another 85hp suzi ???

trackersocha

Petty Officer 2nd Class
Joined
Feb 19, 2005
Messages
192
85 hp 86 yr, will a t-stat absence cause overheat?<br /><br />i have an overheat buzzer going off at high rpm for 5-6 min of run time. i have no t-stat, that is the only thing i can think of that would cause this problem <br /><br />help <br /><br />thanks in advance!!<br />love mike
 

jafa

Petty Officer 2nd Class
Joined
Mar 10, 2004
Messages
172
Re: another 85hp suzi ???

Possibly , if the lowest point of the thermostat is below the temp sensor , ie the sensor is above the thermostat, then cooling water empties out before cooling the sensor(and probably the top of the top cylinder).
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: another 85hp suzi ???

Other than the obvious worn things like a worn water pump, high rpm overheats are usually due to a leaking head gasket or an engine that is overpropped and not reaching operating rpm (~5600-5800 rpm). If the engine prop combo and rpm was previously OK, I would suspect the head gasket. Removing the thermostat, while not recommended, won't in and of itself cause a high rpm overheat on that particular engine.
 

trackersocha

Petty Officer 2nd Class
Joined
Feb 19, 2005
Messages
192
Re: another 85hp suzi ???

ok, head gasket, is there any way to check that w/o taking the head off(blead down, etc...)
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: another 85hp suzi ???

I guess a leak down test might pinpoint it. It is also possible that the heat sensor is overly sensitive. You may want to confirm that the engine is actually overheating. An infrared point and shoot thermometer from Radio Shack (~$50) is a useful tool. If the head gasket on that year engine has never been replaced, the replacement gaskets have been redesigned with a larger coolant drain hole to prevent salting up of the coolant passage in the head gasket. Normally replacing the head gasket is a simple and straight forward task but if that engine has ever seen salt water you are likely to break 1 or more head bolts and will need to install helicoil inserts once you get the busted shaft out. (If you go that route do a search on these forums for broken bolt repair and you will receive good info).<br /><br />If you get the head off, check the head for warpage and have it decked flat if necessary and install a new head gasket and torque the head bolts to spec.
 

trackersocha

Petty Officer 2nd Class
Joined
Feb 19, 2005
Messages
192
Re: another 85hp suzi ???

thanks, good ideas, and yes it has seen salt. i have a infrared thermo, and was wondering what temp is overheat?
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: another 85hp suzi ???

Aim the thermometer at the flat area on top of the cylinders just aft of the flywheel but before the cylinder head. It should be 163F or less at WOT. The cylinder heads will run hotter, I think (memory is fuzzy) that the sensor goes off at a head temp about 230 and won't shut up until the temp gets below about 210, so max head temp should probably be about 210 or less (preferably less). Mine, once I got it sorted out, used to run about 190 in the summer.
 
Top