Engine temp??

[Fman]

Hmmm.. this sounds odd, I hope it works for you. Keep us posted, I have drained my heater every season for the past three years and never developed an "air pocket". I just simply reconnect the hoses. Someone please correct me if I am wrong, but the system should automatically push any air out with the force from the impeller pushing the water through the entire system???

Have you checked to make sure the T-stat is not sticking? What temp T-stat do you have in the boat? I believe you should have a 160 in there, at least this is what the Indmar 340/Monsoon 350 are using.

[docdrs]

Well just got home from Pheonix the guys at AWS were good guys, they found that after I winterized and blew the water out of the heater and when I ran the boat recently it had a air pocket in the heater core. So to all that have the heater you should prime by pulling both hoses off t/stat housing and using water hose in one till you get good flow out the other then put back on. Sucks I had to drive 7 hrs one way to find this out but got the warranty swapped and all good now. Ready to hit the lake this weekend.

Well, thats a new one. How would an air pocket in the heater cause the engine to overheat? Water flows out the block , to the heater , then back to the recirc pump. Thats the reason when you have these boats on a hose or fake a lake with 45 degree house water its tough to get the engine above 140. I hope someone can explain this one Lucy. I would put a ball valve just after the hose coming from the block and when it happens again close it and see what happens .

Now my explanation is with a hot engine when you slow down to idle hot water is flowing thru the heater into the circ pump and this hot water gets sucked back into the engine as the thermostat opens creating a heat sink and immediate rise in temperature. When you idle up the engine, cold water pressure and flow overcomes/dilutes the heater hot water and you get immediate cool down. If you just leave it , idle low, the temp will come down slower but it will come down as the impeller flow is much reduced at the low idle.

To test this theory all you have to do is .... once the engine is well warmed up and hot stop and watch your temp, when it spikes time and record the rate and extent of change, repeat to confirm. Now put a needle nose vise grip on your block heater hose and repeat and see what type of change there is. I will do this test this weekend and report back my results. I am curious as to what if anything will happen. I do have my suspicions.

[docdrs]

The cat engines run hot and Indmar has been making thermostat housing changes to accommodate. Maybe a larger direct port to the circ pump is needed?

[jdub667]

Ok so i have the same asumptions as you all but at the dealer we pulled the t stat put in bowl of water worked fine put back in ran just like at the lake you could hear and feel air in the hoses making a popping noise and could feel at the t stat housing and got hot. Looped heater hoses and ran no noise and could not get over 165 at all rpm ranges. So I primed the heater by filling one side till it came out the other and hooked backe up. Now I will know for sure at the lake this weekend but hopefully it is cured. However when i was priming the heater it took quite awhile to fill and i noticed the hoses go in the bottom of the heater box not sure if this matters. But they said even the new master crafts and nautiques they have had the same issues and said they prime them on the lake per the way everything is routed. I will give update after this weekend..

[jdub667]

Well just got home and the boat worked perfect ran between 140-160 all day, so the heater was the problem. Only thing I can think is that the hoses run into the bottom of the core so it gets a air pocket in the top and cannot flow, easy fix priming at home with hose. Pretty ironic my brothers MB Sport he didnt winterize the heater and cracked the core and flooded his boat, his is much harder to get to than mine but we bypassed the heater and was able to use the boat through the weekend. Not sure how much one is but probably not cheap.

[docdrs]

Thats awesome, I didnt get out last weekend but am looking forward to trying this in the future