No water flow to heater at idle (96 350 mercruiser)

[saltwater_cowboy]

There is no water flow to my heater on my maxum when the engine is at idle. Once up to 1200 rpm then the flow is fine.<br /><br />I've checked the raw water pump impellor today and it looks good as new. <br /><br />Any suggestions?

 

[Don S]

Re: No water flow to heater at idle (96 350 mercruiser)

Is your engine raw water cooled or do you have a closed cooling system (Heat exchanger with antifreeze).

 

[saltwater_cowboy]

Re: No water flow to heater at idle (96 350 mercruiser)

Raw water cooled.

 

[Don S]

Re: No water flow to heater at idle (96 350 mercruiser)

It's difficult at best for those heaters to work on a raw water cooled engine, you may have some flow but not enough for any heat just do to the design of the system.

 

[rob935]

Re: No water flow to heater at idle (96 350 mercruiser)

check your thermostat it may be dodgy..

 

[Don S]

Re: No water flow to heater at idle (96 350 mercruiser)

"dodgy"??????

 

[saltwater_cowboy]

Re: No water flow to heater at idle (96 350 mercruiser)

The engine gets up to and stays at running temp fine its just there is little to no water being pushed round the heater circuit at idle which seemed strange to me.<br /><br />On my last boat with a 351 ford there was loads of water puched round at idle.<br /><br />I did think maybe it could be the engine circulation pump but the engine is mint and only done 240hrs. There are no tell tale noises from the pump so didn't think it was that.

 

[Bondo]

Re: No water flow to heater at idle (96 350 mercruiser)

Where,... Exactly is the Heater plumbed Into the Engine,..????.....

 

[jch7450]

Re: No water flow to heater at idle (96 350 mercruiser)

FOR DON:<br />dodgy adj. If something or someone is described as dodgy, this means that they are either shady ("I bought it off some dodgy punter in the pub"), sexually suggestive ("The old bloke in the office keeps saying dodgy things to me at the coffee machine"), or simply not quite as things should be ("I got rid of that car; the suspension felt dodgy").<br /> <br />Just had to to let ya know. I use to work with a brit. and i'll tell you, I,v heard all kinds of different sayings.......

 

[saltwater_cowboy]

Re: No water flow to heater at idle (96 350 mercruiser)

Out of the top of the inlet manifold, into the heater and then return into the water pump, at least I think. I'll have to double check.

 

[Bondo]

Re: No water flow to heater at idle (96 350 mercruiser)

That sounds Right,.....<br /><br />Has it worked before at Idle,..??...<br /><br />Pull the hoses from the engine,+ Blow thru them in the right direction, with your breath,.....<br />There should be Very Little restriction......<br /><br />Be careful of the Out-bound hose,... There'll be some Water........

 

[Boatist]

Re: No water flow to heater at idle (96 350 mercruiser)

Engine circulation pump sucks water thru heater on all the one I have seen. If it Sea water cooled or not I would pull both hoses to the heater and back flush it. Could have some rust and scale blocking the heater core flow. Back flushing will would force it out so you can have normal flow again.