1989 MARINER 150 OVERHEATING

[prodinet]

I HAVE A 1988 COBIA MONTECARLO WITH A 1989 MARINER 150 HP OUTBOARD. THE ENGINE WORKS FINE, REALLY SMOOTH, BUT WHEN I GET THE REVS UP TO 3000 RPM, THE TEMPERATURE STARTS GOING UP ALMOST AS FAST AS THE REVS! AND I HAVE TO SLOW DOWN. I HAVE CHANGED THE IMPELLER PUMP, THERMOSTATS, TEMP SENDERS/GAUGES, TOOK THE ENGINE APART AND HAD ALL THE WATER AND OIL PASSAGES AIR BALSTED AND CLEANED, CHANGED THE IGNIION ADVANCE MODULE, PISTONS, RINGS, CYLINDER HEAD GASKETS, ETC... LOWERED THE ENGINE SO IT HAS MORE CONTACT WITH THE WATER, AND IT DOES THE EXACT SAME PROBLEM! SOMEBODY PLEEEEEEEEEEEEEEEASE HELP ME! ANY IDEAS ARE WELCOME. THANKS

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

Your poppet valve is not opening...<br /><br />It's under the switchboxes on the starboard side of the engine down low..<br /><br />Take it apart, clean (you may have missed it earlier) and replace the diaphram, spring, gaskets, and maybe even the grommet and carrier...<br />It is designed to open around 2500-3000 rpms to allow more water "flow" thoughout the water passages. If it doesn't you will overheat!<br /><br />Very cheap and easy fix...<br /><br />Take a look at this link..<br /> poppet assembly <br /><br />Let us know...

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

Oh, I forgot to ask, what are your temps above 3000rpms and are you getting an overheat alarm? Because these engines do run hot even at optimal working order.<br /><br />But to add to my previous post, I bet you have some debri/vegetation stuck in the poppet assembly causing your problem... And even more so if you run in salt water....

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

Thanks! I removed the poppet valve since I couldnt find a replacement (it was sunday) and went out to the lake. It does the exact same problem, when the revs get to 2000 its fine, after that the tewmp goes up as fast as the revs (really!) and the alarm goes off. Should I put a new poppet valve on or do you think the problem is something else?

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

You did put the poppet valve assembly back in correct.... <br /><br />Was it dirty, clogged with debri?<br /><br />We need more info...

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

The poppet valve was very dirty, with a lot of debri, I just got a new one today and will test the boat on sunday, I hope this works! Ill keep you posted...

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

I think that is your best option as of the info we have.. The symptoms match exactly with a faulty poppet valve that will not open...<br /><br />There could be other causes but this is the easiest to fix...

 

[AndyL]

Re: 1989 MARINER 150 OVERHEATING

If you ran it without the poppet valve I would have thought it would certainly have overheated as you would be dumping all your cooling water back out of the exhaust. The temp senders are located at the top of the block and I doubt you would have had enough head of water in the block to get that far. KCLOST is spot on with his daiagnosis.

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

I tested the boat on Sunday, with the brand new poppet valve, I installed it just how the manual said. It still overheats! The exact same problem, the temp goes up just as fast as the revs. I cant use this boat. It has a new impeller, poppet valve, , thermostats, temp sending units, pistons, rings, the block has been air blasted for debri. Anyone have any ideas? or a match and gasoline...

 

[AndyL]

Re: 1989 MARINER 150 OVERHEATING

I have read somewhere in this forum of someone having similar problems and his final solution was to cut a couple of turns off the Poppet spring. If you still have the old spring you took out you could try cut that one down a bit which would allow the water to flow through the block at less pressure. May be worth a try as an experiment unless someone with more knowledge would like to come in here and say its not a viable route. There has been heaps of discussion regarding Poppet valves which you will find if you run a search in this forum. Don't give up!!<br /><br />Andy

 

[studlymandingo]

Re: 1989 MARINER 150 OVERHEATING

WillyBWright mentioned in another forum about deposit build-up inside the cooling system causing overheat symptoms. Do you have any scale inside the cooling ports?

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

Are the splines of the impeller bent in a counter clockwise direction (if you were looking at it from the top)? <br /><br />The other suggestion is the top of the pick-up tube not sealed or has some corrosion...<br /><br />Let us know...

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

Everybody thanks for the help! I cut two of the turns off the poppet valve spring and went out for a test drive, nothing improved. I finally got despaired and took out the poppet valve completetely from the engine and tested it like that... it finally worked! a lot of water just pissed out of the poppet valve opening and I was able to use the boat at full speed as long as I liked and the temp stayed at the 1/2 mark. Obviously this is not a permanent solution since I cant just leave the poppet valve hole uncovered, but maybe this might give you guy a clue as to what is wrong... By the way, when the poppet is installed, there is very little water coming out of the pissing hole after 2500 revs. Not much pressure at all...

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

I am going to replace the impeller tomorrow just in case (althought I bought it a month ago and the mechanic installed it..he might have installed an old one or installed it wrong... Does an impeller get ruined if you start the engine a couple of times without water? Also, is there a little bit of water spray supposed to come out of the exhaust ports when you get the revs past 2500 ? Mostly out of the left side exhaust port (looking at the engine from the rear)

 

[prodinet]

Re: 1989 MARINER 150 OVERHEATING

I took off the stats and checked the cooling ports for scale and debris and everything looks clean, I will try the engine without the stats... is this a good idea?

 

[KCLOST]

Re: 1989 MARINER 150 OVERHEATING

"I finally got despaired and took out the poppet valve completetely from the engine and tested it like that... it finally worked! a lot of water just pissed out of the poppet valve opening and I was able to use the boat at full speed as long as I liked and the temp stayed at the 1/2 mark."<br /><br />That tells us that the poppet valve was not opening, and is, or part of your problem.<br />But you need it in there because the engine will overheat at low rpms below 2500 if it is not installed and closed. The poppet should open at 2500-3000 rpms to relieve water pressure in the block and increase water flow.<br /><br />"Does an impeller get ruined if you start the engine a couple of times without water?"<br /><br />Absolutely!! If you have run the motor without water replace the impeller. I would replace it even if you haven's. I wish you had a water pressure guage, you could just have low water pressure throughout the cooling system causing poor water pressure and flow. Replace this first and retest with the poppet installed properly. Leave the t-stats in.<br /><br />"Also, is there a little bit of water spray supposed to come out of the exhaust ports when you get the revs past 2500 ?"<br /><br />Past 2500rpms the poppet begins to open and the excess water is dumped into the exhaust where you will see water exit the upper exhaust ports. Without your poppet installed you may see water exiting the ports at all rpms levels.