Assistance on Mercruiser 160 HP Stern Drive

[Jack Stotts]

I have a rather old Mercruiser Stern Drive (1967 160 HP Chevy in-line 6). When ideling ,with little or no forward movement, the temp tends to rise then after getting on plane, it cools down nicely. I guess it's time to replace the impeller. The impeller is in the top of the gear foot which is bolted at the bottom of the main downhousing. When I seperate the gear foot from the top portion of the housing will the lube in the top portion of the down housing come out and make a mess? I can handle the mess but was just not sure if it will drain out when the two parts come apart.

[garland powell]

160 merc

hi,it will drain out but all you need to do is drain it befor you take it apart.Take the lower drain screw out than the top side vint screw and it will drain into a pan.No mess

[Jack Stotts]

Hey Garland, should I remove the out drive from the boat transom before I take the foot off of the downhousing or leave the unit attached to the boat and simply remove the foot? By the way, thanks for the previous info.

[Fast Jack]

MR drive

You may want to see if the manifold / riser is the problem, if the system is raw water cooled. Pull the block drain plug and let the water from the block run into the bilge ( hope you have a pump) ,if the engine runs at normal temp you may need to replace the manifold. Also you can pull the intake hose from the thermostat housing and check the water flow at low speed --should flow like a garden hose set to drink from.. good luck

[ricochet112]

A 160 Mercrusier "MOST" likely has a separate upper and lower oil cavity. If you have a vent/level oil plug by the cavitation plate, the split line, (there also may be a flush plug close by), then you have 2 separate oil cavities and won't have to drain oil before removing your lower unit.

Replace the COMPLETE pump kit, with a problem like yours, the housing may look OK but even the smallest warping will cause idling overheating.

Another place where they have problems is the riser (elbow) to manifold. Rust plugs up the passages between the 2 and wont let enough water flow, but thats more of a high speed problem than idling issue.

[JBM]

Another problem may be that the bell housing is corroded thru in the water passage. It may be worth taking the drive off at the six nuts holding it to the bell housing to inspect, especially if its had any history of running in salt water.

[ricochet112]

Another problem may be that the bell housing is corroded thru in the water passage. It may be worth taking the drive off at the six nuts holding it to the bell housing to inspect, especially if its had any history of running in salt water.

This is just good regular maintenance in general, greasing drive shaft splines, etc.

PS, don't forget to shift it into forward gear before removing the outdrive, and leave it in forward for installation also. You may also have a reverse lock down lever that needs to be in the release position also.

PSS, if you have 2 small shocks above the hydraulic rams, "TRY" to remove them first before attempting any other nuts/bolts, the shocks can be a real pain to get off.

This should be step 2 (or 3) AFTER replacing the complete pump kit.

[Jack Stotts]

Found the impeller to be hard as a rock and curved back so far it was almost useless. Well the new one is in and all is well. Thank you to all that provided the fixing advise. I went to the library and found a maintance manual which also helped greatly. It has been 20 some years since the impeller was replaced but then I've only put 425 hours on this boat in 40 years. Age alone is bad on impellers. Thanks to all again! Now I have to concentrate on getting ready for Ocoee.