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1988 260 5.7 L Jackshaft extension model overheating

T

torbau

Member
When running at higher RPMs (not idling) temp is fine but at idle or low rpms the temp gets up to 200F Normally runs at 160-180.
Does this model have an impeller in the out drive as well as a seawater pump on the engine? What is the most likely cause of this problem?
 
I haven't seen a forward engine w/ jack shaft for a few years.
I just now did a search.... I see that the forward located engine (with jack shaft) was used in front of the A and B drives, and possibly the old TR or TRS drives.
https://www.google.com/search?q=mer...GDQIHcvvBqQQ_AUIDCgD&biw=1440&bih=783#imgrc=_

The A drive needs an active seawater pump in order for the seawater path to provide cooling for the upper gear unit.
If your system also includes an engine mounted seawater pump, the A drive seawater pump supply can be diverted over-board.
Place the discharge port in a location that allows you to monitor the flow.

Just what are you doing?
Are you putting together a Forward located engine w/ jack shaft arrangement, or are you doing maintenance on a forward engine w/ jack shaft?

And yes..... photos would be helpful!


.
 
Look for a pump near the lower front of the motor. either driven by a bely or directly off the damper pulley.

Jeff
 
RicardoMarine said:
I haven't seen a forward engine w/ jack shaft for a few years.


Just what are you doing?
Are you putting together a Forward located engine w/ jack shaft arrangement, or are you doing maintenance on a forward engine w/ jack shaft?

And yes..... photos would be helpful!


.
Click to expand...

This is a boat that is in service and I am attempting to do maintenance on it for the overheating problem
 
torbau said:
When running at higher RPMs (not idling) temp is fine but at idle or low rpms the temp gets up to 200F Normally runs at 160-180.
Does this model have an impeller in the out drive as well as a seawater pump on the engine? What is the most likely cause of this problem?
Click to expand...

torbau said:
Yes it is a 1988 with an Alpha drive
Click to expand...

If the A drive pump has been circumvented and an engine mounted seawater pump has been added......... you will still want the upper unit cooling provided by the A drive pump. Pull the lower unit and see if the seawater pump is active!
 
RicardoMarine said:
If the A drive pump has been circumvented and an engine mounted seawater pump has been added......... you will still want the upper unit cooling provided by the A drive pump. Pull the lower unit and see if the seawater pump is active!
Click to expand...

I don't see an engine mounted pump and it appears there is a 3/4 " heater hose running from the drive to the power steering cooler which inturn connects to the thermostat connection point. I think there is an engine circulating pump but no other pump. There is a good chance that the drive pump is worn since the boat is 30 years old. I was hoping for something easier like the thermostat but that is unlikely.
Do the exhaust elbows require changing periodically? What would go wrong with them?
 
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