They said you guys were good...riddle me this. Odd Mercury overheating problem PICS

[Nevek]

Lets start from the start. I bought a 1976 Boston Whaler with a 1988 Mercury 45hp, Pro Fifty model, 2 stroke and 4 cylinders. It didn't start right away but after a little tinkering it started and ran great. I took it out on the lake for a test and it idled great, started fine, and was pretty quick! After 40 seconds of running though I got a overheat alarm. As soon as you slow down and get the boat off a plane the alarm goes away. I then brought the boat home and put in a new thermostat, wear plate and the 2 gaskets that go above/below the plate. Then I took the boat out for another test but unfortunately I had the same overheat alarm.


I did a compression test and had (from top to bottom) 123, 128, 128 and 120. Then I took the videos you see below which may show my issue. I removed the lower unit and back flushed the engine with water from the hose from the top of the block through the water tube. After doing that a little I plugged the water tube, and tried to fill the block with vinegar in hopes of breaking up any salt deposits that might be in there. Most of it came out the exhaust and im not sure how effective it actually was. Then I back flushed again, then flushed from the water tube back out the tell tale hole.


It looks like the issue may have been with my impeller install as I dont remember water shooting out the top of the LU like that and it looks like I have some sort of exhaust leak. I posted pictures of most of the seals and I was hoping you guys could point out which ones are wrong.


Video 1:


Might be the source of my issue. I didn't notice this before because I was running the boat in a barrel and then in the ocean. Water flowing out from where the lower unit mates up to the mid section. How does this even happen? Where is it leaking from/pressurizing the midsection?


201305221804312_zps3f5e2a23.mp4 Video by blueovalstanggt | Photobucket (http://s50.photobucket.com/user/blueovalstanggt/media/2013/Mercury%2045/201305221804312_zps3f5e2a23.mp4.html)


Video 2:


Shows the stream building when the engine revs, then a close up of spray leak #1 which I am assuming is fuel because of the way it pulses. Maybe this explains why it doesn't seem to idle as well as it used to and stalls. Then, I go to the other side where you can see fuel (i assume) leaking from the carbs. Can't tell where it is coming from. When I prime the fuel bulb fuel will shoot out of the bottom carb once I build pressure. Maybe related? Then the engine dies at idle.


201305221811032_zps6722a697.mp4 Video by blueovalstanggt | Photobucket (http://s50.photobucket.com/user/blueovalstanggt/media/2013/Mercury%2045/201305221811032_zps6722a697.mp4.html)


Video 3:
Looks like I have an exhaust leak or something as this gunk is leaking out of the area where the lower unit meets up with the mid section. Short video but if you pause it you can see what I am talking about. What's the deal here?


201305221812512_zpsb0b47210.mp4 Video by blueovalstanggt | Photobucket (http://s50.photobucket.com/user/blueovalstanggt/media/2013/Mercury%2045/201305221812512_zpsb0b47210.mp4.html)








Random stream out the side which I don't believe is normal


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040234_zps6ab02f8f.jpg


Goo leaking out the side
http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040237_zps1af72df3.jpg


This little piece was on the inside of the exhaust...I'm hoping it came from the cooling system


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040244_zpsadc45a21.jpg


Is this seal in the right place(question 1)?
http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040245_zpsd3aff999.jpg


How about these (question 2)?
http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040246_zps8fb0b8ab.jpg


Running vinegar through the block
http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040250_zps693fcfc5.jpg


This is where I am now. I pulled the powerhead but unfortunately I haven't found anything obvious being wrong.



http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040302_zpsbe6d33d2.jpg


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040300_zps66a78c28.jpg


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040298_zpsc8ce819f.jpg


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040295_zpsa5088979.jpg


http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/P1040294_zps933e200d.jpg

Somehow water is filling up my midsection and I can't figure out why. Any ideas?

[Forkin' Crazy]

Is that a crack in the lower where the water is coming out? If before the water pump, it will pump water while submerged, but soon as you get on plane it will suck air.


Watch that prop running in gear like that. They are pretty tough on flesh!

[muskamoot]

There are 2 gaskets for the exhaust plate that both need replacing,one is still mounted on the powerhead,they will short circuit your cooling water if they leak.The new gaskets should direct the water through the exhaust tuner and out of the prop instead of outside it like it is now.The spray appears it may be a bad poppet valve,but it's hard to see.Some smaller mercs don't have a poppet,but if yours does,put a kit in it.The carb leak appears it may be a missing gasket on the bowl nut.

[Nevek]

Is that a crack in the lower where the water is coming out? If before the water pump, it will pump water while submerged, but soon as you get on plane it will suck air.


Watch that prop running in gear like that. They are pretty tough on flesh!

It's actually not a crack. That is where the lower unit meets up with the midsection. There is no crack, but a slight relief (maybe for a screwdriver if you needed to pry the lower unit from the midsection? and water comes out. The water pump housing is directly behind that as you can see in the picture directly below that one.

About the engine in gear, it actually wasn't. When I saw it in person, I thought it was the water/exhaust fumes that were forcing it to spin while in neutral but there is actually very little water that comes out( I think it just starts filling up the mid section and comes out of the relief I just mentioned.


There are 2 gaskets for the exhaust plate that both need replacing,one is still mounted on the powerhead,they will short circuit your cooling water if they leak.The new gaskets should direct the water through the exhaust tuner and out of the prop instead of outside it like it is now.The spray appears it may be a bad poppet valve,but it's hard to see.Some smaller mercs don't have a poppet,but if yours does,put a kit in it.The carb leak appears it may be a missing gasket on the bowl nut.

Great, this is what I was hoping for. I had guessed it was these gaskets but when I took the powerhead off it wasn't exactly obvious. This motor doesn't have a thermostat nor a poppet valve.

[Capt.Insane-o]

The mid is supposed to fill with water, where the water is coming out is damaged by corrosion or where someone tried to pry off the lower unit, or both. There is a rubber seal that fits inside the lower to seal the exhaust tube in front of the water pump. Those motors need the impeller changed every year, check to see that the water tube isn't corroded through and the grommets that seal it on each end are in good shape, then move on to the exhaust divider gaskets.

[TEXAS20225]

Nice avatar Lynn

[Nevek]

The mid is supposed to fill with water, where the water is coming out is damaged by corrosion or where someone tried to pry off the lower unit, or both. There is a rubber seal that fits inside the lower to seal the exhaust tube in front of the water pump. Those motors need the impeller changed every year, check to see that the water tube isn't corroded through and the grommets that seal it on each end are in good shape, then move on to the exhaust divider gaskets.

The entire midsection is supposed to fill with water? Or just the exhaust tube? How does it get out? There is not corrosion, but i guess it is damaged from prying. Can I seal this up with something?

Water tube and bottom grommet checked out. Top grommet is getting replaced. When you say exhaust divider gaskets, do you mean the one on the port side of the engine on the exhaust manifold? Or the ones that connect the powerhead to the midsection/stack thing?

[Capt.Insane-o]

Nice avatar Lynn


Groupe B baby!


Nevek, the plate and two gaskets under the exhaust cover on the block, of course you will need a base gasket. The water in the mid section drains out through the idle reliefs and exhaust reliefs on the lower.

[CharlieB53]

While you have the powerhead and LU off, stick a garden hose to the transfer tube and watch the adaptor plate, see the water passage?

Make sure this passage is clear, no chunks of a prior impeller restricting flow.

If the gasket fails here cooling water will drop straight into the exhaust and out the bottom.

I like to take a sharp punch and lightly tap a line or two across that area between the cooling water and exhaust. Do the same on the bottom of the powerhead. The 'dots' don't have to be hard, just enough to provide a slight 'tooth' so the gasket cannot slide. You do not want craters with sides raised so much they interfere with the surfaces coming together.

[CharlieB53]

That pulsing leak under the ignition plate needs attention. it may be at the case parting line, hard to see.

Stick your finger in there, is that fuel? If so there is a definite fire hazard.

[Nevek]

While you have the powerhead and LU off, stick a garden hose to the transfer tube and watch the adaptor plate, see the water passage?

Make sure this passage is clear, no chunks of a prior impeller restricting flow.

If the gasket fails here cooling water will drop straight into the exhaust and out the bottom.

I like to take a sharp punch and lightly tap a line or two across that area between the cooling water and exhaust. Do the same on the bottom of the powerhead. The 'dots' don't have to be hard, just enough to provide a slight 'tooth' so the gasket cannot slide. You do not want craters with sides raised so much they interfere with the surfaces coming together.

Interesting tip. I'll give it a try. So i'm just putting dimples in the aluminum to keep the gasket from sliding? No blocks in the water tube. The water tube slides out easily (no need to pull the power head, you can pull it out from underneath) and there are no blocks. I'm going to run vinegar through the block tonight to see if any salt build up or something came in here.


That pulsing leak under the ignition plate needs attention. it may be at the case parting line, hard to see.

Stick your finger in there, is that fuel? If so there is a definite fire hazard.

I believe it was fuel. The line was cracked and has since been replaced.

[Nevek]

So after cleaning all the gasket surfaces and flushing the motor with vinegar, I have made some discoveries.

1. You guys were right, water appears to just go into the mid section and not through the exhaust like I previously believed. This is evident after I back flushed the block and water came out of here:

http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/571fd2d0-bf11-4e2c-892f-5beb8ec95aa3_zpsdc8e6a5f.jpg

2. I filled the block with vinegar which uncovered these two holes. The one on the left MAY have been open previously and I didn't notice it right away, but it definitely cleaned up more once I got to it. The one on the right was sealed up and didn't open up until after cleaning. At first I thought these were holes from corrosion but the one on the left definitely looks machined so I THINK they are normal, and definitely better once opened up. Confirmation?

http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/c0766a3d-4880-4638-9892-31ca10758994_zpsaef53c79.jpg

So now that I know that water is supposed to be in the midsection (an not just in the exhaust tube like I previously thought). Is it possible that my only issue was these little holes were plugged up and my lower unit to midsection seal wasn't good enough? Can I put RTV or something on that to keep it from leaking out the side?

[muskamoot]

Some water is directed out the exhaust to keep the exhaust from over heating too.Those pooched gaskets as well as the plugged exhaust holes are probably 100% of your problem.The exhaust plate gaskets under the power head are vital to directing the water to the right places.All areas that can trap water in the motor are provided with drain holes,so water does appear to be coming from areas that you wouldn't normally think it should.Your motor has no poppet valve,so it is going to have to relieve the excess water from the pump somewhere,so don't seal up that side vent.

[Nevek]

Some water is directed out the exhaust to keep the exhaust from over heating too.Those pooched gaskets as well as the plugged exhaust holes are probably 100% of your problem.The exhaust plate gaskets under the power head are vital to directing the water to the right places.All areas that can trap water in the motor are provided with drain holes,so water does appear to be coming from areas that you wouldn't normally think it should.Your motor has no poppet valve,so it is going to have to relieve the excess water from the pump somewhere,so don't seal up that side vent.

What do you mean pooched gaskets?

Here is a picture of the two little coolant holes (to the right) flowing smoothly.

http://i50.photobucket.com/albums/f320/blueovalstanggt/2013/Mercury%2045/photo2_zpsa6ef5a42.jpg

[muskamoot]

Pooched as in baked,broken and wasted.In other words you need to buy 2 new gaskets and prepare for the sticker shock if you get Mercury parts,mine were $75 for the two.

[Nevek]

Already purchased, they are on their way and around $16 for both from Boats.net. I haven't really worked with outboards much so I wasn't sure if the gaskets were good or not. Hard to tell after you take the powerhead off and they rip apart. Good to know you think they too may have been part of the problem!

[Steve Pope]

Are the water intakes on the gearcase removable plastic screens. If so they may be fitted back to front which would cause a lack of flow when the boat speeds up. Stuck it on a mercruiser years ago. Could be as simple as that. Cheers Popey