Overheating issue

[heysange]

I have a '06 70HP Suzuki that does what seems to be a failsafe partial shutdown when it gets over 5,000 rpm's. (Engine starts missing badly and temp light comes on) I can let the motor idle for a few seconds and gently ease back up to full speed and everything is fine as long as rpm's stay below 5k. Mechanic has replaced water pump and thermostat and he doesn't know what else to do. This problem can happen just minutes after starting the motor and getting boat up on plane, so I don't see how the engine could actually be overheating. Didn't know if it's a bad sensor. Any ideas?

[noelm007]

First thing you need to do is find out if it is over heating, at 5,000RPM, it will get hot very quick, don't be fooled by the time factor, there is a couple of things to look at if it is getting hot, corrosion/blockage in water passages, head gasket, has the water pump been replaced correctly? was an entire kit fitted or just the impellor? lots of possibilities here.

[keakar]

that is usually a sign of a weak impeller that cant keep up water pressure at high rpms but since it was changed, "assuming" the water pump was installed correctly and the housing was in good condition with no scratches or wear marks then i suspect you have corrosion buildup in the engine passageways (most likely around the head water jackets) not allowing enough flow at top speeds and that would require you pull the heads off to acces them for proper cleaning.

little curly flakes of corrosion can build up in there and end up looking just like a brillo pad so water still flows, just not enough at full speed to prevent overheating.

[max007]

Giday heysange
have you worked out the problem with your motor yet? - I have a 2006 50 hp suzuki with exactly the same problems you have described

So far they have checked sensors, water pump and changed impellor but no change. Next step is to remove head to see if a blockage is present but the labour bill is over $1000 for this next step

Any other hints welcomed

thanks

[deano68]

i also have this problem with an 06 df40..the alarm is from the sensor on the exaust manifold, have had my mech look at it, and is diagnosed at "no failure".

he seems to think there mabe a bit of anode or forign matter upseting a water relief valve , will be getting it looked at on the 19 / 4th next week...

will let you know if this was the problem..
cheers, deano.

[max007]

hi Deano
Just got my boat back last week - cost $1176 to fix blocked engine passageways. Had to remove head to fix. Mechanic suggested it was more likely due to lack of use. Hope your problem isnt the same
max

[Harper]

I tend to agree with noelm007 and keakar....the overheat alarm system activates not only in situations of actual overheat, but also measures heat rise vs. time, to indicate that it is heating up so fast that there is a problem indicated. The alarm is set up this way to preclude damage to the engine before the situation gets too bad. So my guess is that there are likely some blockages forming that are starting to cause you problems.

[deano68]

hey maxx, yep hope mine isnt that costly, i use my boat very regulary and is serviced regulary also...fingers crossed.

yes harper, the computer sensors the temp rise in gradients, if it gets to one faster than it should you get the alarm and it goes into limp mode...so yes a slight blockage someware...
my mechanic seems to think he doesnt have to take the head off to flush the water jackets....lets hope..