85 Nautique - Runs hot, then won't idle

[nautique99]

Just put the boat in this weekend after a tune up. Runs well on start up. Temp reads 160 until I slow down for the first time. Then gauge goes to 200 and engine won't idle. It quits and needs to have the throttle "goosed" a bit on start up to keep it from dying. Just installed a new impeller.

Also, how do you clean the air filter (spark arrester)? Think that may have something to do with problem?

Thanks!

[83sn2001]

RE: 85 Nautique - Runs hot, then won

Doubt that made it run hot. I would check the thermostat,should be 143. Also, did the impellor have any blades missing. If so you may have a blockage. Check all hose connections as well. Cleaning the arrestor is simple. You can use carb cleaner and spray it on or my preference is to buy a gallon of mineral spirits, pour in a bucket and let it soak for a couple hours.Remove and rinse. The rough running condition may be cause for concern(head gasket or cracked head.Check your oil for water. May want to do a compression check also.

[Mikeski]

RE: 85 Nautique - Runs hot, then won

Change the points.

[JAG]

Runs hot, then won't idle.

Engine temp should always remain approx. 160 when idling. It will run hotter at full throttle and start hot after shutting the engine and restarting shorlty after due to residual heat. Start with inspection of the water intake filter screen, the housing and screen should be clear of debris. Next remove the raw water pump housing cover and inspect the impeller. Unless you know the history of the boat you should replace the impeller. The impeller should have all of its blades and be flexible. the impeller housing should free of excessive deep grooves which would allow water to bypass the impeller blades. Next inspect the thermostat. Again, unless you know the history I would replace it. Another possible cause of overheating is an air leak into the raw water suction line to the raw water pump. Just a slight leak through a hose connection or a hole will result in sucking air in instead of water and therefore an increase in operating temperature.
As far as rough idle goes, Check the points,rotor, & cap. I highly recommend a carb rebuild on any carburated boat every several years. Carb rebuild kits are available from Discount Inboard Marine and are fairly easy to do yourself if you have no experience.