No flow through thermostat housing

[cowboyskiafan]

I think this may be a quick answer for you all. I have a 1976 Glastron CV-16 SS that runs great. Second season I've had it. Last year when I got it the engine was running hot. Changed the impeller and ran it all summer long with no problems. Took it to the boat shop to have it winterized and water was in the lower unit and it froze and cracked. Replaced the lower unit. Then, the ORIGINAL starter went out. Boat shop couldn't believe it was the original. Anyhow, did that, but before the starter went out, I had ran it a couple of times in the driveway and noticed it was running hot. I'm a do-it-yourselfer so I have troubleshooted the best I know how. Now I'm coming to you.
-New riser
-No pipes are clogged
-There is no leaking from the manifold or riser
- Impeller changed: Here's my question: The impeller I changed last year seems much lighter and skinnier than the one I had ordered for me this year. The serial number for the one last year had been superseded to the one I purchased. I believe the new one is 3107, but don't quote me on that one. Do I have the wrong impeller which is not allowing water flow? I hope I did not do anything wrong tonight but I took the thermostat housing off as well as both big hoses from the circulating pump and manifold. I started the engine with the muffs and ran it for maybe 6 seconds to see if there was any flow at all. There was none. I was expecting water to shoot at me, but nothing came out. Water shoots out of the back of the boat like nobody's business when everything is installed, but tonight with all that off, no flow from the front of the engine. I'm sure this is what's causing the riser to be super hot.
So... Impeller change, as well as the type of impeller? water pump in lower unit? What are you all thinking? I know this is very long but I want you all to know all the information. Thanks in advance.

 

[Bondo]

Re: No flow through thermostat housing

I think this may be a quick answer for you all. I have a 1976 Glastron CV-16 SS that runs great. Second season I've had it. Last year when I got it the engine was running hot. Changed the impeller and ran it all summer long with no problems. Took it to the boat shop to have it winterized and water was in the lower unit and it froze and cracked. Replaced the lower unit. Then, the ORIGINAL starter went out. Boat shop couldn't believe it was the original. Anyhow, did that, but before the starter went out, I had ran it a couple of times in the driveway and noticed it was running hot. I'm a do-it-yourselfer so I have troubleshooted the best I know how. Now I'm coming to you.
-New riser
-No pipes are clogged
-There is no leaking from the manifold or riser
- Impeller changed: Here's my question: The impeller I changed last year seems much lighter and skinnier than the one I had ordered for me this year. The serial number for the one last year had been superseded to the one I purchased. I believe the new one is 3107, but don't quote me on that one. Do I have the wrong impeller which is not allowing water flow? I hope I did not do anything wrong tonight but I took the thermostat housing off as well as both big hoses from the circulating pump and manifold. I started the engine with the muffs and ran it for maybe 6 seconds to see if there was any flow at all. There was none. I was expecting water to shoot at me, but nothing came out. Water shoots out of the back of the boat like nobody's business when everything is installed, but tonight with all that off, no flow from the front of the engine. I'm sure this is what's causing the riser to be super hot.
So... Impeller change, as well as the type of impeller? water pump in lower unit? What are you all thinking? I know this is very long but I want you all to know all the information. Thanks in advance.

Ayuh,.... Ya forgot to mention, what Motor, 'n what Drive,...

The impeller for the Alpha series(MC-1, R, MR, Alpha) of drive hasn't changed, so I'm guessin' ya mighta got the wrong impeller,...

 

[cowboyskiafan]

Re: No flow through thermostat housing

Ayuh,.... Ya forgot to mention, what Motor, 'n what Drive,...

The impeller for the Alpha series(MC-1, R, MR, Alpha) of drive hasn't changed, so I'm guessin' ya mighta got the wrong impeller,...

I'm sorry. All that info and I made a rookie mistake. It is a 120/140 Mercruiser 3.0. The drive is an Alpha 1 Gen 1. I was hoping you would reply Bond-o as I have used these threads countless times and you have given me valuable information.
The serial number of the impeller I changed last year is 47-89984-3. I looked it up to purchase another one and everywhere I looked, it had been changed to a new version. I'll look on this site again though.

 

[cowboyskiafan]

Re: No flow through thermostat housing

I believe this is the one I purchased. Like I said, it feels much thicker and heavier.
New Sierra 18 3017 Mercury 47 89984 Water Pump Impeller | eBay

 

[cowboyskiafan]

Re: No flow through thermostat housing

Figured it out. The water pump "stem" on the water pump (lower unit) that came with the lower unit, was not long enough. It was not reaching the hole in the upper unit to get water to the motor. I replaced it with my old water pump and it works great!

 

[Bondo]

Re: No flow through thermostat housing

The serial number of the impeller

Figured it out. The water pump "stem" on the water pump (lower unit) that came with the lower unit, was not long enough. It was not reaching the hole in the upper unit to get water to the motor. I replaced it with my old water pump and it works great!

Ayuh,.... The Number yer talkin' 'bout is the Part number,...
Motor's, 'n drives have Serial numbers that ya use to find the Part numbers of the parts,...

But anyways,...
You can push the water tube(stem) into the Upper, 'n Then stab the lower on, alignin' it with the pump housin', down low, insteada tryin' to hit the water pocket cover that can't be seen,...
The Stem(water tube) don't care where it starts, so long as it ends up in it's home,...

 

[Cord72]

Re: No flow through thermostat housing

Allow me to tag into this thread with a follow up question, same topic and same symptoms. 1991 Bayliner with 3.0 Mercruiser 4 cyl and sterndrive as well. Mine actually overheated on the water, up to 225F on the guage when we noticed the smells and shut it down, got towed back to the dock, but still starts and revs fine.

- No water coming from the fresh water supply line when removed at the T-stat and started, in lake or on hose/muffs.
- I figured I lost the impeller thus the overheat, so I replaced it
-- New impeller from online purchase, confident it is the correct size and model
-- New plate and gaskets came with it, plus purchased a new guide sleeve, installed all, confident I hit the hole with the supply pipe hitting into the guide sleeve
-- New impeller key installed for good measure at the same time
-- Torqued to specs, re-installed, new oil filled per lower unit pump-in process

Testing in driveway:
- Removed supply hose at top of t-stat, started engine with water on muffs, but no water coming up through the fresh water supply hose up at t-stat end.
-- HOWEVER -- Water is pouring out of the prop, much more than i ever remember on past driveway tests.
-- The only piece I didn't replace is the supply tube in the bottom of the upper unit, but it did pull it down, hold it in my hands, then pressed it back up into place before installing lower unit again.

Assuming the impeller is pushing water since it is brand new... why would so much water be pouring out of the prop exhaust at idle and at rpm?
- If the supply line was clogged somewhere before the thermostat, wouldn't the water spray out the side of the rubber hose-muffs?
- If I somehow installed the impeller pump with the wrong rotational flex on the fins, the water still shouldn't pour out the prop, should it?

I'm perplexed...Any ideas are appreciated

 

[Bt Doctur]

Re: No flow through thermostat housing

check the connector hose at the outside of the transom,betting it off the fitting.Only other way out the exaust is that you missed the connecting tube completely or the water pocket cover was obliterated from the overheat.Water is just dumping down the exaust cavity.