TOPIC: '96 Rude thermostat

My young neighbor bought a nice fishing boat with a '96 90hp Evenrude. He had a dealer replace the carbs because the dealer said one was cracked(???) The motor runs great when it warms up but stumbles when it's cold. After it warms up it starts and runs great even after a shutdown and a restart. He thinks it has something to do with the idle adjustments, to me it sounds like a thermostat issue that's maybe stuck open maybe gunked up after all these years. The neighbor says it spits water out the holes good and does not overheat. Any opins?, where is the temp control located?
Thanks.
Cal

My experience with the OMC V4's is mostly on the older models Cal, early to late 70's. Maybe some of it might be of assistance though. I've noticed they are cold natured beasts, like to be warmed up a little before taking off. (A general statement, but I let mine idle for 5 or 6 minutes before ever trying to move the boat!)

Not sure about the '96 model, but mine have all had a choke system with three settings: Choke On - Automatic (in the middle) - and Choke Off. Normal operation should be in the Automatic mode. It lets you engage the choke from the switch on the controls, and then takes over in Auto mode to slowly open the choke as the motor warms up. Sometimes the choke selector lever back on the motor gets bumped without realizing it, can throw things out of whack.

The thermostat housing is normally below the exhaust manifold cover on the back of the motor. There will be a water hose coming from each bank of cylinders, coming to the cover. Later models have two thermostats under that cover, I usually order the kit with thermostats, gaskets, springs and check valves all together. Not hard to pull apart to check, can be a little tricky getting it all put back together.

Good luck with it, let us know what you find out.

Thanks Mark, I forgot about the choke thing which would make sense with the way it runs. I'll check with him and see what we can find.
Cal

Mark,
The chokes had been replaced by primer systems long before 1996.

There were 2 different 90s in 1996. One was a 60 degree block with the t-stats located in the top portion of each head. These had 4 carbs. The 90 degree block is what Mark had prior. The t-stats are located in the lower rear between the heads. these had 2 carbs.

They all will run rough until they warm up but being sure the carbs are adjusted correctly & the linkage is syncronized will help.

Post a model # for correct answers.---Some of the newer motors also had a "Quick start" feature and if everything is working properly they are nearly a " turn the key " and go motor.