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engine rpm low when engine warms up

 
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dgrkmr57



Joined: 04 May 2011
Posts: 2
Location: Lethbridge Alberta Canada

PostPosted: Wed May 04, 2011 6:17 pm    Post subject: engine rpm low when engine warms up Reply with quote

problem: 4-170 merc When is cold it will get up to 4200 rpm as the engine warms up the rpm drop down to somewhere between 2500-3300 rpm. Repairs made: Fuel tank drained inspected and refilled with 91 octane fuel tank was clean. installed merc fuel filter/water seperator and have installed new filter. new fuel pump installed OEM pump. carb fuel filter removed blown out but was clean. butterfly valve on carb is wide open. flame arrestor clean boat has been run with out the flame arrestor made no change. thermostat was check tested it works just fine water temperture guage is showing 165 cylinder head water temperture fresh water pump has been rebuilt. new hoses on the fresh water system. The prop is the standard pitch and size for this setup Is it possible to have a problem with the cooling of the intake manifold ? What am I missing?
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Last edited by dgrkmr57 on Tue May 10, 2011 8:41 am; edited 1 time in total
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dgrkmr57



Joined: 04 May 2011
Posts: 2
Location: Lethbridge Alberta Canada

PostPosted: Sun May 08, 2011 8:47 am    Post subject: 4-170 engine RPM low when engine warms up Reply with quote

I have also put my boat on a boat dyno they they could not test the engine because it was running at 250 F closed water temperture. but the guage was showing 160 and the themostat is a 160
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