1978 Mercruiser 898 Cooling issue

[BlueBayouV8]

Ok.. So this is my first I/O. It is a 305 Chevrolet V8, Somebody before me took out the thermostat and i have not replaced it yet because, i cant imagine that causing it to overheat.. Anyway. I have checked all the passages, and they all seem to be clear. I took off the main hose from the impeller to the engine, and there is a healthy stream, so i know the impeller is good. I took off the hose from the thermo housing to the water pump, and I have a good flow coming out of the housing into the pump. while running, i have a small trickle of water coming out of the port side exhaust outlet, and none out of the starboard side. The temp continues to climb till it gets to about 195 and then i shut it off. and i get steam from the exhaust (still just the port side). It seems to run the same all the way through. When i rev it i get some spray from the starboard side, bit not much.. When it got hot, after i shut it off, i did get a good flow of water out of both ports. (maybe about a gallon before it stoped, and it was hot! Please help!!! I want to take it out before the end of the season...

 

[BlueBayouV8]

Re: 1978 Mercruiser 898 Cooling issue

I took off the elbows and flushed them out.. They are clean... Why are there restrictor plates there. They have a very small hole on them... very very small. I removed them for troubleshooting, and nothing. very little water coming from exhaust. I have since put them back in. I did check again on the flow from the raw water pump. it is pretty weak at idle.. i have had the lower unit off, and the impeller looked good. i have back flushed the raw water line, and its clean. Could it be something with the impeller housing, maybe not sealing correctly? Im open to anything at this point. it seams to have a better flow when the rpms are up, but it doesnt run any cooler when i run it higher than idle.

 

[Bondo]

Re: 1978 Mercruiser 898 Cooling issue

Ayuh,... Change the Impeller,+ replace the T-Stat.... Then try it...

 

[BlueBayouV8]

Re: 1978 Mercruiser 898 Cooling issue

I think im gonna pick one up. When i took it apart the impeller looked good, but the housing looked like it was melted a little, an the seal looked kind of crummy, ill get new seals and try that. thank you

 

[meesh]

Re: 1978 Mercruiser 898 Cooling issue

If the housing looks anything but perfect, replace it.

 

[BlueBayouV8]

Re: 1978 Mercruiser 898 Cooling issue

I have found the whole impeller repair kit online for $35.. It comes with the impeller, lower and upper housing, all gaskets, and seals.. Im going to try to get it local first, is there anything else i should look at while i have it apart.. is there is good way to line up the shifter.. it was a ***** last time..

 

[BlueBayouV8]

Re: 1978 Mercruiser 898 Cooling issue

why are the restrictor plates in the exhaust? and. does anyone know the stock horsepower on this engine.. the tag is worn off.

 

[greg82255]

Re: 1978 Mercruiser 898 Cooling issue

The stock horsepower for your 1978 mercruiser 898 is 198 horsepower at 4200 rpm. I had the exact same motor in my checkmate before I upgraded the carb and exhaust.

When I disassembled the old exhaust, I also noticed the restrictor plates , and cannot figure out why they are there.

 

[Bondo]

Re: 1978 Mercruiser 898 Cooling issue

why are the restrictor plates in the exhaust?

Ayuh,... Those are the Shutters,... They stop any backwash from drowning your motor....