1998 3000SCR alarm Temp switch

[jparsons121]

That tube wouldn't affect high RPM cooling.

Low water flow will. Do the flow test to be sure you are pumping the volume per spec. High RPM cooling alarm will usually be due to a worn impeller or a restriction in the inlet flow.

I chased a similar issue and it turned out flow volume was low due to the transom tube being partially blocked due to corrosion around the hose (known issue with Bravo drives).

[mmwjr]

Originally Posted by jparsons121

That tube wouldn't affect high RPM cooling.

Low water flow will. Do the flow test to be sure you are pumping the volume per spec. High RPM cooling alarm will usually be due to a worn impeller or a restriction in the inlet flow.

I chased a similar issue and it turned out flow volume was low due to the transom tube being partially blocked due to corrosion around the hose (known issue with Bravo drives).

He is correct Bravo drives are know for restrictions at the transom hose due to the retainer design.

[case1]

Is this transom hose restriction area accessible with the boat in the water?

[jparsons121]

Yes and no...
Inside at the top of the transom bracket there is a fitting that the intake hose is attached to. You can remove the two screws an somewhat inspect that area..
Warning.. You can get a small stream of water flowing out so be sure to think thru the process and have a plug ready. Order new gaskets prior, as they will probably be shot once removed.

To examine it fully, from both inside and out, will require the boat out of the water.
As Mike mentions, the restriction is due to the hose passing thru the transom bracket and having a retainer that screws into the inside of the hose, expanding it against the hole. So the only true way to inspect is removing the fitting inside, use the special tool to unscrew the retainer and remove the hose from the pass thru hole.

This is why I recommended to do the flow test outlined in the manual to verify a restriction in flow prior to chasing this particular cause.

John

[mmwjr]

Originally Posted by case1

Is this transom hose restriction area accessible with the boat in the water?

The only guaranteed way is to pull the boat remove the drive to inspect the hose. If blocked the hose and retainers need to be replaced however this is also the time to replace the bellows and lower shift cable.

[case1]

Update:
The flow test seamed be to be time consuming and hazardous due to the rotating parts and belt, so being that I had already purchased the impeller I changed it first. The impeller was a bit worn but not too bad, started the engine and warmed up brought up to 3K and alarm went off again. So I proceeded to perform the flow test the instructions call to run the engine at 1000 RPM divert the discharge from the sea water pump to a bucket for 15 seconds and measure the volume should be 8 quarts or 2 gallons. I used my 3 gallon boat wash bucket extended the hose to get a connection away from the roatating parts, started the engine brought up to 1K? (RPM meter I had purchased for this test from Harbor Freight is a POS) switched over from the engine to the bucket and in 15 seconds it overflows the bucket. So although I can't say for sure I was at 1K I think that there is plenty of flow. Keep in mind that the engine doesn't over heat but runs at 175* alarms triggers for a few seconds and shuts off. So I pulled the thermostat and performed the test in the pan of water on the stove it appears to crack off its seat at about 165-170* and open a good amount at 185*. I thinking my next step will be to purchase a new thermostat p/n 8m0109441 160*? Or should I get a 140* stat?

[mmwjr]

Raw salt water should be 140 and raw fresh water is 160. Has to due with the temp at which salt crystals form.

[case1]

Update:
I slip in fresh water but will cruise in salt water.
Replaced both thermostats with 140* stats no more alarms so far but still think something is up with the starboard engine, the temperature gauge hunts between 150-175 whereas the port engine fairly stable about 160*

[mmwjr]

Originally Posted by case1

Update:
I slip in fresh water but will cruise in salt water.
Replaced both thermostats with 140* stats no more alarms so far but still think something is up with the starboard engine, the temperature gauge hunts between 150-175 whereas the port engine fairly stable about 160*

Using an IR temp sensor and taking reading of the eng8ne and exhaust occasionally see if any reading are varying as the gauge is. IMO the helm gauge tend to be off and vary as the boat gets older. I have seen adding a ground wire to the sender body help. Use a big alligator clip to grab the body.