engine temp and exhaust riser temp??? too hot?

dale332

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!! 

Liberty44140

Not sure on what would cause it, you need to figure out if you have a problem to fix first. Also did the temp drop while on plane or at idle? My temps climb while heading out the channel at idle and stop at 175 on the gauges, then while
planing they will come down a little bit. Back to 175 at idle coming in. Sure wouldn’t hurt to change thermostats just to be proactive, that’s easy, but I’d still get a laser gun to find out reality. 

dale332

Update- after pullingpower ateering cooler and visually inspecting I found there had at some point been water in power steering system which must have froze and swollen on the PS side which was restricting water flow but did not swell and bust. So at an idle it had enough water for everything to act normal but once engine was under a load at higher Rpm’s it just could pass enough water to keep it cool. Replaced cooler all is well now! 

skennelly

Why 2 posts?

dale332

My first time I didn’t intentionally do it I couldn’t find it and thought I posted in wrong place I apologize 

skennelly

Maybe thermostat.  Certainly worth changing to see.  If water is flowing clear I'm not sure what else it could be.

Liberty44140

Doubt that there is a problem. My gauges say 175 (I’m closed cooled), I’m sure it’s less, those gauges are crap. Probably 165. Before anything I’d go buy a laser temp gauge and shoot the exhaust when fully warmed up 

dale332

If I shoot exhaust what kind of threshold am I looking at? Anything below say 200?? What do you think cause it to begin with? Any ideas?

as far as engine temp 180 is no where near “over heating” however the fluctuate between low 100’s like 105-110 up to 180 and back down is concerning to me... thermostat make sense? I’ll probably change it regardless. Just looking for other ideas as well. Also, what temp thermostat should those engines have in them? Close cooled 5.7’s 

reneechris14

I shoot my risers all the time with the laser they stay around 100° to 110°. Motor stays around 170° ish that is the thermostat. Even when running you be able touch the riser for bit and not burn your hand. I have closed cooling  (horizon). The y pipe should not get hot enough to burn wires. 

dale332

Engine warms up while on plane and cools off fast while back down at idle.... maybe not a “problem” but something obviously isn’t perfect since the temp is fluctuating that much and the riser got that hot only 1 time tho.... - however thermostats will he changed on both engines 

the riser got hot enough that one time as described to burn thru the hoses and I checked and flushed everything I couldn’t find a problem... and it hasn’t gotten that hot since... that I know of? 

Cableguy Greg

Have you changed the impeller on the sea water pump? Sounds like it might not be getting enough cool water, or you might have pieces causing a blockage.

Dude_Himself

Impellor intact? Was the one removed previously whole? Sounds like you had something slowing/blocking the cooling water flow - if it's a sealed system with a heat exchanger it's even possible there was something on the pickup (hull or leg?). I've also read a lot of times the outdrive gets "coked up" with mineral deposits where it passes through the transom - easy to pull and verify.

dale332

Impeller was not intact when I replaced it was chewed up... I back flushed through everything quite a bit... I was thinking this was a possibility but since it kind of “fixed itself” I couldn’t verify. Boat is in slip and no trailer... you mean pull drive to verify? Or pull hose that connects to fumble housing? If this is clogged any recommendations on cleaning? No thru hull fittings on engines only gen and a/c and such. 

dale332

Don’t know if it matters but it’s been a fresh water boat it’s entire life also in Kentucky 

GMSLITHO

Here is a picture of the hose I just took out there was corrosion around the outside closing up the hose you can check it from inside but you need to pull the drive to replace it .hard to believe I wasn’t running hot

rasbury

Bravotitis!

dale332

at idle with hose off it seems as if i have plenty of water being pumped in thru sea pump?  guess ill keep checking stuff 

dale332

It’s a 2001 mefi-3 ECM I had to replace it when I bought boat