, are you sure the enigne is actually overheating, have you measured with a temp gun. you could be having a wiring or sensor issue.. just because the alarm comes on doesnt mean its hot.. something else, maybe the tube is plugged up from previous water pump parts, I just repaired an engine that the customer has had at 2 different shops, and i found 5 impellar fins in the top of the water tube at the base of the power head..