Mercruise straight 6 I/O, another engine running hot

[SeaRay_SRV_180]

Hi guys,

Please go easy on me. I'm new to this and this is my first boat. To get you up to speed, I have read the other similiar posts regarding mercruise overheating issues. I have so many questions and no boat friends nearbye so I'm crossing my fingers here.

1970 SeaRay SRV180 inline 6 (160hp) Mercruise I/0

I bought the boat from a mechanic who replaced the following to supposedly fix the hot running engine. He said the engine ran cool for 30 minutes after he replaced these, but when I put it in the water yesterday, the temp needle went to the red line in less than 10 minutes.

he replaced:
- outdrive water impeller
- thermostat replaced at the front of the engine

The engine runs smooth so we can hopefully rule out a bad engine. Do any of you have any .pdf files showing an exploded view of the engine and outboard? I've worked on old cars for years, so I'll get it if you describe to me the things I should check, but I need some pictures for reference.

I've read the posts regarding overheating so here is what I'd like to check, but need some pictures to get my bearings:
- One thread mentioned ignition timing can affect temp. I've got a timing gun, so I need a clear picture of where I point the gun on this motor.

- One thread mentioned checking water flow from the outdrive into the engine to verify the impeller is good. I have to disconnect some hose to the engine and run water with the garden hose to verify right? Any pictures of what that looks like?

- One thread mentioned Thermostat on the engine. After this engine was ginving the previous owner trouble he removed the thermostat and ran the system wide open... If there is no siezed thermostat stuck half open, theoretically the maximum cooling power is being delivered... Right?

- One thread mentioned Water Pump... where the hell is the water pump on this engine? The belts look snug so let's jump over that step

All thoughts, pictures, step-by-step instructions would be most helpful. So much information to sift through and all I want is to have my boat in the water and running for the 4th of July. Feel free to e-mail me directly.

jason_bodenheimer@hotmail.com

 

[HT32BSX115]

Re: Mercruise straight 6 I/O, another engine running hot

An engine that has had the thermostat replaced and the raw water pump replaced usually has a blockage probably due to raw water pump remnants stuck somewhere down stream of the raw water pump blocking flow of water.

The pieces could be anywhere.

Also I'm not sure I would believe that the raw water pump is still not at fault. If someone, after that mechanic replaced the pump, ran it without water even for 30 seconds, It could have destroyed the pump and the (usually plastic) housing. So unless you have personally replaced the pump. I would look there first.


Regards,


Rick

 

[180shabah]

Re: Mercruise straight 6 I/O, another engine running hot

Like Rick said, start with the raw water pump. Here is a great tutorial on it's replacement.
http://www.mercstuff.com/waterpumpinst.htm

Your engine has two water pumps. A raw water pump is located in the bottom half(lower unit) of you outdrive. This pump is plastic with a rubber impeller that needs to be routinely replaced(every other year, unless damaged). It sucks water out of the lake, river, etc. and pumps it up to the circulating pump, located in the front of the engine (just like on a car). This pump is all metal and rarely goes bad.

 

[SeaRay_SRV_180]

Re: Mercruise straight 6 I/O, another engine running hot

Thanks for the information. If I'm going to dissasemble the lower-outdrive to replace the impeller (made of plastic, wow, could we've made it out of a crappier material) is there a kit that I can order overnight from this website? What would be the part number to purchase the unit when I'm ready to put it back together?

Thanks!
Jason
jason_bodenheimer@hotmail.com