89 150HP XR4 Overheating at Idle

[Jpinner]

When Motor is warmed up and idleing or when running through no wahe zone at low rpm, water stops coming out of the hole and steam begins to come out. If I leave it continue to idle it will overheat. Water pumps out at high rpm. My mechanic has changed the water pump, thermostats, and cleaned the cooling system. He did find wood and sand in the cooling system. He says there are parts of the cooling system that are inaccessible and cannot be cleaned and that my be the problem. Any suggestions?

 

[The Marine Doctor]

Re: 89 150HP XR4 Overheating at Idle

Sounds like the Poppet valve is plugged or to stiff.<br /><br />TMD

 

[trumanlake]

Re: 89 150HP XR4 Overheating at Idle

does it overheat at high rpm's? if not i would jump on the poppet valve. if it is stuck open or leaking (not sealing) it would get hot idling.

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

I checked the poppet valve thoroughly and it seems to working fine. There was no visible debris stuck in it.

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

It does not overheat at high RPM. When it overheats, I would increase the RPMs and the alarm will stop when water starts to flow.

 

[trumanlake]

Re: 89 150HP XR4 Overheating at Idle

just curious, are those one or two piece heads?

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

Trumanlake :<br /><br />I beleive it would be two piece, there are two heads each with 3 cylinders. It is a V-6. I,m not a mechanic but I think thats what you wanted to know??

 

[trumanlake]

Re: 89 150HP XR4 Overheating at Idle

ok, let's try this. where is the heat sensor located. below spark plug #1 or to the side.

 

[KCLOST]

Re: 89 150HP XR4 Overheating at Idle

Jpin,<br /><br />Try running the engine with the thermostats removed... There are two of them, one at the top of each head where the water hoses exit... Lets see if that makes a difference...<br /><br />If your water pump is good and flow stops at idle that could be a cause... Are you sure that the impeller on the water pump was installed properly?<br />Just checking...

 

[CU2NITE]

Re: 89 150HP XR4 Overheating at Idle

You say your mechanic checked your cooling system, did he check behind the heads? There is a water jacket on the outside of the head, in order to check this you need to pull the jacket cover on each side, check for obstruction and replace the gaskets. To check the water passages behind the heads you need to pull the heads, check for obstruction and replace head gaskets. Just wanted to make sure he checked all areas around the heads. Also if you do try takeing out those stats to see if it runs cooler, make sure you replace them or you may warp the heads. Just my two cents worth. Good luck and let us know.<br />CU<br /><br />--------------------<br /><br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

Trumanlake: The heat sensor is located under plug #1. CU2NITE: No the mechanic did not pull the heads or jacket covers as far as I know. I sent for water pump kit. I'm going to attempt to change it myself.

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

When changing the water pump is there any thing particular I need to be careful of. I,m using a Clymer Shop Manual.

 

[KCLOST]

Re: 89 150HP XR4 Overheating at Idle

When you replace the water pump, there are two main concerns (or important issues). After installing the new impeller on the shaft (with the key) the pump housing will not just slide down over it... You need to turn the drive shaft clockwise and push down on the pump cover (be easy, don't want to damage the impeller). This will align the impeller blades in the proper direction and ensure that you get the proper amount of water flow.... Just follow your manual...<br />Check the direction of the blades of the impeller when you remove the old one... Looking DOWN on the impeller they ALL should point in a counter clockwise direction and not be broken or cracked...However, most likely the impeller will remain in the pump cover when you slide it up the shift shaft during removal... So if you look at it upside down they will go in the opposite direction, Keep that in mind. <br />The other issue is when you reinstall the lower unit.. I'm going to tell you right now, to get some help... You need to realign the drive shaft up into the crank. Meaning you may need to turn the flywheel to get the splines at the top of the shaft to line up... You can't do this by yourself while pushing up on the lower unit.. Also lining up the shift shafts can be tricky... You will get the drive shaft lined up first, after that be careful not to push the lower unit all the way up until you get the shift shafts lined up... Otherwise you could push the upper shift shaft up and have to start all over... You will probably easily see what I'm talking about when you get to it... Don't be afraid...

 

[CU2NITE]

Re: 89 150HP XR4 Overheating at Idle

Putting the lower unit back on for the first time is kind of tricky, it helps to have someone hold it while you line up every thing. If the unit doesn't slide back in turn the flywheel clockwise until it slides up,(I use a screwdriver and push on the teeth) also make sure your shift shaft is back in it's hole, otherwise your gears wont engage. As far as the pump, look at the schematic in the clymer manual, it is fairly detailed. If there was debris in the lower part of the cooling system I would bet there is some in the upper part, like I described earlyer.(I am going off of the design of my motor, 85 150 merc xr2) you can get schematics of you motor at www.dougrussell.com Good luck and let us know.<br />CU<br /><br />----------------------<br /><br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[trumanlake]

Re: 89 150HP XR4 Overheating at Idle

the reason i was asking about the sensor: since it is below #1 plug you should have the two piece heads(type I). as cu2nite said you may want to check under the cylinder covers and look for obstructions. don't assume that new thermos are good, had 2 brand new out of the box mercury thermos that were bad(would not open!) check them!!!!!

 

[Jpinner]

Re: 89 150HP XR4 Overheating at Idle

I pulled the lower unit down and disassembled the water pump. The old impeller doesn,t look very bad. There is a divider plate between the exhaust chamber and the water pump. It moves up and down slightly and I noticed that it has been caulked with what looks like silicone. What is its purpose and why do think it has been caulked??

 

[KCLOST]

Re: 89 150HP XR4 Overheating at Idle

I assume you are talking about the water pump base (a black nylon?plastic piece at least a 1/4" thick, if so that baby should not move at all, once everything is back on and screwed down. I don't know if silicone should be there...<br /><br />Take a look at this site and tell us exactly what part you are referring to...<br /><br /> http://www.dougrussell.com/partscat...rList=9,7,3,2,13,10,14,11,4,8,17,24,18,25,0,2 0,21,22,12,23,15,19,6,16,5<br /><br />This is a schematic for XR4's...

 

[CU2NITE]

Re: 89 150HP XR4 Overheating at Idle

I thought the same thing the last time I had my lower unit off. The only thing I can think of that could be it's purpose, is getting to the base houseing on your pump. I am sure the silicone(mine has it to) is to keep exaust from entering the water system. Enyone else have an idea on the purpose of this 3 inch metal divider right next to the water pump base? <br />CU<br /><br />----------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[The Marine Doctor]

Re: 89 150HP XR4 Overheating at Idle

That divider is to siliconed to keep the exhaust from entering the waterpump area. I will cut down the flow of water if it is able to get into the pump.<br /><br />So...Silicone the divider..them push the gearcase up into place.<br /><br />TMD

 

[KCLOST]

Re: 89 150HP XR4 Overheating at Idle

CU,<br /><br />What is this divider you are talking about... Look at that schematic and tell me what part# you are refering to... I'm lost...