VP 8.1 Gi-J 375HP not heating up

[paulowow]

Hello!
This engine has a new water pump, new impeller, new stat and has been totally cleaned and mounted after installing new head gaskets. It is now working perfectly apart from temperature that doesn't stop going to its normal temp (just below 175) and back down to almost 100. This started after replacing the water pump back in August.
Volvo Penta replaced the original stat (140) with an 160?, may this be causing the problem? Should I try and get a 140?
I would appreciate very much if you could help me with this issue.

 

[alldodge]

Howdy

What happened to the motor to cause the repairs listed?

 

[bruceb58]

I would be testing your thermostat out on a stove. Do repeated heating cooling cycles to make sure it doesn't get stuck open.

Or just replace it.

 

[Scott Danforth]

remember, a thermostat is the cheapest piece of wax capsul wrapped in the cheapest pieces of 304 stainless with the cheapest pieces of brass, sold for a maximum proffit with minimum expense.

I suspect your thermostat is sticking.

 

[bnicov]

Take off the thermostat housing, look at the passages VERY CLOSELY. Betcha a dozen doughnuts that there is a small piece of the old impeller in there. I have been there with my 4.3. New impeller as a maintenance item, new thermostat and and it would not heat up.

 

[jerryjerry05]

Sounds like the thermo's sticking??

I'd always heard that a motor that runs hotter, runs more efficient.

Gotta wonder why they started with a 140 then went to a 160???

Anyone have the bulletin?​

 

[Fun Times]

"VOL"VOPENTA. Volvo Penta of the Americas 1300 Volvo Penta Drive Chesapeake, Virginia 23320-9810
Distribution: Parts Date: Sept. 2008
~T 3856961
C> C)
Parts Bulletin
Group P-26-2
Number Version 1 01
Thermostat Replacement
Models: 8.1L, raw water cooled
Binder: Parts Replaces: n/a
Beginning with serial number 4012253241 the thermostat has been changed on current production of raw water cooled 8.1 L's
Thermostat 3856961 (160?) is now used for these engines. The thermostat was 3853983 (140?) prior to the change.
The new thermostat allows the engine to operate at the optimum temperature for the new GF4 engine oils specified for Volvo Penta gasoline engines.
3853983 was also used on all earlier raw water cooled 8.1 L production. Thermostat 3856961 should now be used whenever the thermostat is replaced on any 8.1 L raw water cooled engine.

^ the link below is broken here on iboats due to the vendors name but there's not much to see inside the bulletin other than the copy and paste above.
http://www.marine parts express.com/VP_Service_Bulletins/170%20%20%20%20%20%20%20%20%20%20PB%20%20%20G%20P-26-2%20%20%20N1%20%20V01%20%20%20%20Thermostat%20Repl acement.pdf


Unfortunately paulowow hasn't been back online since he made the original post. One question would be if his engine uses antifreeze or not. Most of these 8.1L engines do but not all. If it does use A/F then not to much can obstruct the "thermostat" itself debris wise from the lake water. Would be more of a heat exchanger blockage possibly among other things of course.
http://www.volvopentastore.com/Cooli...view_id.787284

This started after replacing the water pump back in August.

Another question would be what water pump? The sea water impeller or the engine block circulation pump ?.