1999 200 Mercury EFI Cooling Water Path

[hodywvu]

I have 1999 2000 Mercury EFI SN: OG842008.

The motor has had an intermittent telltale for the past 3 years. I have replaced the water pump, thermostats, and poppet valve. Still have the intermittent telltale.

With the lower unit off I connected a hose directly to the water tube. With the motor not running water came out of the telltale, exhaust, and the cavity in the midsection that has the water tube and drive shaft in it. I did not think that water should be coming out of this cavity. I had thought that the water tube may be cracked or a corrosion issue/gasket issue on the exhaust plate. I pulled the power head. I thought the problem would be obvious once the power head and exhaust plate where removed.

When I inspected the 2 plates between the midsection and power head it seems that the motor is designed to have water coming out of the midsection cavity with the water tube and drive shaft in it.

Am I correct in this observation?

Also after more research it seems that the intermittent telltale is how the motor is designed. The telltale is after the thermostats causing the telltale not to be a steady stream.

I think I pulled the power head for no reason.

Thanks for any response.

[leonreno]

The tell tale stream does come from the thermostats, so no stream until it warms up and open the stats, the start to open at 143 degrees. In warm water they generally open fairly fast, less than a minute, in very cold water I believe they could open and close and cause an intermittent water stream. I don’t know first hand because the waters I fish are usually 60 degrees or higher.

it’s hard to determine anything going on with the water pump when hooked to a hose because the hose pressure can sorta override the pump and poppet valve’s normal operation. hose pressure Can easily over ride the poppet valves 9 Psi spring and open it up. The one thing you don’t mention and I would recommend is a water pressure gauge, it’s great at predicting a problem with the water pump (or other cooling component) before it causes a significant problem. You can watch for a drop in pressure at idle or when running and notice the pump is getting weaker.

[JOE54]

think so too that engine has to reach a constant 143 degrees before tell tale will be steady , heres a test take out theremos and start it bet its steady then, put um back in , needs it to alow water to absorb heat from mtr

[hodywvu]

Thank you for the replies.

To clarify, the telltale is intermittent and when it is working is not a steady stream. Sometimes it comes out more like a mist. This lead to to believe that I was getting exhaust into the cooling system. I do not believe it is a bad head gasket. They have been replaced about 2 years ago and I have good compression on all cylinders (120-125 psi). This lead me down a path of checking the plates and gaskets between the mid section and power head. I found that the rubber seal on top of the exhaust tube was not seeded correctly and pinched. It appears that it was not sealing correctly.

Once I get the parts to reassemble I will let you know if this fixes my problem.

I would still like to know if water is supposed to come out of the cavity in the midsection that the water tube and drive shaft are in?

Thanks,
Dave

[leonreno]

I’m pretty sure that is normal, the water exits the powerhead and fills around what Mercury calls a “wall of water” around the exhaust to keep the midsection cool, but it drains too.

[EuropeanAM]

There is water "everywhere" in that midsection when the boat is sitting in the water.

Make sure your LOWER gaskets (for the water pump) are intact with no tears, splits or broken pieces. Three (3) gaskets total that should be replaced when doing the pump.

And as stated above: Telltale comes from the thermostats, hence there is little (or no) water present until, or unless the t-stats are OPEN. And water will be PIPING hot when present (stream may come and go as thermostats open and close).