GT-40 over heating

[richard]

2001 Super Air Nautique, have fresh water cooling system,
seldom use last year to this summer but will run the engine with garden hose peroidically,
Last week put to water,start the boat,every thing is fine,running at idle to about 1200rpm head out,
about 5 minutes,smell burning ,open the hatch,see smoke came out from starboard side manifold near exhaust of engine. sitting a while on water ,wait cool down and head back to marina and start checking.
1 )First think the raw water pump, take it out, see from the in-out the impeller are complete, so put to a motor bench test the prime and volume, it can prime and output are strong enough.
2 ) think vacuum leak,checked all hose and camps, strainer, no leak,
3 ) through hull flush kit, no problem,
4 ) thermostat,remove the thermostat,the result is same,
5 ) flush garden inlet, it's no air leak,
I remove the raw water pump and run it with a 2hp motor externally,with a big bucket,direct connect to raw pump output hose,so I don't need put the boat to sea and avoid possible air leak, run the engine,it can be longer time (say 10-15 minute)to become hot,can see plenty water come out of exhaust,first the coolant tank start to becomes hot,and then the heat exchanger, the thermostat housing,
and the exhaust pipe also very hot,if don't stop engine this time,seems the rubber will burn.
* the riser was change 5 month ago. manifold used about 3-4 years in salt water,engine Hr about 1,200
I have no new idea so far, appreciate for valuable advice.

[jhersey29]

The raw water pump just supplies water to the thermostat but you also need a good working circulating pump. Had a heat issue on a very old correct craft mustang and replaced the circulating pump. It was perfect after that. http://www.nautiqueparts.com/enginec...pump-ford.aspx

Sent from my RM-877_nam_att_205 using Tapatalk

[azeus17]

If he has a closed cooling system, the raw pump would cool the exhaust and the circ pump would cool the block. Sounds like two issues. You say the risers are getting hot enough to melt the rubber hose, but how hot is the coolent tank getting? Do you have an IR thermometer? I would try to diagnose the systems seperatly. Take the hoses off the back of the risers to see if you are getting water out of both sides of the engine. It will be loud, but you shouldn't have to run it long. Maybe you have a blockage on that starboard side.

For the holding tank...it can be hard to tell if hot is too hot. I would try to get a temp. Where does the guage read engine temp on a closed cooling system?

[richard]

thanks for the input, the boat has closed cooling system,the raw pump had change been change one time about five years ago due to same fighting with over heat issue but found not relation to it,and it has brass impeller ,not easy out of work, and I can see the coolant flowing on the coolant reservoir, have not thermo gun when checkin,can't say how hot,can't tough by finger,the starboard side manifold much hotter than other side, (found smelly and smoke came out ),riser not very hot, feel near burn on the exhaust rubber tube, supplied cooling water with enough water,(can see exhaust flap water plenty)

[richard]

*for inspecting and ensure enough water flow to cooling necessity without putting the boat to sea for testing,I run the raw pump with a motor bench externally,
*the 2001 Super Air Nautique still in good shape ,
*had suspect the stock through hull flush setting,I replace it with a set up like this.

[richard]

temperature drop lower

Today takeout the riser,manifold and heat exchanger,no significant problem found,remove rust bud build in the the water passage of riser and manifold ,flush out some dirt from the heat exchanger,put it back, test to water, , cruising about 20 minutes,the symptom much reduced! better in higher RPM,in idle feel a bit hot, next day will have look on the oil cooler, what should be the temperature of the heat exchanger ? its hot when I touch, similar to the fresh water coolant tank.

[s_kelley2000]

Sounds like the risers and manifolds were at least part of your problem. If it is running the proper temperature at speed but heating up at idle that usually means there is an air leak somewhere. I know that is true with a raw water cooled system so I would think the same holds true for a closed cooled system like you have. I know you mentioned that you checked all connections for air leaks but I would check each one again. Use a nut-driver instead of a screwdriver to make sure that the clamps are tight. Also check that the strainer gasket is in place and the strainer is tight. If any of those hoses are dried and cracked you may want to replace them because even a small pin hole could cause it to not cool properly at idle.

[richard]

The over heat issue can say solved after flush and rust remove the related sea water passage elements :heat exchanger,riser,manifold, but don't found any element has obvious problem,but on these actions,all the house clamps are re tighted.
Thanks for all your helps.