110 yanmar overheating

[sabadd2003]

We have a 25 classic Ranger 25 with a overheating issue.
Background of the boat
it has 6- 27 batteries installed on the port side 4 are for the house which two will be removed soon.
Installed a new thermostat, could that have been installed improperly?
A new sea water pump with new impeller. could the factory have put the vanes in the wrong direction?
The reservoir is always at the full mark.
Looks to me like it pumps good water out the exhaust.
The hull and running gear are clean.
While under way
2200 rpm 6.5-7 knots 175 degrees
2400 rpm 7-8 knots 185 degrees
2800 rpm 7-8 knots 190 -195 degrees
3000 rpm 8-8.5 knots 210 degrees and climbing.just for 2-3 minutes
It will drop down to 175 degrees when put at 2200 rpm fairly quickly.
She has never hit ten knots on flat water going wit the flow. Going against a 3 knot current in Admiralty inlet we were doing 3-4 knots in the boat.
Not sure what is causing the overheating , or the lack of speed. Could the propeller be under pitched
and overloading the engine?
Is is the fresh water cooling or the seawater system not working properly?
Any advice will be appreciated.

Thanks Steve
Slo Ranger

 

[knotflying]

It is not uncommon for these engines to get "hot". However in your colder water it should be less common. Remove the end caps off the transmission cooler and make sure they are not plugged up with grass etc. At the same time look at the condition of the cooler vanes. You may need to do a descaling if they look like they have a lot of build up. RoaM & i did an entire thread on flushing the sysTem, if this appears to be the problem.

 

[baz]

First, it does not matter about the impeller vanes being one way or the other. Once the impeller rotates the vanes will bend to their proper position with one or two rotations.

If water is shooting out with the exhaust then the impeller is working AOK.

Is the raw water pumps pulley belt tensioned correctly.... maybe it's slipping if not correctly tensioned.

I would certainly check the thermostat for being the correct one for the Yanmar 110HP engine.

Possible air pockets in the internal cooling. The raw water is used to cool the internal closed cooling system via a heat exchanger.

You can run the engine up through RPM ranges by depressing the button at base of the throttle lever and then moving the throttle lever. If you do this does the engine water temp climb above what's acceptable ?

 

[SGIDAVE]

Hello Steve,

As Barry has said, the impeller is probably fine if you have decent water ejection from the exhaust. If this is a "new" problem which just started after the thermostat was replaced, then scrutinize the new thermostat installation. For instance, ensure it is not 'upside-down.'

You need to trouble shoot the cooling system.

The cooling system may have 'junk,' grass, or even mineral-type ('scale') obstructions. Has the heat exchanger core ever been serviced?

You said the bottom is clean...does that statement include specifically the raw water intake opening? Bottom paint and/or barnacle growth can narrow the openings in the intake grate so ensure it is 'wide open.'

If you have the 110 Yanmar, your boat must be...10+ years old I'm guessing? Therefore, check the INTAKE side of the raw water hoses for collapsing (and thus restricting raw water flow) at higher engine rpm. I'm talking about the hoses from the through-hull to the engine-driven raw water pump; downstream from the pump the raw water circuit is no longer sub-atmospheric (i.e., 'suction').

Let us know what you find,

dave

 

[doke01]

Could be the thermostat is not opening properly. Take it out and boil water to the opening temperature. Drop the thermostat in then pull it out and check to see if it is open.

Could be that you had an air pocket and you actually don't have enough anti-freeze in the system. Let the engine cool and take off the radiator cap, the antifreeze should be to the top. If not, fill it to the top. The overflow reservoir does not indicate how much anti-freeze is in the system.

Other causes, barnacles/foreign material in the heat exchanger (as others have mentioned), barnacle growth on the bottom/prop, partially blocked raw water intake. Dirty raw water intake filter.

It is likely the impeller is good if you are seeing water come out, but there have been cases of faulty impellers where the impeller rubber slips around the hub when going higher speeds. Still, not likely.

Since you appear to be overheating at higher RPMs, it is likely to do with something impeding the raw water flow. However, low levels of anti-freeze can cause the same symptoms and seems more likely since you just had work done on it.

 

[sabadd2003]

Today I flushed out the sea water cooling system from the transmission to the mixing elbow in reverse flow with Barnacle Buster. It ran for 2-3 hours and a lot of gunk came out. Then as I put the hose from the sea strainer to the trans. cooler I noticed there was no flow when I opened the sea cock. l lowered the hose water came gushing out. Maybe it had a air lock or the pump was not able to over come the suction need to get a good flow of water. But flow has improved. Also the anti freeze left on the boat by the previous owner was not a 50-50 mix as recommended dy Yanmar but full concentrate. So we will flush the fresh water system this week I hope that's the cause.
Will let you know.

 

[knotflying]

You should use the long life antifreeze. I usually use the Prestone. If you buy full strength and dilute it, make sure you use distilled water.