• If you log in, the ads disappear in the forum and gallery. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

High CHT on a GPU

TSnake

Well-known member
Hey All-

First, let me thank everyone on this list for all the knowledge I’ve gotten here. I’ve got my first boat last year, and the information I’ve gotten from this list has been incredible.

Ok, on to business. I just put on a new (fresh from generator) GPU to replace a worn out one. I installed a CHT gage while I was at it with the thermocouple installed on the left middle cylinder. I took it out for its first shakedown run this morning. Calm day, temperature in the low 60s. Great morning for a ride. The new motor ran great! However, the CHT gage came up to almost 500 degrees with easy running, and hit 550 when pushing it fairly hard. Oil temperature barely registered on the gage. Seems way too hot, especially on a cool morning with just my skinny butt in the seat. What do the rest of the GPU folks do to keep cool? Does anyone make a good shroud for this engine, or anyone have tips for building one?

Thanks for the help.
 
I had problems with high temp. I finally put some lucas gasoline treatment in could not believe how good it worked. :shock: It lubricates the valves so they don't create as much heat.
 
Mug timing huh? I had not thought of that. Should I try retarding the timing to reduce the head temp?
 
What kind of fuel are you runninng, avgas or car gas? Avgas is designed to run cooler for an aircooled motor. Running car gas tends to drive the cylinder head temps up.
 
I confess. I have been running pump gas. Since this is a stock GPU with stock low compression, I didn't think I needed to use avgas.
 
You don't need to retard the timing. Just make sure the timing is correct. 20 degrees before top dead center is all right. Avgas is the thing for all air-cooled engines. You can run mogas but just make sure when you do that you do not run it hard enough to over temp the cylinders. As long as you keep your cylinders below 450, you should be fine.
 
Does anybody make a 4 in one CHT for a 2" hole?

or a dash mount that has its own little panel?

Scotty
 
I usually run about 28 degrees for a single mag and about 26 degrees on a dual mag enging. You can get a gauge for a 2" hole that reads all cylinders.
 
Search http://www.aircraftspruce.com for "CHT Gauge". I saw several dual gauges and several single gauges that were selectable between 4 or 6 cylinders in their catalog. I've got a single 2" Westach gauge, with the thermocouple installed on the left middle cylinder. I was told that was the cylinder that gets the least airflow. It would be nice to know if the other cylinders were running as hot as that one is.
 
Back
Top