1988 70HP Mercury Lower Unit

[bwhalerman]

The alarm sounded somewhat like the home smoke detector (not as loud but constant like that).Since I have no oil tank on it and mix with gas I knew it couldn't be the oil sensor as that is probably disabled. Once several weeks ago I heard a very brief chirp and then it never came back. Then just before I decided to put in a new impeller and gaskets it sounded like a horn.

Today was a new experience. It sound very shrill and when I went back to the motor that is when I recognized the starter was spinning very fast. It did drop back down after turning the flywheel and starting the motor but it continued to spin. So, I am a bit confused. The power head was fairly hot so I assumed it was the thermostat and then I saw the head of the starter spinning and didn't quite sort out what caused the loud horn like noise I heard. Could it have been both the horn and the starter. Tomorrow will tell.

Tomorrow I'll check the solenoid (installed a new one last season) and I'll replace the thermostat and popplet valve. As you noted these are good change outs anyway with an older motor.

The good news is that I can now probably change a prop shaft and all components while holding a cold one in one hand. It worked out perfectly. You have been an extremely good help and I want you to know that I am grateful for your help.

 

[Texasmark]

Thanks for the compliment. I enjoyed it. If you changed your solenoid last year then it's internal contacts welding shouldn't be the problem.
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"................. when I went back to the motor that is when I recognized the starter was spinning very fast. It did drop back down after turning the flywheel and starting the motor but it continued to spin."


"...when I went back to the motor that is when I recognized the starter was spinning very fast."......................... What happened prior to your hearing the squeal and your going back to the motor? Did you just start the engine? Had it been running for a time while you were checking out the items you mentioned were working, shifter and all? Had it run long enough to get warmed up? The temperature where the stat opens is right at where a US domestic hot water heaters operate when temperature is set on NORMAL for a reference as to how hot is ok on the engine and shouldn't produce an OT condition.
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" It did drop back down after turning the flywheel and starting the motor but it continued to spin."

I don't understand this. What is the timing of this event vs my questions above?

Are you telling me that the starter is spinning without the engine running, key off? When did the squeal start? What were you doing? I assume the squeal you heard was the spinning starter. If you started the engine and the starter stayed engaged, that is what I thought was happening.

The Bendix could be stuck due to lack of lube on the shaft.

The Starter could be energized because the ignition switch is bad and feeding energizing voltage to it in the IGN. OFF or ON positions.

 

[bwhalerman]

What happened prior to your hearing the squeal and your going back to the motor? Did you just start the engine? Had it been running for a time while you were checking out the items you mentioned were working, shifter and all? Had it run long enough to get warmed up? The temperature where the stat opens is right at where a US domestic hot water heaters operate when temperature is set on NORMAL for a reference as to how hot is ok on the engine and shouldn't produce an OT condition.

Good questions. The first unrelated thing I did after installing the lower unit was to shift FNR to make sure that was working. Not a problem there, everything worked as it should.

I started the motor a couple times to do the initial carb adjustments and was then going to take it down to the river to refine the adjustments. It sputtered and stalled a few times and finally started long enough to do some preliminary adjusting. In between each start attempt I waited about 20 seconds or so to try again. Didn't want to overheat the starter. I would say the motor ran for about 3-4 minutes with hose connection. It was at this time the horn emitted a steady very audible noise as the cowling was off both sides of the motor. I turned the key to the off position, stopped the motor. It was at this time I got a bit confused as to why the noise continued. I reconfirmed that my key was off. I quickly got out of the boat to further examine the noise and notice that the bendix had dropped back into the normal resting position but the head of it was spinning so fast you could barely see the teeth. My next step as to disconnect the battery.

I too was thinking it may be the ignition switch at the helm as it did turn within the nut set that is supposed to secure it to the console. I guess a number of things happening at one time was a bit confusing to take in because I wasn't in position to spend much time on it today and when this problem occurred it took me by surprise. But, as I thought about it more today I was considering two things. The first is the bendix may need lubrication and secondly it may be the ignition switch.

I think my initial assessment several weeks ago when the horn sounded was thermostat. And when I went in that direction also decided I would replace the poppet valve as the horn sounded after I was running over 2 k for about 5 minutes.

 

[Texasmark]

The loose nut on the key switch is a nuisance I too have endured. But a sealer around it, like RTV could help. I just never bothered....just snugged up the nut, usually with my fingers....were handy at the time. Grin

I think your next move is as you say to get the stat and popoff changed. Surely you will inspect them when out and look for a smoking gun. The stat will show it's colors in a pan of water on the stove......the opening temp is stamped on the bottom of the copper pellet. A piece of string wedged in the opening area with the stat suspended in a pot of water going to the boiling point on the stove will show itself when it falls to the bottom....a candy thermometer is what I use for the temp. reference. The popoff should unseat at (swag) 10 psi of pressure which you could exert with your finger for a "see how it works" test of that.

On the starter, it sounds like the key switch. The small terminals on the starter solenoid are internally attached to a coil of wire. Current from the ignition switch runs through those contacts producing magnetic induction which sucks in the steel rod to which the copper "switching" disc is attached. This disc slams across the two ⅜" copper studs and makes a complete circuit sending your starting amperage to the starter. The only way your starter can keep running is the switch is thus closed. Question is how:

Discount welding shut due to replacement a year ago.....life expectancy, 10+ years, depends on number and length of starts.

Starter switch, 1988, lots of starts and stops, builds up metal filings internally, metal filings migrate over to other contacts making connection when they aren't supposed to be connections. Other thing, switches are usually made from Phenolic, which is a carbolic acid saturated cardboard used for electronic circuits for 10's of years...before fiberglass. One of it's drawbacks is that it absorbs moisture which supports terminals shorting out.

Have to grin when I think of your original comment " I usually work 12 hours a day, but I have reserved 6 hours on Saturday to work on my boat". Yeah right. Like me, you get into something and you want to see it through. Hope your business didn't suffer. Grin.

 

[bwhalerman]

I'll post back after I check the thermostat and popplet. Definitely going to replace the ignition switch. This is beginning to sound like the Johnny Cash song about stealing GM parts and building the car. After all of these small issues are cleared up I'm hoping I'm back on the water because the cost of repair is mounting.

Yeah, I did spend a bit more time than expected. It did cut into the work I usually do on weekends but as a small biz guy it's necessary to be flexible to change and disciplined about the fundamentals. So, I mark the Saturday outboard repair to the flexibility side of the equation.

 

[Texasmark]

I'll post back after I check the thermostat and popplet. Definitely going to replace the ignition switch. This is beginning to sound like the Johnny Cash song about stealing GM parts and building the car. After all of these small issues are cleared up I'm hoping I'm back on the water because the cost of repair is mounting.

Yeah, I did spend a bit more time than expected. It did cut into the work I usually do on weekends but as a small biz guy it's necessary to be flexible to change and disciplined about the fundamentals. So, I mark the Saturday outboard repair to the flexibility side of the equation.

Well sir "beins" you're the boss, you set the rules. Grin

Bright side....get all this fixed and it's gone for a few years. Result is enjoyable boating. This will soon be a distant memory.

 

[bwhalerman]

No Title

A person with NO mechanical skill would know this is the original thermostat on a 1988 motor. The paint on the bolts was never cracked. Unfortunately 2 bolts snap. Tried WD40, soaked them...some came out okay but 2 surrendered. The poppet valve no doubt is the original. Both are going to go.

 

[Texasmark]

Yikes.....yes it needs to go. On SS into Alum + marine environment + age, one has to expect problems like snapping bolts. I like to crack/scratch off the paint to aid in penetrating oil penetrating around the bolt head and hopefully down into the threads. PB Blaster is a quality penetrating oil widely available around here. I like to let it sit overnight.

Impact type torque has proven itself to me time and time again, in old farm equipment, marine engines, and OTR vehicles. For something like a ? -5/16 bolts you find around the water jackets and all, I improvise by using a boxed end wrench and a 1 lb hammer (not too big, not too small). Grasping the wrench back from the end and applying forward pressure against the bolt, I smack it lightly (repeatedly) and then more intensely. Cannot remember the last time I broke on.

One of the mechanic guys on here suggested grinding the heads off, removing the cover and since the threads are now exposed (somewhat) apply your oil there and wait overnight. Then vise grips and the smack.

Moving right along.....another smoking gun put to rest.

 

[bwhalerman]

the bolts were backing out with some resistance and the two that snapped were coming along just fine. And then one turn, snap! Like we noted earlier many of these things definitely need attention. Over the winter I may continue on and pull the cover to the exhaust and check that out. But for now I'm involved in a trip to the beach for the weekend and the following week another all day event on Saturday so I have some time to poke along. Crabbing hasn't been all that great anyway. Just want to get underway for the big ones in October and the Rockfish run.

 

[Texasmark]

How about the thermostat?

I grew up on the Texas Gulf Coast. Galveston and Rockport (near Corpus Christi) is where we fished for the Blue Crab. Had to fish at the end of the full moon for the pincers to be full. Boy did I love them boiled with a tad of Worchestershire.

In Galveston we strung the main horizontal lines along the beach tied to posts driven in the surf and ran lines off the main line baited with chicken parts. Water was muddy and rough. Waded out with a dip net and #10 wash tub.

In Rockport we'd go out in the bay, maybe half a mile from shore and wade in the clear water, dragging a skiff behind and scoop them up with dip nets. I was a kid then and at Grandpaws and I had a blast every summer. His boat was a 16' flat bottom, planked skiff with a 10 hp Johnson...the one with the slide throttle, 360 degree reverse and fuel tank filler on top of the cowl......real neat outboard design. That's just what you need.....trying to fish and keep the bait tantalizing just to have to get out the gas can and reach back over the motor, with the boat pitching up and down, and fill the gas tank, getting gas all over everything in the process. Wow have things changed.

 

[bwhalerman]

Well, it's time to call in the pro's. The summer is slipping away and it's time to get back on the water. The bolts that snapped made it nearly impossible to use an extractor on them. There isn't a good enough flat surface to get the extractor started. On top of that the carrier inside the pop valve is so fused to the jacket it will need to have heat applied to set it free. No doubt preventative maintenance was not too important. I got a lot of things done and then with your help got the gear case back in order and nary a curse word was uttered that to me is truly a great achievement. I'm heading to Ocean City Maryland for a long weekend vacation and have another event the weekend of the 10th so I couldn't get to it until another couple weeks. I don't want to wait that long so off to the shop tomorrow to finish my punch list.

I understand you have satisfaction helping others with motor issues but you have truly gone above and beyond what anyone could have ever expected. I am very grateful for your time and what you have taught me. I'll let you know how it all turns out.

Hope you have clear skies and calm seas.

 

[Texasmark]

You too. Enjoy your vacation.

 

[bwhalerman]

A final note about my recent experience and some things I learned that others may profit from.

When my shift shaft pulled out of the shift tube while pulling the lower unit the cam that the end of the shaft mates with at the bottom of the tube slid forward. That means towards the front of the gear housing. Some people suggested tilting the lower unit to get it back into place it didn't work. I ended up removing the prop shaft to retrieve it. Here is a trick I would use today if it were to happen again. Slide a long non-metallic item, maybe a piece of cardboard, down the tube to block the opening that is seen in the area facing the prop shaft. Next insert a long flexible magnet into the tube and snake it toward the front of the gear case. This simple trick should snag the cam and you can then pull it back into the center of the tube and insert the shift shaft into it.

The most important thing I know and was reminded of; and it's something we all know intuitively, is if it feels like you shouldn't be doing what you are about to do...don't do it. Next, get on this forum and ask some questions. I was removing my thermostat and poppet valve from my motor as it overheated. I knew it had to be the thermostat as the motor is a 1988 and I could see that the cover has never been removed. The original paint was not cracked. I unscrewed the first 3 bolts while applying lubricant. The did come out but with a little too much resistance. The remaining 2 were similarly difficult but this time they broke. I should have stopped and ask for lubricant suggestions. You see where I'm going. If you have some basic skill and dig into your motor and confront something that doesn't seem right, STOP and guys on this site can make your life a whole lot easier.

 

[Texasmark]

A final note about my recent experience and some things I learned that others may profit from.

When my shift shaft pulled out of the shift tube while pulling the lower unit the cam that the end of the shaft mates with at the bottom of the tube slid forward. That means towards the front of the gear housing. Some people suggested tilting the lower unit to get it back into place it didn't work. I ended up removing the prop shaft to retrieve it. Here is a trick I would use today if it were to happen again. Slide a long non-metallic item, maybe a piece of cardboard, down the tube to block the opening that is seen in the area facing the prop shaft. Next insert a long flexible magnet into the tube and snake it toward the front of the gear case. This simple trick should snag the cam and you can then pull it back into the center of the tube and insert the shift shaft into it.

The most important thing I know and was reminded of; and it's something we all know intuitively, is if it feels like you shouldn't be doing what you are about to do...don't do it. Next, get on this forum and ask some questions. I was removing my thermostat and poppet valve from my motor as it overheated. I knew it had to be the thermostat as the motor is a 1988 and I could see that the cover has never been removed. The original paint was not cracked. I unscrewed the first 3 bolts while applying lubricant. The did come out but with a little too much resistance. The remaining 2 were similarly difficult but this time they broke. I should have stopped and ask for lubricant suggestions. You see where I'm going. If you have some basic skill and dig into your motor and confront something that doesn't seem right, STOP and guys on this site can make your life a whole lot easier.

That's some good info. Mr. B. On the cam, if people knew to hold onto it while separating it'd help, be nice to have an access point without having to tear things apart, be nice to be able to see down in there.......

Twisting off bolts is a serious issue the older engines get especially used in salt water. If the OEMs would use blue thread locker it would go a long way to prevent breakage.......helps to insulate the dissimilar metals from each other, besides resisting vibrating out which is not really a problem of which I am aware. I used it for years in industry and it does what it says it will do.

 

[bwhalerman]

Well Ed looks like the saga continues. The mechanic called and let me know 3 things that turned the smile upside down for a few moments. He said they had to remove the water jacket cover to get the the broken bolts holding the thermostat cover. Needed to do extensive work to remove them and put in new bolts. I also asked they synch the carbs as I had rebuilt all three. When I was attempting adjustment at home all three responded to adjustment but when they tried a the shop he said the top carb didn't respond. It could be that the float is stuck. He also found oil leaking from the weep hole. Thinks it could be the shift shaft seal. I did replace the O ring under the shift shaft cap. The external small O ring looked fine so not sure what's up.

At this point we're at 14 hours labor for which he said he will charge 10. To finish up may be another $300.00 bringing the total nearly $1,500. I said stop. My wife said go, let them finish it. What do you think?