engine temp? riser temp? too hot???

dale332dale332 Member Posts: 23
ive read virtually every temperature related post in this forum that i could find and decided i would ask myself HELP!


Ive recently bought a 2001 340 rinker FV it has twin merc horizon 5.7s efi. Ive had it out about 3-4 times mainly testing things out and fixing as needed, boat has been in dry storage for two years so some things needed attention. 

After normal tune up (plugs,wires,filters,fluids etc.) and both fresh water pumps (housing and impeller) engines run GREAT. At intitial start up in slip stbd engine gets up to about 140 degrees and holds, port engine gets just a shade over 110 degrees or so. i come out of no wake zone and get on plane for the first time watching gauges constantly, oil pressure is steady around 40 lbs stbd temp is around 140 ish (factory gauges) port engine has climbed slowly to about 160,  i kept running didnt think to much about it since its closed cooled.. kept running on plane and it climbed to high 170's close to 180 and seemed to level off. This is after maybe 4-5 minutes on plane. i then smell a burning smell so i open hatch and the hydraulic trim line and bilge pump hose is melting against port side of Y pipe on port engine... i came back down to idle and shut engine down (engine temp still high 170's) i put a bit of bottled water on riser to see how hot it was and it IMMEDIATELY sizzled off. i limped back to dock with one engine. 

i pulled riser thinking it was clogged it looks practically new, i pulled hose connections at steering cooler and flushed with hose, i opened heat exhanger and flushed with a hose seemed clear, i pulled hose going into that side manifold ran water thru it. it was completely clear. I then ran water (slowly) up maniflold to make sure it was coming up into riser.. seemed perfect. At his point im pretty stumped. i start engine with manifold hose off had a nice looking flow coming out of it. reinstalled it... took boat back out. 

This time i got on plane and watched engine temp gauges and ran on plane for probably 20 minutes... no IR gun... just a hand and a bottle of water. port temp gauge climbed up to 180 again and maybe bounced over a tad but nothing i would be scared about. stbd still stayed consistently around 140 ish. while on plane with engine hatch up i laid my hand on riser that got so hot before. it was touchable. not for very long, 3-5 seconds maybe. water would evaporate quickly but not sizzle at all... i continued running boat for awhile before going back to dock... i noticed when i came off plane and got back to an idle speed in no wake zone the temp that was at 180 fell down to low 100's before i even got to my slip. 

are these issues related?

do i still have a riser temp issue? 

what should riser temp be roughly or what is "safe"? 

whats causing port temp to fluctuate so much? thermostat? 

any tips are extremely appreciated!! 
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