over heating 175 mercury 89 model need help

[clint whidden]

i have completley replaced all gaskets, putin new impeller changed stats and cleaned the pressure release system. it runs fine at idle and as long as i dont go over 35 mph i will not hear the alarm sound. If the alarm goes off i slow down and it cools off and buzzer goes off. Its getting plenty of water and i checked the black grommet that is seated in the pressure release system and it is seated tight no problems there. i dont have a pressure guage so i cant monitor the pressure. a guy told me it could be a timing issue what do yall think please help.

 

[j_martin]

Re: over heating 175 mercury 89 model need help

i have completley replaced all gaskets, putin new impeller changed stats and cleaned the pressure release system. it runs fine at idle and as long as i dont go over 35 mph i will not hear the alarm sound. If the alarm goes off i slow down and it cools off and buzzer goes off. Its getting plenty of water and i checked the black grommet that is seated in the pressure release system and it is seated tight no problems there. i dont have a pressure guage so i cant monitor the pressure. a guy told me it could be a timing issue what do yall think please help.

Spend the 25 bucks or so it takes to get a pressure gauge. That will either prove the cooling system, or show the fault.

You're controlling about a 2 million BTUH fire in that engine. That's enough to heat about 40 average homes in Minnesota in January. Timing or mixture problems can add enough heat to overcome the cooling system. Usually the same faults will cause serious engine damage, so don't play around with it.

hope it helps
John

 

[sschefer]

Re: over heating 175 mercury 89 model need help

John's final line IS the bottom line. These engines will burn up if you don't get it fixed. The one part of the cooling systems you have not checked is the poppet valve. A pressure check might reveal this but if you can't figure out how to do that then just replace it.

 

[clint whidden]

Re: over heating 175 mercury 89 model need help

im sorry i was referring to the poppet valve as the pressure release valve. we have done everything to makesure plenty of water is circulating thru the motor, new stats, poppet valve looks fine there is plenty of water coming out of the motor where it should be were stumped on this. is there any thing else we can try? we ran it without the poppet valve and it ran fine until we got over 35 mph and it would set off an alarm and i slowed down and the alarm turned off. no that we put the poppet valve back in it over heats much quicker

 

[sschefer]

Re: over heating 175 mercury 89 model need help

1. Can you do a compression check?

2. Your engine may still have a rev/limiter or an Advance module that could be blown. If you have what looks like a second alarm module mounted horizontal on the starboard side of the engine, disconnect it and throw it away. Merc doesn't even show it in the parts list anymore. Once you get rid of it, check your max advance timing at cranking speed and then set it subtracting 2 degrees from whatever is recommended. This may not give you all the power you had on the top end but it is a safe place to start.

If this is the case, #1 and #2 can take a beating and #1 will be the first to fail because it is at the far side of the cooling system. The port side is where the over heat sensor is for the alarm module, the starboard head has the temp sender for the temp gauge.
You could swap and maybe get a better idea of the temp rise. I suspect since max advance is hitting about the same time your temp problem is with ref to RPM that it is the module.

 

[clint whidden]

Re: over heating 175 mercury 89 model need help

thanks i will check it and let you know back

 

[j_martin]

Re: over heating 175 mercury 89 model need help

im sorry i was referring to the poppet valve as the pressure release valve. we have done everything to makesure plenty of water is circulating thru the motor, new stats, poppet valve looks fine there is plenty of water coming out of the motor where it should be were stumped on this. is there any thing else we can try? we ran it without the poppet valve and it ran fine until we got over 35 mph and it would set off an alarm and i slowed down and the alarm turned off. no that we put the poppet valve back in it over heats much quicker

You can't tell a couple of things without a gauge.

1. Is water delivery sufficient, ie the tube and gaskets in good shape?

2. are all the small ports in the base clear? I suspect they aren't. Without the poppet, it should have overheated almost immediately at idle. The fact that it stayed cool indicates restriction. I sawed a rotten log in half with my XR4 once. Didn't even feel the hit. Engine overheated in 100 feet. Took me about 4 hours to dig all the rotten wood out of the engine.

Water pressure at different engine speeds is a great clue to what is happening. If the above hypothesis is true, water pressure will be higher than it should.

I agree on the advance module. Anything but the stator, trigger, coils, kill circuit, and one green wire to the oil system connected to the switchboxes should be disconnected till proven good. If a timing module shorts out, for instance, it grossly advances the timing. The max timing without it should be about 22 - 23 degrees. It might be as low as 19 with the module. Leaving it there for testing won't hurt, it'll just take the goody out of WOT.

hope it helps
John

 

[Faztbullet]

Re: over heating 175 mercury 89 model need help

Did you buy it this way or problem suddenly occur? Did water pump fail? Is this a salt water engine?

 

[clint whidden]

Re: over heating 175 mercury 89 model need help

I bought it used. And it's a freshwater rig. Mostly used on lake fork

 

[sschefer]

Re: over heating 175 mercury 89 model need help

Due to a recent discovery of my own, I need to ask if this is a long shaft (20") or an extra long shaft (25"). A V135 XL that I acquired had #1 fried and #2 headed south because of a modification that the P/O did in the Mid Section. These motors have an extension on the water tube that uses a plastic sleeve to join the two pieces. This is one of the reasons that John's pressure tests really pay off because the only other way is to pull the mid section.

I think if you do the tests you'll either find the problem or remove all doubt.

 

[Faztbullet]

Re: over heating 175 mercury 89 model need help

Check out this old post of mine, it has water flow charts
http://forums.screamandfly.com/forums/showthread.php?t=109451