Logo
FULL SITE MENU

2004 150 Saltwater overheating

B

Bubbco

New member
My 150 saltwater is overheating. If I am running at low RPM's ( barely planing...with motor under a lot of load) the heat buzzer will sound I can stop and put the motor in nuetral and it will cool down. I have replaced the water pump last year. the tattle tale stream is very very hot but don't seem like there is much pressure......What do I do next????
 
Did it run fine after you replaced the water pump? You might want to just check the impeller for wear.
 
Did you do the whole waterpump or just the impeller - if it was just the impeller get a waterpump "kit" and do the seals and gaskets as well.

Also confirm you don't have blockages or build-up at the pick-up, in the water tube or the water channels themself.

You mention this is a "saltwater" version, do you run it in saltwater? If so, you could have significant build-up through out the cooling system which is somewhat restricting the water flow.

You could also have a toasted thermostat(s) - if they are original they may be due for a change..
 
Galamb, if im not mistaken Saltwater is an Optimax.

Bubbco, you need to look at your Thermostats and/or your poppet valve, if the water pump is all good.
 
If this is an Opti an the tell-tale is hot that could indicate a clogged strainer.

The tell-tale on the Opti's are fed by the water channel (hose) that cools the air-compresser.

That channel is split off at the top end of the water tube, and then travels over to the compressor via a water hose (kinda like the heater hose on a car). Where that hose re-enters the block there is a strainer (filter) located with the fitting.

If that's clogged or partially clogged it can lead to an overheat (and alarm) from the compressor which means the heads maybe getting all the water they need (fed by a different water channel not affected by that screen) and are running at "normal" temperature with the thermostats and poppet functioning normally.

Sorry, should have asked in the beginning -

Is this an Opti, EFI 2 stroke, or a 4 stroke???
 
Saltwater series simply means that some components are stainless steel and extra corrosion resistance is incorporated into the motor.

The poppet valve doesn't (kick in) until you hit the low end of mid-throttle - so if all is fine at idle (when the thermostats have control) but you get the alarm (for real - not just a toasted sensor) in/around the 1800-3000 rpm range, that is a good indication the poppet is on it's way out.

The poppet is located under a cover on the starboard side of the block (so on the right side if you are facing the propeller) right at the bottom where the engine bolts onto the leg. It is located right in front of the (bulge) created by the bottom cylinder.

Under the cover you have 11 bits/pieces (gasket, inner covers, a spring, rubber parts etc) so I wouldn't pull the cover without a least a diagram of where everything goes (and a manual would definately be a better choice).

Merc sells a whole kit to replace the poppet which should be done as part of regular maintenace every 4 or 5 years (thermostats should be replaced or at least tested at the same interval)...
 
Thanks so much for your help. I will start replacing parts to try to find the problem. You guys have been very helpful,and I am glad I found this website.
 
Please post what parts replacement fixed your overheating problem...

I'm having the same issue as well and following these threads closely now..

I just installed a new water kit and awating to test it out. The poppet valve is my next suspect if overheatiing continues...

Anybody - How high can you run your engine while hooked up to the muffs and water hose?
 
If you are asking about rpm's, keep it at 1000 or below.

A garden hose just can not supply enough water to keep things cool (the water pump will "starve") above about 1000 rpms.

If you want to "rev it up" you need to (tank) the motor. Most of the higher horsepowers are a little too big for a standard garbage can but you can use a large (rubbermaid) bin - just keep the water level at or above the cavitation plate and keep the hose running to keep the tub filled - that will allow you to sustain mid range rpms for a bit with occasional full throttle bursts.

Just mind the tach if it's not in gear - without turning the prop (which is hard to do except in an actual test tank) your motor can "run away" (over rev) - so keep a close eye on it...
 
Back
Top