blackmax 200hp 1987

[kegzzz]

can any one help me<br />i have a 200hp black max with a weird problem,it overheats on wide open throttle.<br />as you increase the throttle speed you can watch the temp guage go up in simulation with the rpm<br />then on wide open throttle for about 3-5 miutes the over heat alarm comes on , as you pull the throttle back the temp guage comes down.<br />i i leave it on throttle to 4200rpm the guage reads at the highest but no alarm.<br />i have replaced the head gaskets, the therostates to 120degrees, lifted the power head and checked under the passages all looks good.<br />i have fitted a new water valve on the side of the block,it has a new temp sensor and guage,<br />i have also cut the spring down on the water piston on the side of the block no different.<br />i have also removed the exhaust plate and checked this for blockage.<br />please help anyone

 

[phatmanmike]

Re: blackmax 200hp 1987

IS YOUR MOTORS INTAKE WATER HOLES ON THE LOWER UNIT BEING BLOCKED AT HIGHER BOAT SPEEDS? ARE THEY CLEAR? HOWS THE CONDITION OF YOUR Water pump? whens the last time it was changed? did you change it recently and forget the impeller key? do you have a fishfinder /sounder/ transducer that could be spraying water away from the motor at higher speeds? is yuor engine mounted too high on the transom? hows your water pressure at these higher rpms? could i ask any more questions?

 

[andy6374]

Re: blackmax 200hp 1987

kegzzz-<br />Well you did all the "hard to do" things already, so lets do it simple now.<br /><br />-Lets try a water pump rebuild. New everything.<br /><br />-New pressure relief valve assembly (poppet,spring,diaphragm, grommet...etc).<br /><br />Also pull out those 120 deg. t-stats and while the tstat cover is off, drop the L/U, and stick a hose down the tstat holes. Watch for any falling debris coming out of the water tube. Then stick the 143 deg tstats back in.<br /><br />keep posting and good luck

 

[kegzzz]

Re: blackmax 200hp 1987

hi to all that has tried to help<br />thankyou.<br />i have fitted a new water pump,with the thermo stats in the water pressure to me seems low when on a engine flusher.<br />with the theremos out the water pressure is very good, about two meters compaired to 1meter,also there is nothing at the back of the boat to affect water flow.yes the water pick up is very clear.again thankyou

 

[andy6374]

Re: blackmax 200hp 1987

Keep the tstats in.<br /><br />With the muffs on the water pressure will be low. You never said if you replaced the parts of the pressure relief valve assembly or not. Because, if the poppet isn't seated properly or is stuck open at idle speeds you won't have enough water pressure and you'll overheat.<br /><br />Did you use some form of liquid gasket between the waterpump housing and its mating surface (i.e. a gasket)? They can suck air sometimes.

 

[kegzzz]

Re: blackmax 200hp 1987

hi to all that is helping me.<br />yes i have fitted a new water pumpand to be really sure i fitted another pump again.<br />i replaced the water pressure valve all new parts geniune.<br />i also have checked the water pressure at full throttle it is very good,i have also pulled the water hoses off the heads and gave the engine a rev and the water shot up about 5meters in the air.there is plenty of water pressure for sure.<br />thankyou

 

[kegzzz]

Re: blackmax 200hp 1987

hi to all that is helping me.<br />yes i have fitted a new water pumpand to be really sure i fitted another pump again.<br />i replaced the water pressure valve all new parts geniune.<br />i also have checked the water pressure at full throttle it is very good,i have also pulled the water hoses off the heads and gave the engine a rev and the water shot up about 5meters in the air.there is plenty of water pressure for sure.<br />thankyou

 

[KCLOST]

Re: blackmax 200hp 1987

Ok,<br /><br />You say you have good water pressure at high rpms... You have replaced most everything that could cause your problem.<br /><br />First let me ask you what your water pressures are.. What does it read at idle, 2000 rpms, 3000rpms and WOT which is probably somewhere around 5500-5800 rpms?<br /><br />Speaking in psi numbers, you should see around 20-22psi at WOT. If you are seeing numbers higher than that even at 4200rpms you have a problem with the poppet valve not opening at rpms above 3000 or so. I know you replaced everything but it may not be operating properly.<br /><br />The poppet valve (pressure relief valve) must open at higher rpms to increase the "flow" of water circulating through the block and water passages. If it is stuck closed the water pressure will be high, but there won't be enough flow of cooling water. Without the increased flow, the water will be "stuck", for lack of a better term, in the water passages too long and it will absorb excessive heat to the point of tripping the alarm. And this means the engine is obviously overheating.<br /><br />One more thing, there may be a clogg in the exit port for the poppet valve, check for debri!<br /><br />Let us know!