350 cooling problem

Well once again I humbly call on you folks for some advice...I have spent about an hour with the search and can't seem to find an answer...

This is a 1979CC pre alpha drive with a rebuilt engine 5 years ago..On this past Sunday it was running fine, I started it up on Thursday and got about a half mile and it overheated. I put it in neutral and revved the engine and it immediately cooled back to normal. I let it idle for a while and all was good so I went into gear and got up to plane (about 2200rpm for me) and it started to heat back up. so slowed down to about 1500 and the engine started to cool, went back up on plane and the temp started to climb....So I say to myself maybe the thermostat is bad so I replaced that today but no improvement. I disconnected the raw water hose where it goes into the thermostat housing, cranked the engine and I got a good flow, probably around a gal a minute just idling. Thus my confusion, the raw water pump was replaced 5 years ago and the boat has never been in salt..I guess what stumps me it that this came on so suddenly and it seems I have plenty of flow from the pump, I thought I would check in with you folks before I tear into the pump.........Thanks FB

Re: 350 cooling problem

5 years ago it 3 years too much. 2 years max using it or storing it. Start by inspecting the impeller . May have become de-bonded from the inner shaft or the vanes are "set" .

Re: 350 cooling problem

Thanks, Does anyone know how much the pump should flow volume/time?

Re: 350 cooling problem

A whole bunch more then a gal and minute. Probably closer to 10.

Re: 350 cooling problem

Ok,,, Thanks ..........I just changed out the oil in the drive a month ago...damn.....I was looking for the less obvious.........the open intake line looks like a garden hose, but maybe it ain't enough...............

Re: 350 cooling problem

Anyone have a recommendation on which brand of pump kit. Seems that Sierra and Mallory are the most common brands....

Re: 350 cooling problem

Well went and ordered a sierra kit. Got one more question for ya. I don't have a trailer so I will be doing this with the boat in the lift over water. I plan on working from a small flat bottom boat. the last time I did this I had the entire leg off sitting in the shop, this time I'm going to try just removing the lower end. Will anything fall out when I separate the two?

Re: 350 cooling problem

Rebuild kit will be here wed. I'll let ya know how it works out...and thanks for all the help.............

Re: 350 cooling problem

I got it torn down today, I decided to pull the entire leg and separate it in the shed..this way I can grease the u-joints as well...The pump impeller definitely had a set to it and the edges of the vanes were scalloped..The slinger was missing and I have no idea where it was but I think it probably went out thru the exhaust..anyway. now just waiting on parts..I won't wait 5 years to change it out next time.......Thanks folks.........

Re: 350 cooling problem

got it buttoned back up today..was reading the pressure test thread in the sticky section and was wondering how long you can expect the drive to maintain pressure.....? I've got a pressure test fitting that pipe fitters use to test gas lines in new houses and I think I can mod it to work on the outdrive. I didn't have any water in the oil that was in it but I figure it would be a good idea to do anyway...in case I messed something up putting it back together....

Re: 350 cooling problem

5 hours later the pressure is holding at 10/12 lb..........If I pump it up higher, it will bleed down a bit and then hold at 10/12 lbs....sure would like to know if this is normal............should I expect it to be the same in the AM..........

Re: 350 cooling problem

Well it lost a couple of lbs over night...What do you folks think?

Re: 350 cooling problem

I put the outdrive back on today and went for a short run...all seems well temp is acting normal......