1999 502 Mag Runs at 100* Need some help...
 

I have a 1999 Baja Boss 302 with twin 502's. I just picked the boat up and noticed that it always ran right at 100 degrees. I pulled the T stat housings and noticed there were no thermostats. I know this is causing a rich mixture. The transom is covered in soot!

So... I picked up some Sierra thermostats and put them in. NO CHANGE! Pick up impeller is good, no water is pouring out of the engine anywhere in bilge. Good water out of the exhaust.

I am stumped!

The thermostats were put in the correct way. (I know someone will ask)

Might want to check the temp gauges and sending units to see if they're working. Do you have oil temp gauges?

No on the oil temp. The t stat housing is cold. I have an infrared, just not out here on the lake with me.

I ground the gauges, the peg. Also, when stopped the heat soak will get the gauges up to 110 or so. As soon as it is started they cool right down.

I think I found my problem. I am missing the the little plastic thing that is right under the T stat.

Would that cause my problem?

http://www.marineengine.com/parts/me...MMON/20115.gif

Mr. Gasket Water Outlet Restrictor Plate Kit - JEGS what about something like this? My boat runs 110 degrees and soots the transom also. With my boat having a procharger I'm wondering if I could use one of these also

98/99 502s were very well known for sooting it up :( Mine always have. Best thing that helps cure it is higher octane gas! At least what I have seen on mine anyway
However, I do run the thermo's and the white bridge peice your refering too.
Typically I am right around 165-180 with the obvious changes with colder waters. There are times i am only at 100 due to that.

I would NOT run those restrictors in my opinion! If your stock motors, run stock parts :)

No more black haze, engines run smoother, more fuel economy, about 2 miles per hour on the top end.

The engine is in a cold loop, it is giving it more fuel then required to try to get the temp up.

The t stat does not go on the lip in the manifold, the plastic retainer actually hold it into place in the upper hose housing itself.

I hope there are enough search terms in this thread for someone to chase down this same problem.


Rookie mistake not knowing how they actually work.