4.3 Gl over heat

[selmahotrod]

My 2008 4.3gl will over heat at 3000 rpm but runs fine normal at 3500 rpm and up. Cool at idle too. What's happening?

 

[Scott Danforth]

when was the last time you replaced the impeller?

 

[selmahotrod]

I just bought the boat, so I have no idea how long its been in there.

 

[alldodge]

I just bought the boat, so I have no idea how long its been in there.

First thing you should do with a new to you boat is;

Change the motor oil
Change Fuel filter

Remove drive, inspect gimbal bearing, U joints and bellows
Change the drive lube
Change the impeller
Check drive alignment

Check the Battery and all connections
Check belts

This way you now have a baseline to determine when things need to be inspected and/or change again

 

[Scott Danforth]

Above is very good advice

 

[selmahotrod]

Dealer said they did alot of that but who knows.

 

[Donald0039]

The raw water impeller is not very expensive. At least pull the impeller and look it over feeling how rubbery and flexible the impeller vanes are. Carry a spare impeller and fuel filter.

Now one potential is broken off impeller vane that is flowed to and is stuck somewhere in the engine.

FWC or RWC engine.

Replace thermostat.

What is overheating, the engine block or exhaust manifold or exhaust elbow/riser?

 

[selmahotrod]

I get alarm, not sure if from engine or exhaust. Gauge shows over 200 when alarm goes off. I put new thrmostat and impella and spark plugs in it. Has been used in salt water.

 

[Lou C]

Next is your exhaust manifolds & elbows. I bet they are corroded inside and restricting water flow.
Time to pull them & inspect. Here's what new looks like for the manifold:

 

[tpenfield]

Cooling issues seem to be one of the most frequent problems with boat engines, particularly sterndrives (I/O). Since the boat is new-2-you, you should go through the cooling system, which it sounds like you have done some.

If the new impeller did not fix the issue, then the overheating may be due to a clog in the water flow. How did the old impeller look? 100% intact?

Marine life and even bits from a failed impeller can clog the water flow before it gets to the engine or exhaust. Back-flushing and checking the various oil coolers along the water flow can remedy clogs.

Also, as mentioned, the exhaust system and thermostat housing can become clogged with rust scale, particularly when used in salt water. The cooling water exits the engine through the exhaust manifolds and/or risers (depending on which cooling system you have). If those things are clogged, not enough 'hot' water cannot exit the engine, so not enough 'cool' water from the ocean can enter.

I've run all 3 of my powerboats over the past 20 years in salt water and all of them had cooling issues at one point or another.

 

[Lou C]

Average life of a cast iron exhaust system in salt water is 5-7 years. This depends on salinity of the water & how often you flush the system.

 

[Lou C]

And keep in mind how different marine cooling systems are compared to auto cooling systems….an auto system is closed and runs on antifreeze with corrosion inhibitors…it can run without maintenance with long life coolants (do check for leaks & worn belts) for many years
Marine systems if open or raw water cooled depend on regular maintenance:
Raw water impeller every 3 seasons or sooner if run in shallow sandy water
Thermostats if run in salt water same thing
Exhaust system 5-7 years in salt water
Note that fresh water is not 100% corrosion free; it depends on the level of dissolved minerals. Any sign of leakage around the joint between the manifold & elbow should be investigated because it could be leaking inside…right into a cylinder….
If you have a heat exchanger you still have the rubber impeller to change & the raw water side if the system needs maintenance (cleaning) as well. Exhaust; if full closed the manifolds last as long as the engine but the elbows are still raw water cooled.
Raw water cooling is not pressurized and depends on a large volume of cool water IN and warm water OUT….

 

[selmahotrod]

sea water inlet fitting Volvo SX-A# 23238467 is broken. Can it be replaced without pulling the drive. I see a special tool 3849648 for the job.​

 

[Lou C]

The Volvo SX-A is a different design than the OMC Cobra & Volvo SX both of which have a similar design. Post the question up in the Volvo section.

 

[Donald0039]

Is it FWC or RWC? You need a Diacom to tell you why the alarm sounded.

 

[Donald0039]

An IR thermometer gun you can point at various engine and cooling system parts is a good idea for $30 or so..

 

[selmahotrod]

sea water inlet fitting Volvo SX-A# 23238467 is broken. Can it be replaced without pulling the drive. I see a special tool 3849648 for the job.​

 

[alldodge]

sea water inlet fitting Volvo SX-A# 23238467 is broken. Can it be replaced without pulling the drive. I see a special tool 3849648 for the job.​

Hey @Scott Danforth

 

[Scott Danforth]

Should just thread in on the SX