Black Max 200hp cooling problems please help

[Thecol]

1987 merc. 200 blackmax. i have changed impeler and all water pump gaskets,Thermostats and hoses. Is there any thing else I should change?. Old impeler was pretty tore up. I am fairly sure I got most of it out. Water is pumping but not as well as it should be. Motor runs well at idle about 195 to 200 degrees. Once the motor reaches 1000rpms temp goes right up 240 degrees.I bought the motor used so I have been taking it easy trying to get it straight.Water from the telltale (pisser) is very hot.Any information would be greatly appriciated.Thanks.

 

[85merc200]

Re: Black Max 200hp cooling problems please help

240 degrees is way too hot,what are you using to measure temps ?

 

[Thecol]

Re: Black Max 200hp cooling problems please help

Hello 85merc200, thanks for reading the post. I have used two different temp guages. One was a sunpro for outboard motors and I also used a tempo I\O guage with a 240 sending unit on the left head by the number one cylinder.<br /><br />The motor runs at 195 to 200 at idle and increases to 240 after about 4 miles and hour and then will drop back down to 200 when I release the throttle.<br /><br />I know the motor is running real hot. What temp should it be running at? No more than 200 I would think.

 

[trumanlake]

Re: Black Max 200hp cooling problems please help

By chance have you done a compression check on all cylinders? My 200hp had a blown head gasket on #2, which caused an overheat. Still had good tell tale and good pressure.

 

[gss036]

Re: Black Max 200hp cooling problems please help

Sounds like maybe a piece of the impeller is plugging something up. My motor is a 1989 200 HP. When I talked with my mechanic today about changing out the head gaskets (3 years is max he recommends for saltwater usage) and pump after 3 years, he was telling me the motors run rather cool at full to 3/4 throttle as the water pressue should be about 22 lbs and moves a lot of water through the block and heads. Normal temp at idle should be 143 degrees. Less than that at higher RPM's. Must be what the thermostats are(143). So, if you are running around 200 degrees, you have a problem.

 

[Thecol]

Re: Black Max 200hp cooling problems please help

i have not tried compreesion since i bought the motor.it probably sat for a longtime.and now that i am running it blew the gaskets?i was thinking that also.how much do head gaskets run?also will i be able to check for peices of the old impeller?

 

[Thecol]

Re: Black Max 200hp cooling problems please help

i am new to outboards so i dont know a whole lot.i do have i/o experiance.lower units seem about the sameso i know pump is done correctly.i have not seen any water spray from exhaust ports is this normal?

 

[85merc200]

Re: Black Max 200hp cooling problems please help

gaskets run about 31 dollars each, make sure you get a torque wrench and use the correct sequence to tighten

 

[Thecol]

Re: Black Max 200hp cooling problems please help

my buddy has a torqe wrench.i will be getting on that soon.what temprature should i be running when the boat is underway?my manual does not say.if my gaskets were bad sholdnt the plugs be clean?my plugs are nice and oily .this motor is oil injected would any of you guys change to premix or are they pretty trust worthy?i want it to last for along time.thanks guys.

 

[jim dozier]

Re: Black Max 200hp cooling problems please help

You might try removing the thermostat housing and thermostat and the lower unit and back flushing the engine by stuffing a garden hose into the thermostat housing. Put a bucket underneath the impeller pickup tube and see if any pieces of impeller or other crud flush out. Also while you have the lower unit off again, check the grommets on both ends of the pickup tube. In some engines the grommet at the top can pinch over and block the tube and flow.

 

[AndyL]

Re: Black Max 200hp cooling problems please help

Just a thought but you should check the poppet valve as if any crud is stuck in there the water pressure in the head would be lost. Be wary of running it at the temps you are talking about as you could cause expensive damage to the motor. I reckon you should see abot 145 degrees at normal running, maybe up to 170 at idle with low water flow.

 

[Thecol]

Re: Black Max 200hp cooling problems please help

where is the poppet valve?what shouldi be looking for .does any one know if water should be spraying from the exhaust ports.because it does not i was wondering because ive seen some that do. could that be it?thanks