Mercruiser 165 overheating? Blower?

[auscarter12]

I have an early 70s model Mercruiser 165 inline 6 sterndrive on my boat. Intermittently, I have trouble keeping the motor cooled down. I recently had a brand new impeller installed in the outdrive so I know that is not the problem - it pumps water perfectly. It is a water cooled system (no antifreeze involved). I also have the correct prop for the motor, so I know it isn't caused by the prop putting too much pressure on the motor. When it does begin to run hot, I simply stop the boat and wait about 3 or 4 minutes and it cools down.

My question is: Does anyone have experience with installing a ventilation blower to not only remove unwanted fumes from the engine bay but to help cool the engine as well? The boat has inlet and outlet ventilation holes which routes cool air into the engine bay while the boat is moving. I could install the blower to blow warm air out of the engine bay, or to suck cool air into the engine bay. I know this is not primarily what blowers are designed to do, but does anyone have any experience with this or know of another remedy to help keep my engine cool?

The only other option I can think of would be to cut holes into the fiber glass engine cover much like the holes in the grill of a Jeep in order to create more airflow.

 

[Bt Doctur]

when was the manifold/riser replaced last?

 

[auscarter12]

Bt Doctur Honestly I have no idea. I just recently purchased the boat. The riser/manifold does not leak. What could be the issue with those?

 

[Bt Doctur]

after 3-6 years they plug up from scale and need replacing. water in=water out to keep from overheatung

 

[oldsub86]

Thermostat??

 

[stonyloam]

As to your original question, no a blower is not going to help. You have a water flow problem. The water passage where the cooling water exits the engine and dumps into the exhaust can become restricted by rust scale like the Dr says. Even though your impeller is working fine you are just not pushing enough water through the engine because of the restricted outlet.

 

[wahlejim]

Your cooling system has many more parts than just the impeller. Look at the manual for your engine in the sticky section. Sounds like you have some blockage somewhere in the system. You cannot use air as a substitute for your cooling system.

 

[auscarter12]

stonyloam BT Doctur Is there a way to clean the elbow and manifold out and clear the blockage instead of replacing them? They are quite expensive.

 

[kmarine]

I recommend getting a infared heat thermometer after replacing the thermostat to see what part of your engine heats up first. Do you have an old piece of impeller stuck somewhere restricting the flow. You might need to flush out the manifold after removing it but look for easier more common obstructions first. Start at the water inlet and work your way to the exhaust.most of the time I remove the thermostat when troubleshooting to circulate more fluid.

 

[auscarter12]

kmarine I removed the exhaust manifold and elbow today. I was going to use an acid bath to flush them but after doing more research that seems to be a very risky situation, so I simply sprayed them with water with a hose nozzle and bathed them in a bucket of water to loosen any deposits that I could not get out with the hose. They were not as dirty as I thought they would be. I'm sure they were replaced at one point, but not sure when. The elbow/riser was much dirtier than the manifold. Because the season is coming to a close, I will wait until next season to replace both the manifold and elbow. I have a new gasket set coming in the morning so I'll put it back together. I also acquired an IFR thermometer so I will test and update with results. Thanks.

 

[Alumarine]

With an I/O you should currently have a bilge blower that is used before starting and while idling.
It is not for cooling purposes but to remove gas fumes in case there's a leak somewhere.

You do have a bilge blower right?

 

[auscarter12]

marc c The boat does not have a bilge blower. It is a 1971 model boat and I don't think the legislation for required bilge blowers came out until the early-mid 1980s. I know I need to install one, I'm just having trouble figuring out where to mount the pump and the hose.

 

[auscarter12]

Can I wire the bilge blower into the same switch as my bilge pump? So that when I turn the bilge pump on the blower comes on as well? My dashboard is lacking room for another switch to be installed.

 

[smokeonthewater]

Put the switch under the dash if needed but no it should be on it's own switch.

 

[FreeBeeTony]

Do you boat in salt water?
If so the manifold and riser are definitely suspect.

 

[auscarter12]

Installed the blower yesterday. Didn't realize how much power those small blower fans had! I put the motor back together and ran it today and noticed that it was running rough. So after checking spark plugs and wires, re-gapping the plugs, using some seafoam and carb cleaner, I realized that the bolt holding the distributor to the block was loose and the timing was off. Readjusted the timing and everything went well - all gaskets have held so far with no water leaks. I'll be taking the boat out to the lake tomorrow so keep your fingers cross for no problems!

I do not boat in salt water. Although, the boat came to be used, so I am not 100% certain where the boat was. But seeing as how I am located in Tennessee, I doubt it has ever been in the salt, thankfully.