Overheating with 5.7 Gxi and DP Drive after Coming off Plane

[Pmcelhin]

Hello,

I'm brand new to the forum. I have a 2003 Four Winns Vista 298 with twin 5.7Gxi (320 hp) engines and DP drives.
Less than 100 hours on engines, raw water cooling, and well maintained.

When you start the engines - both engines gradually increase temps to 175 and hold just fine - which is normal operating temp. I can run the boat at idle or low speed forever and the temps are just fine. Then I put the boat on plane and temps stay at 175 - can run forever with no increase in temps.

Then when coming off a plane and running at slow/idle speed, the starboard engine temp begins to rise and then the overheat alarm sounds and I have to shutdown the engine. I can restart after it cools in few minutes, and the engine is still above 175, and put boat back on plane and the temp begins to drop back down to 175.

So, my problem is only after coming off plane and running low speed.

The impellers were replaced last month during annual service and the circulation pump was replaced as there was some water coming out of the weep hole. And last week, the thermostat was replaced. Also, both drives were serviced and bellows replaced during the service work last month.

I'm at a loss and very frustrated - and my dealer is stumped as well.

Any ideas and information would be greatly appreciated.

Thanks,

Pat

 

[The Revenge]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

I'm real curious to hear how this goes for you. I struggled with the same issue for a year. Nobody could figure it out. My boat did the exact same thing to a T. I have 5.7 Osi's with Xdp drives, 2006's.
I replaced impellers, raw water pumps, had out drives removed and gone through, thermostats, temp gauges, risers removed and inspected, numerous new cooling system hoses. Bought a temp gun to verify temps in the middle of all this.
Not any one thing fixed the issue. But it stopped. Now engines warm up normally and slowly to 175, on plane stay at 175, come off plane and both engines heat up to around 185-190 and stay there for 5-10 minutes if still at idle, if you get right back on plane the temps drop to 175 right away. I'm told this is normal, not sure. I don't understand why the engines never went over 175 for the first 4 years I owned it since new, then they wake up one day and the temps do strange things. No mechanics have been able to explain it either. Please keep me posted. Thanks

 

[kylejb2663]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

Not sure if this helps or even if it's related... Do you trim the drives back down 100% before coming off plane? Maybe some how the wake from coming off plane is causing air gaps where the inlets are... Not exactly sure just a shot in the dark LOL...

 

[Pmcelhin]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

Not sure if this helps or even if it's related... Do you trim the drives back down 100% before coming off plane? Maybe some how the wake from coming off plane is causing air gaps where the inlets are... Not exactly sure just a shot in the dark LOL...

Thanks for your response ...

Yes, I always trim the drives back down just prior to slowly pulling the throttles back. Also, the port engine temp does not (never) increase - only the starboard engine. But I'm at the point that I think there may be an air leak somewhere and air is getting into the cooling system.

Thanks.

 

[Pmcelhin]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

I'm real curious to hear how this goes for you. I struggled with the same issue for a year. Nobody could figure it out. My boat did the exact same thing to a T. I have 5.7 Osi's with Xdp drives, 2006's.
I replaced impellers, raw water pumps, had out drives removed and gone through, thermostats, temp gauges, risers removed and inspected, numerous new cooling system hoses. Bought a temp gun to verify temps in the middle of all this.
Not any one thing fixed the issue. But it stopped. Now engines warm up normally and slowly to 175, on plane stay at 175, come off plane and both engines heat up to around 185-190 and stay there for 5-10 minutes if still at idle, if you get right back on plane the temps drop to 175 right away. I'm told this is normal, not sure. I don't understand why the engines never went over 175 for the first 4 years I owned it since new, then they wake up one day and the temps do strange things. No mechanics have been able to explain it either. Please keep me posted. Thanks

My situation only happens with my starboard engine - the port engine temp stays rock solid after coming off plane.

 

[Pmcelhin]

5.7 Engine Overheating after Coming off Plane

5.7 Engine Overheating after Coming off Plane

Hello,

I realize this a Mercruiser forum area - but thought someone may have had a similar experience with their Merc engine.


I have a 2003 Four Winns Vista 298 with twin 5.7Gxi (320 hp) engines and DP drives.
Less than 100 hours on engines, raw water cooling, and well maintained.

When you start the engines - both engines gradually increase temps to 175 and hold just fine - which is normal operating temp. I can run the boat at idle or low speed forever and the temps are just fine. Then I put the boat on plane and temps stay at 175 - can run forever with no increase in temps.

Then when coming off a plane and running at slow/idle speed, the starboard engine temp begins to rise and then the overheat alarm sounds and I have to shutdown the engine. I can restart after it cools in few minutes, and the engine is still above 175, and put boat back on plane and the temp begins to drop back down to 175.

So, my problem is only after coming off plane and running low speed.

The impellers were replaced last month during annual service and the circulation pump was replaced as there was some water coming out of the weep hole. And last week, the thermostat was replaced. Also, both drives were serviced and bellows replaced during the service work last month.

I'm at a loss and very frustrated - and my dealer is stumped as well.

Any ideas and/or information would be greatly appreciated.

Thanks,

PM

 

[The Revenge]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

My situation started with the port engine only. Then migrated to the other engine too. I'd like to follow along and see if you can find the issue.

 

[Pmcelhin]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

Just hope someone can help me (us) ....

 

[The Revenge]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

Where are you located?

 

[HT32BSX115]

Re: 5.7 Engine Overheating after Coming off Plane

Re: 5.7 Engine Overheating after Coming off Plane

Howdy,


If I was working that problem, the first thing I would do is swap the temp gages (wiring) and and alarm wire to see it it's an indication problem. (or use an infrared temp indicator to check actual temps)

I would also check the impellers again and see if the raw water circuit (oil/pwr st coolers) is/are plugged with impeller fragments (from a previous failure) or other debris.

The "dealer" should be all over this stuff!

Regards,


Rick

 

[Pmcelhin]

Re: Overheating with 5.7 Gxi and DP Drive after Coming off Plane

Dallas, Tx area - Lake Lewisville

 

[Pmcelhin]

Re: 5.7 Engine Overheating after Coming off Plane

Re: 5.7 Engine Overheating after Coming off Plane

Howdy,


If I was working that problem, the first thing I would do is swap the temp gages (wiring) and and alarm wire to see it it's an indication problem. (or use an infrared temp indicator to check actual temps)

I would also check the impellers again and see if the raw water circuit (oil/pwr st coolers) is/are plugged with impeller fragments (from a previous failure) or other debris.

The "dealer" should be all over this stuff!

Regards,


Rick

I stopped by the boat today and checked the temps with an IR thermometer gun I bought yesterday. I didn't have time to take the boat out and run at higher speeds and then back to idle speed. But I did rev the engines up to approx 2500 rpm in neutral for a few minutes. Both engine temps were similar - around 165 degs at thermostat housings and oil filter/assembly. The dash gauges both showed around 170. The exhaust manifolds and risers were much cooler - around 120 degs on both engines.

I then brought both engines back to idle and the temps held - no overheating.

So much for that.

Where is the temp sensor and wiring for the overheating alarm?