Mercury XR4 Overheating - how to fix

**f6noob** · 08-01-2009, 03:14 PM

Hi,

I've seen some threads with the same issues - not sure how to proceed to start from the ground up.

1989 Mercury XR4 150HP.

It will overheat on idle - always at half on temp, then goes past 3/4 up to warning then the beep comes on. If I open her up at a consistent rate, temp falls. I see the water coming out of the pee hole - it's warm but not scalding. I replaced the 2 thermostats 2 years ago, and it's only seen around 4 hours of water time since.

What is the first step seeing as how the temp does drop if i'm moving fast enough - is this indicative of an impeller problem?

Should i run without the termostats for a bit? I'm not super techy, and i don't have a water pressure gauge installed - but i learn fast - is it easy enough to hook one up?

Overheating - what's the proper procedure - shut it down when it beeps continously or go fast and let it cool down?

Thanks - finally have a week of holidays and want the boat to work, i spent the last month replacing the floor...

**j_martin** · 08-01-2009, 06:37 PM

Water pump maintainance should be an annual item in the spring, regardless of hours. They can get fuddled up just sitting.

Pay attention to all the gaskets, including the base gasket. The bottom plate is a wear plate, and should be smooth, not grooved. Housing should be smooth and not distorted from overheat. Outlet gasket should be good, might as well replace it for a coupla bucks.

The best tool for diagnosing the rather Rube Goldberg cooling system in a Murkery V6 is a water pressure gauge. I'd bet the pressure is near 0 at idle.

hope it helps
John

**f6noob** · 08-01-2009, 07:04 PM

John,

Thanks for the tips. Being a total noob how do I test the water pressure - what should it be and what maintenance is required on the water pump (i guess what you described is done on the water pump??)?

**j_martin** · 08-01-2009, 07:18 PM

Install a water pressure gauge on your boat. It's about 25 bucks, and most of us consider it indispensible for keeping a motor alive. It generally goes through a set of standard gyrations as the various features of the cooling system work.

Replace the impeller and gaskets, and look at the other stuff I mentioned.

Get a genuine mercury maintainance manual for your engine. You'll need it.

Most of the questions you have been asking have been covered multiple times. Use the search function and do some reading.

hope it helps
John

**f6noob** · 08-01-2009, 07:27 PM

thx - searching now - have a great weekend. I appreciate it.
Cheers,

Jim

**bobthebuilder** · 08-01-2009, 07:34 PM

Mercs are tempramental about this thing. It has a popet valve on starboard side of motor. Remove it all. You will need some gaskets and maybe a whole kit for it is a good idea. Use some silicone rtv on the very edge of the diaphram where it seals to the top piece which has a weep hole in it. Not a lot of rtv but a thin film only. Also a dab on the screw holding diaphram to the popet valve. If this thing is letting water dump too fast it will run hot at idle. 95% sure this is your problem....... I will check back to see how it works out for you.................. Bob

**f6noob** · 08-01-2009, 08:11 PM

thx - got a morning project now. let you know how it runs. Cheers,

Jim

**f6noob** · 08-12-2009, 08:14 AM

just got a water pump repair kit - now i'm going to attempt this ASAP. Thanks - i'll let you know what was wrong.

**Powmer** · 08-12-2009, 08:54 AM

If the water pump kit does not do the job, remove the thermostats and check temp. Also, flush with the hose fitting and check water flow.

**f6noob** · 08-12-2009, 09:59 AM

arrrgh - ok - i've got the bottom off and everything is going good until one part falls out and I don't know where it goes - it is a little flat piece of metal 3/4 inch long with a goove on one side, bump along the length of it apposite the groove. i think it goes in with the impeller because it came out of there when i removed the cover of the old pump. The shaft has a flat spot on it that this looks like it could fit up against but i want to make sure.

It's kind of a razor blade shaped of metal. Thanks...

**f6noob** · 08-12-2009, 10:00 AM

think i may have figured it out - video on youtube helps... goes up against the shaft and impeller fits over top - apparently.... wow - how does the impeller fit in that pump! LOL. keep you posted.

**f6noob** · 08-12-2009, 10:59 AM

one more tip if anyone is online - i'm re-attaching the bottom end and can't get it to attach all the back up - any good tips for getting it to slide all the way back up? I've turned the prop trying to get it lined up and it slid up a bit more - i have the water pump lined up, the spindle at the front lined up and now i can get a few bolts on but i don't want to crank it ....

**Powmer** · 08-12-2009, 11:39 AM

Fit the key, (flat piece of metal) in the impeller, slide impeller down to the housing. Make sure the lower unit is in neutral, turn impeller and shaft clockwise, while pushing down and the impeller will rotate into the housing. When reattaching lower unit, make sure to have motor in forward gear, and lower unit in forward gear, ****pull kill switch**** slide lower unit up into motor, making sure gear shift rod is in place, then turn prop very slowly to align drive shaft with motor. It should slide up and in. Make sure water tube is aligned. Tighten bolts ever so slightly while moving shifter, if drive shaft is aligned, water tube aligned, the shift rod may be misaligned slightly.

**j_martin** · 08-12-2009, 11:54 AM

I usually have my honey on a strong arm on the flywheel nut. When I get the foot all lined up and the driveshaft started into the crankshaft, she slowly turns the engine over and clunk, in she goes. Then she's there to hand me bolts as soon as I get done cussing about my mashed thumb.

**f6noob** · 08-12-2009, 12:12 PM

success - ok - it was the front spindle that was holding me back - got that lined up and it's all attached - i attached the ear muffs and ran it - instant pee stream vs the intermittent from before - i'll take it out and see if it stays cool. I replaced the thermostats last year but if still hot I'll test those. thanks everyone

User Tag List

Thread: Mercury XR4 Overheating - how to fix

Thread Tools

Display

Mercury XR4 Overheating - how to fix

Overheating at idle speeds

Tags for this Thread

Posting Permissions