1983 Chrysler Sea King 15 hp startup after rebuilding

[turbulence]

I rebuilt this motor which was running on 1 cylinder and now it seems to be ok except I'm curious as to how hot the head should get. There is no water jacket in the head so I suspect it runs hotter than one with water circulating there. I don't want to ruin my rebuilding work by having it overheat right off. The impeller has already been replaced. I've only had the motor running in the tank for about 5 minutes so far and I could only hold my hand in the head for a couple of seconds, is that too hot?

 

[turbulence]

I rebuilt this motor which was running on 1 cylinder and now it seems to be ok except I'm curious as to how hot the head should get. There is no water jacket in the head so I suspect it runs hotter than one with water circulating there. I don't want to ruin my rebuilding work by having it overheat right off. The impeller has already been replaced. I've only had the motor running in the tank for about 5 minutes so far and I could only hold my hand in the head for a couple of seconds, is that too hot?

I ran this motor for 5-10 minutes and checked the head temperature with an infrared thermometer, head temp was 199, the block temp was 140.

 

[alldodge]

No expert but 199*F doesn't sound bad to me for the head

 

[turbulence]

Thanks for your input. I don't have much experience with outboards and don't want to ruin something out of ignorance.

 

[alldodge]

I'm in your same boat with OB
Maybe @jerryjerry05 or other will comment

 

[jerryjerry05]

What did you do for the rebuild? Pull the head?
The 15hp Chrysler and some older Forces didn't have a
thermostat.
So the temps should be lower than the 140d you say the
block is???
First thing? how deep in the bucket is the lower unit when
running?
It needs to be 4" over the cavitation plate or use muffs
taped in place.
Running in a bucket, the water heats up fairly quick and
the motor can get hot.
You said the impeller was changed earlier, You do it?
What condition is the pump housing, wear plate?

 

[turbulence]

on the rebuild I completely disassembled, checked the main bearings, checked the rod bearings, found some scoring in the cylinders and on the pistons. I honed the cylinders and sanded the roughness off the pistons with a fine sandpaper (600 grit). The rings were stuck on the pistons but I was able to remove the residue and the ring end gap was very close. I had to re-use the rings anyway since I couldn't find any. The impeller had recently been replaced by someone else so I checked it and found it in very good condition but the housing was rough with surface corrosion. I was able to remove the corrosion with sandpaper which left some very minor pitting. Everything was carefully re-assembled and a compression test showed 90 psi on both cylinders. The water level in the tank may have been an inch or two lower than your specs but I was getting a good bit of water out of the upper discharge ports. I was using a smaller water tank (about 30 gals) so that may have been a contributing factor.
I didn't really think the head temp should be as low as the block temp since there is no cooling water circulating in the head but I didn't know what to expect. I'm going to change the Lub in the lower unit tomorrow and plan to give it a little test on the lake Sunday.
thanks for the response and the tips. I'll report back after Sunday.

 

[jerryjerry05]

Since you've had the head off, you know where the cooling
passages are. Run it in the lake and check the temp where the
cooling passages are.
Right around the spark plug of course will be the hottest,
but at the cooling passages it should be closer to the temp of
the water.
I've heard if your using the wrong plugs? Running a hotter plug can raise the
temp??(not positive this is true???)

 

[turbulence]

thanks JerrryJerry05

 

[turbulence]

Since you've had the head off, you know where the cooling
passages are. Run it in the lake and check the temp where the
cooling passages are.
Right around the spark plug of course will be the hottest,
but at the cooling passages it should be closer to the temp of
the water.
I've heard if your using the wrong plugs? Running a hotter plug can raise the
temp??(not positive this is true???)

Went out on the lake today. Motor performed well but still needs some minor adjustments. Had no problems with the overheating concern. Oops, after checking it turns out that the tank I was running it in was only a 10 gal tank. I won't make that mistake again.

 

[jerryjerry05]

A 10gal tank compared to a gazillion gallon lake???