Runnin hot...bah!

[TheTinMan]

Pullin my hair out here. My 98 Merc 200 EFI gets an overheat alarm over 4000 rpm's. I replaced the waterpump, thermostats and the dealer did the poppet but still getting alarm >:(

I replaced a 15 psi water pressure gauge with a 30 psi one, 15 is too low for my motor. I also installed a Faria cylinder head temp gauge and sender.

I launched the boat today to run the Seafoam process....good stuff, try it! I needed to run the boat pretty hard after the Seafoam. Water pressure is WAY too high. The 30 psi gauge gets pinned at only 3000 rpm!

I did get her up to 50mph @ 5600 rpm ;).....and an alarm too! :'( :'( Temp gauge was only reading 145-150F. I really need one of those infra red thermometers that you just point and get a read on all cylinders to see if I'm actually running hot or not. Could just be a temp sensor maybe???

The really high pressure kind of points to the poppet valve not working properly. I have that pulled out and will take to the dealer tomorrow. If that doesn't fix the pressure problem I have a blockage somewhere. I'm hoping that's not the case because I really don't feel like pulling the power head and lower unit off.

Any Merc heads have any ideas? How bout you BigShrimpin?

Thanks

[spareparts]

i think you are on the right track with the sender, pull the sender out and float test it, replace with a new.

[msbhammer]

Sorry to hear of the high temps Tin, Hope it works out for ya.

[Airslot]

How old are the T-stats? They aren't that expensive, 12 each or so, might be worth changing out.

Airslot

[TheTinMan]

thanks, stats are new. :-/

[bigshrimpin]

Tin - My pressure at idle is about 3-5psi . . . 12 - 15 at cruise and 18 - 20'ish at WOT. 30psi is too high . . . something is wrong. I can't see the poppet causing pressure that high . . . Spares is the man here. There was a post about this on S+F a while back . . . about blown head gaskets causing some steam pressure.

http://forums.screamandfly.com/forums/showthread.php?t=42997&highlight=30psi

[spareparts]

if you want ot buy one of those temp guns, Harbour Freight has them for under $50. NAPA sells them for $75, They really are handy to have around. Other wise go to a welding shop and get some temp sticks, they look like a crayon, they melt at a prescribed temp, get one for 150, 175, 200, 225 temps, when your alarm goes off, stick it to the head and see which one melts. Your block pressure seems high, but not knowing the accuracy of your gauge( all instruments are subject to question), I would verify that you do have a heatiing problem first, tehn look at the poppit valve, theres not much in that block to restrict water flow other than the poppit valve. You may have a bad alarm module screwiing with you.

[TheTinMan]

While the head gaskets are definately a possibilty, I don't think so. A compression test should tell me that, correct?

I'm thinking it's an outlet obstruction now. I have a bad feeling I'm going to be removing the powerhead


http://img.photobucket.com/albums/v206/Mnutz/coolingproblemcausesfv5.jpg


http://img.photobucket.com/albums/v206/Mnutz/v6waterflowdiagramib9.jpg

[TheTinMan]

This is interesting too;

http://my.boatus.com/forum/forum_posts.asp?TID=47566&KW=225+EFI

[TheTinMan]

My thread over at "Scream"

http://forums.screamandfly.com/forums/showthread.php?t=120793

[TheTinMan]

You may have a bad alarm module screwiing with you.

I was hoping this was the case but the HIGH pressure I think says I do have a cooling problem.

[Kajun]

tinman...i have the exact same problem.....so far..new thermostats & temp sensors,rebuilt carbs, tonight i'm changing to a complete new water pump...which i doubt will fix it since the one i pulled off was damn near brand new.....next is water circulation for me..

i can run it all day long at 35mph...once i hit 40mph/5000rpms...my overheat alarm comes on......when i touch the heads its cool i can hold my hands on both...water is pumping strong and steady at idle and high speed......think i'm gonna buy a infared thermometer next too........i really hate to start tearing into this thing....maybe i'll just go fishing and say hell with it .. just dont go over 35mph lol

[spareparts]

if the heads are cool, i'd make sure that it is indeed overheating, the sensor for the temp is located in the head, while it is posible for it to overheat in a small area( around the sensor) its unlikely to happen, it could be cooling off before you get the boat off plane and get back to the powerhead to check it. Try this, disconect the sensor wire to the temp alarm( tan/blue stripe I think) run the engine again and see if the alarm goes off again, if it does, and your sure you disconected the over heat sensor, then you've got something else going on

[bigshrimpin]

Tin - did you do a compression test yet? What do your plugs look like?

[TheTinMan]

BS, not yet, hopefully tomorrow (thur.) afternoon. At this point I'm hoping it's a head gasket :-/

If compression is good, before I remove the powerhead I am going to drop the lower unit, remove t-stats and poppet, hook a hose up to the water tube and see if I can flush it out.....sound like a good idea? I figured I could check the waterpump housing too, maybe it's cracked or has a leak and I'm sucking air??? That would cause a crazy psi reading, wouldn't it?

[TheTinMan]

Kajun, is your pressure high too?

[TheTinMan]

What if I was to remove the poppet completely? Will that cause low RPM overheat? I would think it would definately lower the pressure.

Actually, I think that would cause the motor NOT geting up to operating temp at low speed.

[Kajun]

tin...i dont have a pressure gauge or a temp gauge...definetly on the "to do list"

[TheTinMan]

Compression is good, 120-125 psi all across.....all 6 plugs looks the same, a little black oily residue.....probably some carbon left over from Seafoam procedure.

Next step is to drop the lower unit (again) and have a look-see.

Pretty soon and MJ will have more hair than me! :o :-/

[willy]

Thats good though right Tin, if the head gaskets or something else similar were going bad you would not get that good compression. Right ???

[TheTinMan]

At this point I was kinda hoping for a blown head gasket...easier fix than removing powerhead.

[kamikaze]

Tin:

What makes you think head gasket is bad if compression is good all around?

If water is getting into a cylinder then high water pressure could be understood due to compression stroke, but you said plugs are not steamed clean, nor is compression bad. so I don't understand why you think head gasket?

With all the bad head gaskets I seen, water always gets into the cylinder on the power-stroke at least when compression drops and vacuum is formed. Never seen a bad gasket that only flowed one way.

Bite the bullet, it's most likely going to be under the power head in the poppet's

Kamikaze

[TheTinMan]

I know it's NOT the head gaskets, think you misunderstood my post. I have a couple more things I want to try before removing the powerhead, but I do believe I will end up removing to find the blockage.

I can run all day @ 30-32 mph without a problem, it's when I go over 4000 rpm's, which I really don't do, when I get an alarm. But I need to find the problem cause it just ain't right :-/

[bigshrimpin]

Why would you pull the powerhead? I don't understand.

[TheTinMan]

Why would you pull the powerhead? I don't understand.

If I can't find/clear the obstruction what other choice do I have ?

[kamikaze]

Tin:

Roger - I miss understood, although I have an idea that is off the wall but may just help verify what the problem is.

Temporarily remove the water hoses from the top of the heads and block as shown in the picture in your earlier posting and connect a new temporary drain hose with a manual on/off valve that is rigged to drain over the side. Run with the hood off and at speed open the valve. Verify water pressure drops and alarm no longer sounds. ( You should be by passing any blockage that may exist under the power head and the water flow should cool the motor as intended. At least then you'll know it's a blockage for sure vice a faulty alarm or something else inducing the problem.

Kamikaze

[spareparts]

Tin Man, your first post said the temp gauge was showing 145-150, make sure you're chasing an overheating problem and not a grounded out sensor wire. Disconnect the over heat temp switch wire( tan/blue stripe)at the sensor, run the boat and see what happens. The alarm wokrs off of a ground circut, anywhere in the harness, if the wire becomes grounded, it will set the alarm. If the poppet valve is removed, the block will not fill with water completely and create steem pockits. I wouldn't even bother with pulling the powerhead or lower unit till I confirmed the problem is high temp, and not a wireing problem.

[TheTinMan]

It's a PITA because I can't create the problem at home, needs to be running in the water at 4k rpm's plus. It's the PRESSURE and ALARM that makes me think there's an obstruction but I will verify it's not the sensor before I yank the powerhead.

[Kajun]

man..this is like deja vu!

[Seacrets]

Most marine dealers can flush your cooling system and remove any buildup of junk in the water passages. Are you getting water out the pee tube at 140-150. If it's like my Merc 150 you won't.

[phatdaddy]

I had a similar problem on a 83 150 Merc. It turned out to be a broken ring in the middle port cylinder which is just below the temp sensor. I pulled the power head to check the gasket between the base. changed head gaskets and had the heads shaved, etc. While the heads were off ,I was looking up in the cylinders and noticed the ring gap on that piston was about 1/4 inch.
Good Luck.

[TheTinMan]

I had a similar problem on a 83 150 Merc. It turned out to be a broken ring in the middle port cylinder which is just below the temp sensor. I pulled the power head to check the gasket between the base. changed head gaskets and had the heads shaved, etc. While the heads were off ,I was looking up in the cylinders and noticed the ring gap on that piston was about 1/4 inch.
Good Luck.

pd, did you have good compression?

[TheTinMan]

Are you getting water out the pee tube at 140-150.

yes, thanks.

[phatdaddy]

Tin,that was the weird thing, I did have good comp on all cylinders. A mechanic friend said the end of the ring must have broke off and passed out the exhaust. The wall of the cyl looked good. I had some other issues with the engine, so I just re-powered instead of going any further. One thing I did learn is to check your t -stats. I change mine every year w/ the water pump. I take a piece of string and put it in the opening of the t-stat and hang it in a pot of cold water. Put the pot on the stove with a frying thermometer. Turn on the heat and watch the water warm up, when the t-stat drops in the pot, that is the temp it is opening. I have found them to be as much as 20 degrees off. I also like to get two that open about the same time.

[TheTinMan]

pd, what about your water pressure?? I can't see that being high with a bad ring.


I just read the other day about that t-stat test...mine are new.

[TheTinMan]

I'm 90% sure it's an obstruction. I'm going to check the waterpump and housing...it's possible I cracked the housing (maybe over torqued) when installing the new impellor and I'm sucking air. If that's not it I'm going to remove the...what the hell is that cover between the heads called again???

I don't think it's a major engine problem....she runs like a raped ape! :o

[phatdaddy]

Tin , you're right, the broke ring would not have anything to do with high pressure. My pressure was 12 to 14 lbs @ 4000 rpm. The only symptoms I had were after running at 4500 rpm for 25 to 30 minutes, the temp alarm would go off, but the gauge only showed slightly above normal. I would stop the boat and turn off the motor. After 1 minute, I could crank it up and run another 25 to 30 minutes.
I would still test the t-stats, even though they are new. I've had brand new ones out of the box be way off . I've also had better results with OEM water pumps & t-stats than "will fits".

[Kajun]

i found this LU exhaust seal all busted up on mine...think this could cause my overheat alarm? i got one on order today but it wont be here till next week sometime...now i got to wait to see if the new water pump fixed it...or should i just put the LU on with this seal like it is and run it?

http://img213.imageshack.us/img213/3949/mycamerapics034yt9.jpg

[phatdaddy]

Kajun, the mechanic thought that my seal was bad, he said the exhaust would pre-heat the water before it go to the block and cause higher than normal running temp and maybe overheating. Unfortunatly, my gasket was O K .

Tin, I might have missled you with my first post. I never did get the motor to run normal. I lost a season and spent $1,000 on "repairs". I did everything my shade tree experts suggested and finally took it to the local dealer. A week and $700 later he called and said he got it running "cooler". The only thing he noticed was the broke ring. By that time I had had enough, I loved the V-20 hull and wife said life's too short and she missed a summer on the water( She was a teacher then so we took it out 4 or 5 times a week), so I put a new motor on. That was 12 years ago, so I'm due to make that decision again soon. I don't think you have the same problem because of the high pressure symptom

[kamikaze]

Kajun:

Given the corrosion on the lower part of your engine bracket have you given any thought that you might be overheating due to salt build internally within the engine cooling jacket? I have used MST Flushclear
( http://www.mstguardian.com/Treatment.htm and found it quite effective at removing salt build up.

It looks like the company is having some trouble with an employee patent issue, but they might still be selling the stuff? It is rather easy to do with the lower unit already off, just mix the stuff up, fill a pressurized 3 gallon bug sprayer and connect it to water pump tube in the midsection with a rubber plug and fill the engine cooling jacket, let stand for 15 minutes and salts all gone.

Kamikaze

[willy]

Well Tin any updates ???

[TheTinMan]

No, not yet. I'm in no hurry, season is over now for me.

I think I'm going to build an engine stand and take the motor off for the winter. I have access to a huge garage/workshop for the winter. I'll figure it out and fix it ;)

I'm going to remove everything off the transom too. Transducer, speedo probe and swim platform. I want to re-drill the holes (oversized), fill with resin then remount. I may install transducer in bilge. If not, i will 5200 a piece of Starboard and mount to that. Pretty sure my transom is solid...wanna make sure it stays that way. If I'm keeping the boat I want to install Bennett Tabs too.

I would like to remove bowrail too, we'll see.

Calling for 2" of snow here in the AM!!

[willy]

Yea and I will be out standing in for the opening of deer season here.
Tin I removed my bow rail. Glad I did. Looks sweet and accentuates the sweet lines of the boat. Looks like something out of a carolina boat shop.

[phester]

thinkin about that too , Willy, or maybe just lowering it

[Kajun]

well Tinman..i dropped mine in the water last night after replacing my steering cable....first time in water since i hit that sand bar.....so i was finally gonna get a chance to test that new pump....got up on plane and immediately got a overheat alarm ..this time at 25-30mph...strange..i turned around and headed back in...got to dock and took off cowling...engine was HOT...unlike the last times the alarm went off and it was cool to touch....narrowed it down to starboard side for temp switch that went off......all thats left to do now is tear this thing apart and go through all water passageways :( gonna put mine on the stand too and go through it with a fine tooth comb.

[Seacrets]

You don't have to tear your motor apart. I had an Evinrude 185 with the same problems. My marine mechanic pumped a descaler thru the block and made the passages look like new, and it ran much cooler. There are products similar to rydlyme on the market. Google them and you'll see how it works. My mechanic didn't take anything apart on my motor. I'd call around and chat with some marine mechanics before tearing into your motor. Just my $.02

[Kajun]

check out the "alil blockage" post ;)

[Blue_Runner]

Tin - any updates on your issue?