Gso 480 operating temp

[12ftgso480]

So I've done my fair share of reading through manual and on the forums I'm trying to figure out what an average operating temp for my gso 480 is. a couple guys made it sound like 190-200 ish was getting a little warm but my manual says maximum of 235 oil temp can anyone help clear this up for me definitely don't want to burn it down thanks in advance. I think we have a 2 1/2 gal oil resivoir, no baffles in it and a stainless heat shroud on top. Ive seen it get up to 190. Thanks in advance.

 

[Dirtman]

I'm sure that someone with more experience with these motors will chime in but I don't think that 190 on oil temp is too bad it's my understanding with these motors that cylinder head temp is the killer of these motors. I'm just starting to run a GSO540 myself so I will be watching for more informed opinions.

 

[Slidin Gator]

180 is when the thermostat opens, 190-200 is perfect, trust the manual, they wrote it in 1950 and haven't had to change it. Dirt man is right, cylinder head temps are what you need to watch, particularly on a GSO.

 

[SuprchgedPalmBeach]

Use the right shroud for the prop your running & give it plenty of fuel. I can hunt dry all day...well 3 hrs. or so till I burn 40 gallons, and never reach 190 degrees. I run (2) Carter 4600HP Fuel Pumps to each side of a Holley AED 850, 1/2 fuel lines & Racor S3232 Filter.

 

[12ftgso480]

So with the watching the head temp do you guys have a temp guage on the heads some how to watch while running? Only temp guage I have right now is on my oil. This is my first boat and have only had it out 6 or 7 times. Typically only turning 2000 to 2400 rpm mostly on the water. Thanks for all the info. Much appreciated.

 

[kwanjangnihm]

So with the watching the head temp do you guys have a temp guage on the heads some how to watch while running? Only temp guage I have right now is on my oil. This is my first boat and have only had it out 6 or 7 times. Typically only turning 2000 to 2400 rpm mostly on the water. Thanks for all the info. Much appreciated.

Here is some great info from slidin gator on cylinder head temps and gauges!

Figured I'd rope this conversation back to Rick's build thread.

Yep, didn't notice the shrouds until now Jeff. Never had one, but I hear they keep them cylinders cooler...especially the middle ones. You run a shroud on your aircraft engine?
Rick

Rick I plan to have a larger shroud built for my AV540 once I get it back together. I am going from carb to fuel injection so hopefully this will help with cylinder head temps like slidin gator has referenced in his threads.

After instrumenting all 6 cylinders on a carbureted engine without a shroud, we found that the middle cylinders run hot, real hot and the outer cylinders run much cooler, sometimes too cool. Adding a shroud really brought down the middle cylinders and helps warm up and stabilize the outer cylinders in the more optimum range. Shroud height is a trade off, you want to find what works for your setup without going too much and impacting performance. The original short shroud was not enough for our needs, add an inch and all cylinders are running between 250-350 continuous hard load, right were we want them.

My suggestion is to start with no shroud and instrument the engine with CHT's to find out what your setup needs. I recently added CHT's on cylinders 3 & 4 on my injected engine. I find #4 at 325-350 and #3 at 200, I am not running a shroud. I have not yet moved them around to see what the other cylinders are reading. I have run with a few injected Continental 520's with CHT's and they see similar results without a shroud.

Here is a 2 cylinder CHT parts list:

2x CHT Probes, $43 each
https://www.aircraftspruce.com/catalog/inpages/grandrapidchtbay01.php

2x CHT Probe Adaptor, $6.50 each
https://www.aircraftspruce.com/catalog/inpages/grandrapidchtadp01.php

1x Westach Dual CHT gauge, 2DC8, $121.50
https://www.westach.com/product-page/2dc8

1x Gauge light kit, #186, $5.80
https://www.westach.com/product-page/186-1

So about $250 total with shipping and tax. You can get cheaper CHT sensors, but they are the spark plug gasket type, which eventually wear out like all spark plug gaskets and I have found up to 50 F lower reading with my thermal gun at the spark plugs vs. the bayonet CHT' readings. The adapters screw into ports under the bottom spark plug, the sensor is a spring loaded, bayonet fit into the adapter, it puts the probe at the base of the cooling fins. The gauge comes with a short whip, I soldered the leads to some #22, dual twisted pair wire to extend to the sensor leads. If it does not read anything, reverse the wires.

 

[Slidin Gator]

The oil temp gauge is an excellent way to measure oil temp, but pretty useless for measuring cylinder temps. Water cooled CM engines monitor water temperature, kinda hard to measure air temperature where it matters. Aviation engines are air cooled, not oil cooled, one needs to monitor cylinder temps to know what the deal is.

I have seen 600 F on the cylinder gauge before the oil got warmed up. On the other hand I have had to deal with keeping the oil temp below 235 F with a hole in one cylinder while all the other cylinders are running in spec on temp. Cylinder temps can range 200 F difference between cylinders!

The manual gives the operator an operating range, as long as the oil temp is between 180 and 235 F, you have not hurt the oil or the crank/cam etc. These are the operating limits, I could tape up my cooler NASCAR style and keep the oil at 210 F running dry all day and feel just fine about it, as long as cylinder temps are good. I see 150-200 F difference between cylinders normally, so what does +/- 20 F in oil temp tell you for cylinder temp?

My point, the oil temp gauge tells you what the oil temp is, period. CHT's tell you what cylinder temps are. You need to know the status of all of this to keep the engine operating within specification.

 

[12ftgso480]

Thank you all for the fast response. This has all been a great deal of help and has me headed in the right direction. Upon purchase of this boat we were told one of the middle cylinders had been replaced and it came with a spare cylinder as well. After the cylinder replacement they installed the shroud, it seems alot taller than most I have seen with no holes in the top. I'll have to check out these links and will feel alot better about operation getting a temp guage on the heads. Thanks again.

 

[12ftgso480]

Also are we wanting a 250 to 350 reading ? At what point would we want to shut down ?

 

[Slidin Gator]

12ft,
That all sounds typical, #4 cylinder (middle Stbd side) got too hot and dropped an exhaust valve seat, with the shroud you are probably ahead of the game, but obviously some CHT sensors would be good. Lycoming specifies 400 F or less CHT (cylinder) temp for maximum life and 500 F max with reduced life. At 600 F you can expect to replace the cylinder very soon. Cold cylinders are wasting fuel.

Those GSO setups normally throw a big prop and need a taller shroud than you will see on my post, which is what you seem to describe. The higher they are in the rear, the more suction/airflow and therefore more cooling. Post some pictures, but it sounds like you are set up properly.

Per the manual, shutdown if oil temp exceeds 235 F, so get whatever oil temp gauge you want that reads higher.

 

[12ftgso480]

Here is one of the better pics I have if it on my phone I can measure if anything looks iffy to you from the pic?

 

[SuprchgedPalmBeach]

https://southernairboat.com/phpBB3/download/file.php?mode=view&id=21296

 

[nunook]

Mine will run 190-230 depending on how hard it is ran with a shroud, I read thru one of the lycoming articles and it suggests to run around 220 to burn off any moisture (condensation) which may have formed in the oil