Overheating issues Mercruiser 3.0 Alpha one gen 2

[Burning$]

Looking for some troubleshooting help/possible issues that are causing overheating. The guy I got it from said it needs some basic service and the water impeller changed. I got the water impeller changed. Took it for a water test at local lake. It will idle in neutral at about 160. Put it is gear at a low speed it will climb to about 200-215 with a few mins. Give it anymore throttle and it hit 225 quick. Put back in neutral and it won’t cool down. Only way I found to cool it off is to turn it off for about 1-2mins. Start it back up and temp will drop rapidly to around 160-175. Put it back in gear at low speed and just start climbing back to 200-225. It appears there is plenty of water coming out the back of it.

Boat: 2008 Bayliner 175

Engine Serial: 1A020364

Stern drive Serial: 0W889565

 

[skisky89]

I'd replace the thermostat! You can remove the thermostat and see if you still overheat (it'll just take a while for the engine to heat up) but Tstat's are cheap and easy to replace. Also check the circulation pump for weeping and a wobbly pulley.

 

[tpenfield]

There should be a power steering fluid/oil cooler at the rear of the engine. take the input hose off to see if there is a bunch of stuff clogging the water flow.

 

[Burning$]

Plugged to cap off to the thermostat and there was no thermostat installed. Ran water with a garden hose through the water pump and had good flow through the block. Ran water through the manifold and didn’t seem had much drainage out the back. Not sure if that has to have more pressure behind it to force water through it. Might have to make an adapter for garden hose to hook up right there. So maybe I have hot engine water that can’t escape fast enough to get new water circulating.

 

[Burning$]

Well I hooked up a garden hose to the manifold inlet line and turn the hose on. Had health stream of water come out the bad. Checked the inlet line coming from guess that’s the power steering cooler; no clogs. Inlet line to thermostat housing to lower unit had good flow. So everything appears to be getting flow. No wobble on the engine water pump when it’s running. Guess I’m back to the impeller.