Engine heating up...

[Kodiak536]

Few months ago, I noticed that the engine start to over heat while running in my drive way with muffs.

When I rev up the motor, temperature drops to @ normal.

Thinking it may be thermostat, I removed it to find it rusted and stuck. So, I removed and reassembled the housing.

Ran engine and found that it's till over heating without thermostat.

Thinking pump impeller must be the issue so, I removed the lower and found impeller falling apart, just by sitting in my drive way all winter?

Luckily, I had a new kit so, I replaced it as a kit. Still having same issue but, not as bad...that's still with no thermostat installed.

All this happened one week, when previous week it ran fine with no heating problem. Been doing this since then.

I actually replaced the water pump, since it looked rusty and who knows how old it was. Same issue.

Just ran it yesterday and ran salt-off to "flush" the engine, same issue.

Each time when it start to over heat, I rev up the engine and temperature drops, dramatically from @180+ down to below 120.

I can't believe my bran new impeller to be bad. Haven't been on the water yet this year because of this issue.

Why would engine start to over heat and temperature drop when I rev up the engine @1300RPM or more, then repeat this over and over?

[Technical Support]

Hello,

It is possible the flow of water from your hose isn't sufficient enough. Try putting it in the water to see if it gets better. If your boat sits for long periods of time, this can have an effect on rubber parts, especially in the winter. If your boat sits outside during the winter months, it is a good idea to replace the impeller when your boating season starts back up. The temperature dropping when you rev the motor up is because the water pump is spinning faster and pumping a larger volume of water to the engine.

[Kodiak536]

Thanks for info.
As mentioned previously, the impeller had bern replaced, it was falling apart but, all pieces were accounted for.
As for rubber hoses, it does look as though supply hose, @1" diameter from lower unit, seem to be kinked slightly when drive is lowered full down.

Yesterday, I ran the boat again, after one round of salt-off flush the day prior, temperature problem improved but, still climb above 175 on gauge until revved-up and drop down to @supply water temperature from city water.
I used the laser thermometer to check the thermostat housing as engine ran, indicated temperature were @180 on gauge, thermometer showed at most @160, which is still high for running without thermostat.
I will replace the supply rubber hose next to see if that "kink" may be the cause as you suggest as restriction of flow...makes a lot of sense to me.
I'll report back with result when done and tested.

[Kodiak536]

Finally, I got the replacement hose, bit too late for this season's fishing plans.

My next question is, do I need to completely remove the drive just to replace the hose?

Seems kind of tedious considering it's just one hose with 2 screw clamps holding it in place.

[Technical Support]

There is no need to remove the drive to replace that hose. It is connected to the transom assembly on the inside of the boat, then it connects to your water pump on the motor.

[Technical Support]

Let me walk back on the last post. If the hose you are replacing is on the bellhousing and it connects to the transom, then yes, you will need to take the complete drive off to replace that hose. This is the only way to replace that hose. Sorry for the confusion.

[Kodiak536]

As thought as such, were hoping I missed something in all the videos I watched for out drives. Thanks.