84 Black Max 150 runs hot at full throttle

[wimico]

Motor runs at normal temp when run at 3500 rpm or less. Anything over makes motor run hot. New water pump (pressure is maxed out), rebuilt poppet valve, new thermostats, new head gaskets. Installed new temp gauge with new sender attached to port side. The overheat light is wired to sender on starboard side. At wot the gauge reads around 170 but the light comes on. Is it possible for the starboard side to overheat and the port not? When throttled down, the engine is steaming but quickly cools off.
Ideas?

 

[quicktach]

Re: 84 Black Max 150 runs hot at full throttle

How consistent is the water flow from the P line ? Getting any cavitation/air hitting the water pickup at WOT ? When was the water pump last serviced - could have broken impeller parts.

 

[Dukedog]

Re: 84 Black Max 150 runs hot at full throttle

(pressure is maxed out)?

Explain...........

 

[bajaunderground]

Re: 84 Black Max 150 runs hot at full throttle

How's the Telltale look? Is it a constant stream or little spurts? Could have some blockage due to a previous impeller issue? Just cause you have pressure doesn't mean you have flow!

 

[wimico]

Re: 84 Black Max 150 runs hot at full throttle

Water pressure gauge reads 15 psi at max. When running the pressure is at max. Haven't noticed p stream as constant or spurts but I will check today.

 

[Dukedog]

Re: 84 Black Max 150 runs hot at full throttle

Gauge only reads 0 ta 15 lbs? Was this tha case "before" all tha parts were replaced? Anything changed, ie: motor height? If it didn't do this before tha parts need ta check new poppet stuff install. Especially tha plastic disk if ya used tha old one. They tend ta warp and not do right. Other than that ya may have a blockage somewhere, gasket outta whack etc.............High pressure is usually air, blockage, poppet or any combination of these.................

 

[Texasmark]

Re: 84 Black Max 150 runs hot at full throttle

Son's 150 had pee plumbed off stats meaning stat had to be open to get pee. Pee poor design if you ask me. Unless the engine was hot and below 2500 rpm pee would come and go with the stat opening and closing and you had to wait for it to open on a cold engine before you got any pee. On his engine the bypass valve was at the center of the engine and below the powerhead fed by a tube from the top rear of the block without regard for left or right bank. Stats were one in each bank but were bypassed at around 2500 rpm by water pressure opening the bypass valve. Agree that just because you have water pressure doesn't mean you have flow.

Mark

 

[James R]

Re: 84 Black Max 150 runs hot at full throttle

If the motor is using the Mercury oil pump system it could be a lubrication problem. Simple way to check is to run the motor from a jug or tank of 50:1 premix and check the temperature.
If the bypass system is not working this will cause overtemp at higher RPM. Quite common.

 

[Dukedog]

Re: 84 Black Max 150 runs hot at full throttle

Tex, here's ya dia. of tha coolin' system. Tha hose from tha top to tha poppet was put there ta relieve air pockets in tha block/divider plate when tha water cooled reg. came out.............Besides tha '84 shouldn't have that hose anyway.

 

[Texasmark]

Re: 84 Black Max 150 runs hot at full throttle

View attachment 215527Tex, here's ya dia. of tha coolin' system. Tha hose from tha top to tha poppet was put there ta relieve air pockets in tha divider plate when tha water cooled reg. came out.............Besides tha '84 shouldn't have that hose anyway.

His was different as you said. His pee was plumbed off the stat cover and stats had to be open to get any water out other than the miniscule bypass water. In that diagram, it appears that you wouldn't have much if any pee if the engine was not over 2500 or whatever the number is for that engine to force open the pressure relief valve. Seems only water available would be from the stat bypass or stat and then it would have to compete with the drain which probably has less resistance meaning there would be no pee at the lower rpms. Confusing.

Mark

 

[Dukedog]

Re: 84 Black Max 150 runs hot at full throttle

It is but it isn't. Know production coolin' is confusin' (reason I like tha HiPerf coolin') but it does work..........Will add though that if stats are open and pump is up ta snuff ya "should" have a decent stream at idle or wfo but if poppet is "stuck" open then tha idle part may not be so much. Its all goin' down tha can, out tha gear case.

 

[out 2 launch]

Re: 84 Black Max 150 runs hot at full throttle

If you verify that the cooling system is functioning properly and still have a problem check the fuel system/carburetors. A lean mixture can cause overheat regardless of the cooling system especially at higher power settings.

 

[quicktach]

Re: 84 Black Max 150 runs hot at full throttle

Are you using the correct oil for the engine ....and getting enough of it ?