88 johnson 6 hp tell tail weak, and hotter then it should be

[relics hunter]

What's with the water problems, It seems like a outboard water gods have something out for me. My 35 hp had bad water deflectors and then a bad exhaust gasket all the advise I got on that was great and it's running great. The 6hp had been running good for months getting some good fishing in and then the last time out It acted weak on the last short distance to the dock. It wouldn't get up and go, and when I ran it to clean it out after getting home the tell tail seemed weak, and noticeably hot. I ran some vinegar through it and checked for clogged intake. I pulled the foot and looked over the impeller, which is maybe 6 months old. I happened to have another new one and swapped it out. Put the foot back on and ran it, still a weak stream, and hot, and I turned it off when the temps got to high. I pulled the thermostat cover off and cleaned and tested the thermostat. I did find that the previous owner decided to use silicone sealant instead of a gasket, and perhaps there are fragments of sealant deeper in the motor. I cleaned all I could reach and reassembled with a gasket. My understanding is the water comes to the tell tail just after entering the upper motor, and then passes through the thermostat and on around the cylinders and such. Thermostat tested good. So for the water in the tell tail to get quite warm/hot it seems to not be moving along like it needs to. I am getting water and exhaust spitting out the back port. One of the symptoms of the blown exhaust gasket on the 35 was no water with the exhaust. It doesn't look like the 6hp has water deflectors. I did feel a little temp change as the thermostat opens and closes, so I believe it is working. I am thinking I have to tear into it and find some scrap of silicon that a nit wit added to the system.
What do you think?

 

[oldboat1]

Before taking it apart, you might first try flushing from the top -- remove the t.stat and cover, and flush through the t.stat opening.

 

[Vic.S]

If the pump is OK but the pee stream weak Id look at the grommet at the top of the water tube

( If the pee stream was strong but motor overheating I take the cylinder head off and check/ clean the water channels in it.)

I have an '84 6hp, The top grommet is a PITA Corrosion of the alloy inner exhaust tube squeezes the grommet over the end of the tube until it stops the water flow,
You can tell by poking a stout wire up the tube when the gear case is off. It it hits something rubbery at the top thats it. If you cannot feel anything rubbery then probably OK

Power head off to replace it!

The outboards equivalent of an enlarged prostate

 

[oldboat1]

agree with Vic's post. For salt corrosion, normally have to get in to the water passages. Take care with the head bolts.

But would try some flushing first (How did you do the vinegar flush?) If the l.u. is off, as in Vic's test for the bad prostate, you might try flushing from under there too (from the bottom and down from the t.stat opening). Have to rig a fuel hose or similar to fit over the water tube, not too much pressure whether using a pump or hose.

 

[relics hunter]

I flushed from the bottom with a small size hose and water freely came out in all three places. I would think that rules out the grommet being bad. When I had the thermostat off I pumped in vinegar with a squeeze bottle. I am just not sure, I keep leaning toward foreign object.

 

[oldboat1]

Might be right, although if water is circulating from the bottom out the tell tale, through the head, out the leg and exhaust port, seems like any blockage was cleared. Think I would do a compression check, make sure the bypass in the t.stat housing is clear. If no issues, would try it again in a barrel or in the lake. If still overheating, would pull the head. You might have a leaking head gasket or some stubborn corrosion -- or a piece of that sealant in tight (or piece of an old impeller).

 

[relics hunter]

Can anyone give me the compression spec for this motor, 1988 6hp johnson.

 

[ondarvr]

There is no spec, but they are normally low, from maybe 65 up to 95 psi. This can vary a great deal depending on the gauge though.

Could be a head gasket, the pee stream should be cool at all times, it doesn't go through entire cooling system.

 

[raczekp1]

i had one 6 hp motor made in 1987 with compression 130 psi each cylinder

 

[tommarvin]

Have you used an IR thermometer to test temp just to be sure it's overheating. What temp did the t- stat open?

 

[relics hunter]

I checked the compression and I got 110 and 105 on them.
The thermostat was opening at about 140, it was hard to get an exact temp with a temp gun, and the block raised up to 190 when I was running it after replacing the impeller. This problem had just started on the way back to the ramp, I couldn't get a full throttle up, and then testing at home noticed the temp of the tell tail, and weak water flow from there and exhaust. It's just stumping me. I pulled the exhaust cover and found a part of the gasket was out of place, but it's been that way a long time( you can see impressions of it on the plate), and it's not blocking anything. I will dig deeper in cleaning out passages. The tell tail being hot leads me to look from there back.

 

[tommarvin]

Our T-stat opens at 110F, and our overheat buzzer goes off at 180F when you test a t-stat you take it out,put it in a pan of cold water slowly heat it up what temp does it open? You don't know on the motor.

If you can remove the cover screens on LU water intake to look inside for blockage, old impeller fins, garbage, plastic.

Looking down on impeller, drive shaft turns clockwise, are the fin oriented for a clockwise driveshaft turn? did you put the keyway back in on the drive shaft?You said weak water flow.

If the impeller, t-stat 110f, sensor is ok,nothing is blocking the intake,the block should never get to 180f you said 190f.

It's time to remove cylinder head , find problem,order a head gasket,get a inch pound torque wrench at hf tools find torque sequence and inch pounds at each torque sequence.

 

[relics hunter]

I had tested the thermostat in a pot of water. It took some searching but I found a part supplier that actually listed the thermostat as 143 degree. I will pull it and test again. I wanted to see if I can flush any more crud out anyway. The screen on the foot is in good shape and permanently attached. I have a head gasket coming and I'll just open and clean everything I can get to, and see what I get after reassembling.

 

[oldboat1]

The t.stat should start to open at the rated temp. You want to be sure it fully opens (not sticking). You can't get a water temp with an IR gun -- will read the surface temp of the container bottom. That may be close enough for your purposes, but I would dunk the thermostat in hot water (something around the overheated temp you engine was running or thereabouts). It should be fully open at 160. If in doubt, I would replace it. Assembly is important too, btw. Yours might have a slotted rubber gasket fits around the flange/rim of the t.stat body.

 

[relics hunter]

Well I replaced the powerhead gasket and the t.stat with no cure for this issue, so my next best guess is the exhaust housing gasket. Is it possible this gasket can cause this? I did notice it seems to be only over heating on the upper cylinder with a tempgun.

 

[Vic.S]

Well I replaced the powerhead gasket and the t.stat with no cure for this issue, so my next best guess is the exhaust housing gasket. Is it possible this gasket can cause this? I did notice it seems to be only over heating on the upper cylinder with a tempgun.

Maybe when you take the exhaust cover off you will find a blockage

 

[relics hunter]

Maybe when you take the exhaust cover off you will find a blockage

the exhaust cover was the first place I looked and found no blockages. I'm thinking the exhaust gasket under the powerhead to the midsection.

 

[tommarvin]

When you find the problem, please tell us what it was, so I can learn something. Just to be clear, new stat that opens around 110f . 140F seems to hot. If it has a very small slot that is the top at 12 o'clock. Can't open Water inlet port on LU to look for blockage. I just thought of something, remove lower unit check water inlet tube for blockage, push something up the tube and, pour water fast in the t-stat opening if this fixes it please thank the Force Forum, does it easily drain out the water tube. Your sure impeller is installed correctly with the keyway, fins oriented for clockwise drive shaft, you took the head off didn't snap a blot, all clean inside, water indicator stream starts streaming in 5-10 seconds strong, I'm at a loss for words.

The water tube is partly blocked. Free factory outboard service manuals at www boatinfo.no/lib/library.html Click the make, find your motor.

 

[Vic.S]

the exhaust cover was the first place I looked and found no blockages. I'm thinking the exhaust gasket under the powerhead to the midsection.

Sorry misunderstood which one.
Maybe that gasket has gone or maybe when you get there you'll find a blockage

I am puzzled by the fact you get a good flow hose a hose connected to the water tube but not when you run it.

Check that top water tube grommet while have the power head separated from the exhaust housing.

 

[oldboat1]

the thermostat starts to open at its rated temperature. It should be fully open within 15 to 20 degrees of its rated temp. Operating temps are normally measured at the top of the head, and between 140 and 160F is considered normal -- temperatures around the plugs will be higher.