blackmax 150

[chadbenton]

I have an 88 150 xr2. Ran it today and it ran perfect. But, there is a temp. issue it has always had, and not sure what to do. Cruising at 5000revs. the temp. gets betwee 190 and 200 degs. My water pressure stays constant at 8 to 9 psi. I know the temp. sender is mounted between to cyls. on the head and is just a head temp. and not acutal water. What would normal operating temp. be. And should I remove the dolphins off the lower unit, can this affect anything.

 

[Chris1956]

Re: blackmax 150

Chad, that temp is a bit high. Are you sure it is accurate? If so, I would pull the thermostats and test them in hot water on the stove with a candy thermometer. They should open at 140*. Replace if necessary.

How old is the waterpump impeller? 9PSI is not very much for that motor. You might rebuild water pump. Check water pickup holes in lower unit and water passage under water pump base for cloggs. Lastly rebuild poppit valve on starboard lower side of block.

 

[chadbenton]

Re: blackmax 150

I did replace the water pump and the poppet valve last year, but never got to run it. The poppet seems to be leaking out of the weep hole on the muffs, so I will pull it and the lower unit tonight and verify any wrong doing by me. Will let you know what I found.

 

[kyfig375]

Re: blackmax 150

Could bad thermostats cause temp to be OK at idle and low speed but heat up at higher RPM's?

 

[hkeiner]

Re: blackmax 150

The water pressure readings at various RPMs can help indicate what the problem may be. If the motor is overheating at higher RPMs, then the thermostats may not be the cause as they primarily control water flow at lower RPMs. The below guide may provide some more ideas as to a solution. Good luck.

 

[chadbenton]

Re: blackmax 150

Thanks for all of your replies, some very helpful information. I just removed the lower unit, poppet valve and t-stats. Inspected everything, and the only problem i could find was the screw on the poppet valve was too long and bottoming out, leaving approx. 1/8in of play between the valve and the diaphragm and washer. Anyone ever seen this before. I trimmed the screw and now have a good tight fit. I also pressurized my pressure guage just to verify, and pressurized from the lower coolant tube, with t-stats and poppet reinstalled and it held pressure very well, with just a litte coming out of the tell tale. As a last resort I pulled off the dolphins off the ventillation plat, thinking this might also be affecting water flow. Plan on taking it to the lake saturday and see how she runs. If you guys think of anything I missed, please let me know.

Thanks

 

[chadbenton]

Re: blackmax 150

One more quick thing, with the lower unit off, there was dark sooty exhaust on the prop. shaft, and dont recall ever seeing this before, is it normal.

 

[chadbenton]

Re: blackmax 150

Just got back from the lake, with no change in water pressure or in temp. The only change was from removing the hydrofoil, made it a dog out of the hole, so its going back on. Water pressure still around 8psi at 4200rpm or so. Temp. still climbs , unless i back off on the trim and keep it deeper in the water. Removed lower unit again, and think I might not have a good seal between water pump and base. Gonna replace it all for good measure. But, prop shaft is covered in exhaust and shows signs of heat, this concerns me, what could cause it.

 

[chadbenton]

Re: blackmax 150

May have found a few problems. Inspecting water pump and found lower base is warped at one end, hopefully sucking air. Also while using the search I found a post that confirmed one of my thoughts. There is a divider plate between exhaust leg and water pump, it should be sealed with silicone, and have a good bead on top to completely seal of the water pump from any exhaust. Mine had no silicone on top and left an 1/8 in. gap, resulting in lots of exhaust flow into the water pump area, thus the soot on the prop. shaft. I had an evinrude before that had an actual gasket, dont know why merc. didnt, but oh well. So, I ordered a complete water pump assy., new t-stats, temp. sender and will seal off divider. Will hopefully get results in a week or so and will give an update.