Cooling problem 302 Mercruiser 888

[kfraser]

This is a project boat that I just got running. I just replaced the water pump impeller and housing in the lower unit last week. Ran the engine for about a half hour and she never got above 140 degrees. I just bought a new distrubutor and installed, fired it up and she shot up to 190 degrees with no water flowing from the lower unit out the prop. I'm going to pull the engine this weekend to put in a new floor and rebuild the bilge area, just wanted to get some ideas on where to look next for the cooling issue. Thanks in advance...!<br /><br />Kevin Fraser<br /> http://www.shareaproject.com/pages/projectTut,p,116,00.html

 

[Boomyal]

Re: Cooling problem 302 Mercruiser 888

Originally posted by kfraser:<br /> I just bought a new distrubutor and installed, fired it up and she shot up to 190 degrees with no water flowing from the lower unit out the prop. http://www.shareaproject.com/pages/projectTut,p,116,00.html

Huh?!

 

[kfraser]

Re: Cooling problem 302 Mercruiser 888

Huh What?

 

[Boomyal]

Re: Cooling problem 302 Mercruiser 888

Originally posted by kfraser:<br /> Huh What?

What does the distributor have to do with overheating and did you have the muffs on with the water turned on? <br /><br />If so you'd have water running out the prop whether the engine was running or not, unless your impeller disintigrated and packed up the passage ways.

 

[kfraser]

Re: Cooling problem 302 Mercruiser 888

The distributor has nothing to do with cooling. My point was that the last time I ran it, it was working fine. (about 4 days ago) I installed a new distributor and when I ran it again, it is now over heating. The impeller and housing were just replaced last week. Yes I had muffs on it, and believe it or not the water was on. And so your telling me that the water from the muffs is going to force its way through the impeller, up the water supply shaft, through the water pump on the front of the engine, through the motor, then through the manifold & risers and back through the exhaust and out the prop. Just want to make sure I'm clear.....

 

[Boomyal]

Re: Cooling problem 302 Mercruiser 888

Originally posted by kfraser:<br /> And so your telling me that the water from the muffs is going to force its way through the impeller, up the water supply shaft, through the water pump on the front of the engine, through the motor, then through the manifold & risers and back through the exhaust and out the prop.

Yes, if the muffs are on securely. You should notice no difference at the prop whether the motor is on or off.

 

[Peter J Fraser]

Re: Cooling problem 302 Mercruiser 888

You should check the thermostat and the block recirculating water pump as either of these may be faulty after sitting for a long time.<br />Worth checking also that the temp gauge is actually seeing what it is telling you.<br /><br />Peter

 

[steve n carol]

Re: Cooling problem 302 Mercruiser 888

Boomy, I think you hit a nerve...sl

 

[kfraser]

Re: Cooling problem 302 Mercruiser 888

Thanks Kewi, I replaced the thermostat and gave her another try. She is most certainly heating up.. I'm going to pull the engine tomorrow and it will be out for some time. I'll check the manifolds, risers, and put a new water pump on the engine while I have it out. When it does go back in I'll follow boomy's instruction and use a vice to clamp the muffs on.

 

[arfaname]

Re: Cooling problem 302 Mercruiser 888

Firstly, the ignition timing of an engine can effect the running temperature. By changing the dizzy you may have your timing set differently.<br /><br />as far as the water flowing continuously through the engine when not running you will seldom in my experience get a good enough seal from muffs to create this. Water will most certainly flow through the engine alot easier when its running.<br /><br />Id be checking (with the engine running for short periods) the flow of water into your engine starting at the first accessable point on your rubber hoses running to your engine. ie: check the outlet from your leg if it runs an internal impellar, if not then check the output of your external raw pump. Keep following your water circuit until you find a hole that something should be coming out of that isnt. Keep in mind to only run it for very short periods. <br /><br />any chance your impellar is back to front?

 

[kfraser]

Re: Cooling problem 302 Mercruiser 888

Arfaname, Thanks so much for the reply. When I restarted the motor I had the timing light hooked up and it was about 10 degrees off correct setting of 10 BTDC. I lined it up right on the mark. I'm certain the impeller is correct, as I checked the rotation at least four times before I put it in. I didn't want to drop that lower again. As far as water flowing through the engine from the muffs while not running, I have never seen this either. Thank you for pointing out the the supply line removal. I didn't get a chance to pull the engine this weekend, so I'm going to put a barrell under the lower unit and fill it with water. This way there will be no pressure at all from the muffs. This should be a sure way of telling if it is an impeller problem or further down the line. Thanks again for pointing this out.

 

[lowshovel1]

Re: Cooling problem 302 Mercruiser 888

I don't know 1st hand but have read in this forum that a barrell ain't the way to go.

 

[Haut Medoc]

Re: Cooling problem 302 Mercruiser 888

It doesn't matter which way you install the impeller, it will right itself the first time you start the engine......Take off the hose that comes from the transom to the block, start the motor and verify that you have water flow.....Do not run it long or you will fry the rubber exhaust boots.....Once you have verified water flow you can now rule out the drive....I don't see anywhere in this post whether you are FWC or RWC. If you have water getting in and no water getting out, I would look at the water dumps on the risers, they are most likely clogged with scale, thus restricting flow and causing overheat. This may happen again when you actually use the boat or even before that depending on the condition of the block's/manifolds'/risers' innards.......JK

 

[Haut Medoc]

Re: Cooling problem 302 Mercruiser 888

Oh, and you can run it in a barrell, but you will shorten the life expectancy of your impeller......JK

 

[arfaname]

Re: Cooling problem 302 Mercruiser 888

Originally posted by J.kopec:<br /> Oh, and you can run it in a barrell, but you will shorten the life expectancy of your impeller......JK

why is that?? How is having the leg submerged in a drum different to having it in the lake? As long as you do not have it turning over the same water for too long (mine will take a good 20 mins to warm up the tub) it will not overheat. <br /><br />Not being smart here just curious as I have been told this before yet fail to see why its an issue.

 

[Haut Medoc]

Re: Cooling problem 302 Mercruiser 888

Arfaname, you are probably right, it probably doesn't matter that much if you don't run it for long periods of time. I would think that running in the same heated water & exhaust gases would have some affect on the elasticity on the rubber impeller,however I have no scientific evidence to prove that true, and if I had no source for the 'muffs', I would use a barrell in a heartbeat. That is actually my off-season situation, but I change my impeller at the beginning of each season anyway.....JK

 

[mkast]

Re: Cooling problem 302 Mercruiser 888

After you replaced the drive impeller, did you run it without the water turned on? Couple of seconds of running without water and your new impeller will be toast.

 

[kfraser]

Re: Cooling problem 302 Mercruiser 888

After I installed the impeller, I made sure I had water supplied the the lower. Still haven't had a chance to check water flow from the lower unit at the engine water pump. I'll check it tomorrow and give an update. I'm thinking it is in the manifolds or risers....???<br /><br /><br />Kevin F.

 

[Haut Medoc]

Re: Cooling problem 302 Mercruiser 888

Could be but you need to verify water flow from the outdrive first....JK

 

[Haut Medoc]

Re: Cooling problem 302 Mercruiser 888

K, You never went any further with this thread....JK