So after reading last week's topic about impellers and temp., etc., I got curious about my temps. A couple weeks ago I had an odd smell at higher RPM, or actually when slowing down from high RPM .. Not sure what, but something was cooking that smelled bad.. Maybe burning rubber-ish, but I'm from Akron and I know what burning rubber smells like.. And this was similar... So today in he later afternoon after a 45 minute or so cruise on a deceivingly calm looking Lake Erie (wind was pretty funky, swirling and catching the boat making it do some odd pitching ) I decided to check. I got out my laser temp gun (Excellent Tool box addition Jeff, do I get a gold star? Got mine two months ago at Harbor Freight for @ 25 bucks..) and checked the exhaust manifolds about 5 minutes after we docked. The stbd engine stbd ex. manifold was 141 and the other three were @ 115-119.. Impeller on stbd engine changed last year by Pier 53 marina per previous owner's request. I have the receipt. Previous owner said it wasn't pumping H20 and called them. They replaced impeller. Everything seems to be running well, but the reading was a skew enough to make me wonder. Temp gauges while cruising are at @ 145-150 both engines.. Have similar amounts of H20 and steam from both exhausts while cruising .. Usually around 2500- 3000 RPM. Also I am installing MSD blaster coils that I went to Summit Racing and bought last Friday. There are Blue Streak coils on there now.. Think the stbd coil is cheesed up a bit. Engine sounds weird at higher RPM ... Should I change the stbd impeller myself and clean the crap out of where it seats or not be concerned? Anyone?... Buehler?
Thanks!
Sean

Used to use stickers that record the highest temperature reached by changing color. Might be useful to catch heating problems in the exhaust manifolds that would otherwise go unnoticed. I know that Scigiene in Canada makes them for medical purposes ( http://www.scigiene.com/...pment_sales.php?catId=6 ) but they can be purchased here too....

The advantage is that you can see if there was an overheat condition during the last run by checking the sticker when the engine is cold, during your pre-start once-over.

So.. Should I leave it or tear it apart? Can I check for an obstruction without pulling it apart? The other three manifold temps are the same ( both stbd manifolds and stbd side port manifold) so I don't think that water is diverting from that one to the stbd side of the port engine..
Thanks Sean

Hey Karl, I don't have those modules on my 318's.. I have the voltage regulator and the other parts mounted on a steel panel above the trans... I guess it's before the ignition module era.. What effect would that have with exhaust manifold temps? Oh maybe you mean the smell.. Yeah, I don't think that's it..
Thanks!
Sean

So the manual says there is an exhaust manifold thermostat in there. I don't have time to elaborate, but anyone familiar with this? Shows it as a intake type thermostat mounted vertically in the manifold.
Sean

Hey Jeff, M273 and LM318 engines..

The manual states that " All fresh water cooled engines have had incorporated within the exhaust manifold (or upper portion of "S" type riser if so equipped), a thermostat to control the exhaust manifold temperature. " Then it shows the diagram. The thermostat is part # 2847431

Also regarding engine overheating or exhaust manifold overheating ( M273 & LM318 with single 1'' water inlet)
"When engine overheating is encountered, or a condition where exhaust manifold overheating fluctuates from side to side, a restrictor installed between the exhaust manifold and the exhaust elbow ( or between "S" riser and exhaust manifold where risers are are used) will stabilize the cooling system. "
It is essentially a washer .94-1.10 in diameter with a .35 hole in the center and is .30-.35 thick. These are the exact dimensions in the manual.

It continues: Restrictor is to be assembled into the machined recess around the water outlet passage in the exhaust elbow.
In emergency the flanged end cover from exhaust manifold thermostat P/N 2847431 may be used as a restrictor.
In cases where an old style exhaust elbow without the machined recess is used an additional gasket, P/N 2847432,
assembled between exhaust manifold and exhaust elbow should be used to locate the restrictor in the correct
position.."
Signed J.J. Bartos

Ah-hah! So that's where they may have stuck the little darling. Never seen one, but that means nothing. I have to rip my starboard elbow/ riser apart tomorrow morning, so I'll see if there's a spot in the castings where it would go.

Jeff

PS: All in all, I'd toss that sucker out if it's there--it could cause may too much deviltry.

Will do. The water has to go somewhere, so I don't understand why anyone would try to restrict it like that.

Jeff

Correct me if I'm wrong (hah!) but isn't your motor fresh water cooled? No raw water is flowing through it, right?

Jeff

Raw water cooled.

I pulled the elbow/ riser apart this morning and, yes, there is a place where a t-stat could go. But, it would need to be machined for it, and it is not.

Jeff