boat running hot 1999 5.0 mercruiser

[junnerbug]

Hi everyone this is my very first post.

I am the owner of a 1999 Searay 19ft C.C. The boat has a 5.0L Mercruiser which is carburated 220HP with an Aplha 1 generation two drive. I just bought the boat this year and it runs excellent except for it is running hotter than it should. The boat is running anywhere between 175 - 190 degrees. I have replaced the thermostat, it has a new impeller, new temperature sending unit, and the gauge has been checked an is ok. The infared shows approx 150 degrees at the thermostat housing and the port riser/manifold is 140-150 and starboard is 180. The olny thing i have noticed is there is not much water coming from the prop barely any, it is all coming from the bypasses while on the muffs. I boat Lake St.CLAIR which is part of the great lakes in Canada. The water temperature is approximately 60 degrees right now.

The impeller was changed by previous owner as he had it blow apart on the water. I have torn it apart again and checked it and replaced it again no change though.

any suggestions would be great I am at a loss of thoughts

 

[HT32BSX115]

Re: boat running hot 1999 5.0 mercruiser

Howdy,


You may have remnants from previous impeller failures in the oil/PS cooler.

That will restrict water flow. Also, corroded manifolds and risers will restrict flow. The water is pumped in by the impeller but must also have an easy path out.


Regards,

Rick

 

[junnerbug]

Re: boat running hot 1999 5.0 mercruiser

Thank you for the reply I forgot to mention I have pulled and flushed the cooler. Also just to mention the boat has only been in fresh water. I also forgot to mention that with the thermostat pulled the boat never got over 100 degrees.

 

[Lupus]

Re: boat running hot 1999 5.0 mercruiser

Hi,

I am sure you will benefit from this forum. It is great! - Welcome on board.

Concerning your problem, - First do not worry about the starboard manifold showing 180 degree, It is still acceptable.

I am quite sure you have a problem with the wiring from the temp. sensor to the gauge. You say that the termostat housing by a temp. gun reads ard. 150 degree. The temp. sensor (new and in order) is located in or around the termostat housing so this is the reading being send to the gauge. If the gauge is measured to be in order there is no other things but the wiring... Not sure but I believe that bad wiring will cause a higher reading on your gauge - Check for corrosion in the wiring and I am sure you find your problem.

 

[Fun Times]

Re: boat running hot 1999 5.0 mercruiser

When you replaced the thermostat gasket did you install it dry or did you put some kind of adhesiv to the gasket? If there is any kind of sensor mounted on the thermostat housing then the sensor is not getting a good groung and the little metel crush rings on the gasket are not braking thru the adhesiv and not letting the sensor ground out to the intake manifold, Or the manifold [and] "Or" the Thermostat housing was not cleaned enough when removed the first time. If the sensor is not grounded the gauge will not read right and normaly read high or a sometimes the gauge will travel from high to varry low when running. If that checks out ok then your gauge it self is most likely off. I say this because you already said it is staying at 150 degrees with the infau red gun and that would be ok, Also read the temp on the intake manifold by the T/housing. What degrees thermostat did you install? By the way most gauges will read about 10-15 degrees higher then what ever temp size thermostat you installed If the temp gauge is truly reading 182 degrees or more all the time that would bug me and I would install a new gauge and try it. If you put a 160 degree thermostat in I would be fine with a normal reading of 175 reading, And with any thing over say 182 on the gauge AND you know for SURE the engine it's self with the "gun" is reading around 160-170 max after a long hard run then it would be time to try running a new wire from the sendor unit on the engine up to the back of the gauge for a quick test and if that dose not fix it then try a new gauge. And if you put a 140 in then just drop these numbers down to 160- 165 on the gauge. Was their a lot of water coming out of the by pass holes? By the way that is also normal and really the only time you would get a lot of water out the prop while on the trailer would be to rev the engine up fast. You should always carry your infa-red gun as a needed tool in the boats tool box if not for you maybe some one eles some day I hope every thing turns out ok for you with this and I hope I helped you in some way with this Good luck with it.

 

[MikDee]

Re: boat running hot 1999 5.0 mercruiser

Thank you for the reply I forgot to mention I have pulled and flushed the cooler. Also just to mention the boat has only been in fresh water. I also forgot to mention that with the thermostat pulled the boat never got over 100 degrees.

What do you mean Cooler? Is this a fresh water closed cooling system?

 

[Backyardhockey]

Re: boat running hot 1999 5.0 mercruiser

If the T -stat is a 160 your fine, should read 175-180. Go boating.

 

[MikDee]

Re: boat running hot 1999 5.0 mercruiser

If the T -stat is a 160 your fine, should read 175-180. Go boating.

The standard raw water Merc. thermostat is 145 degrees

 

[junnerbug]

Re: boat running hot 1999 5.0 mercruiser

Thank you everyone for the replies this is a great forum. Slowly getting to the problem. As a last ditch effort put another new thermostat in and the temp came down to 170 on the gauge. Infra red on the houseing 150-160.

Thank you again