1975 Mercury 7.5 progress report

[MassillonBuckeye]

Acquired a 1975 Mercury 7.5 with the thunderbolt ignition yesterday that was sitting probably 15+ years in his basement on a horse. Almost still has showroom shine! Am hoping for very little trouble getting her water ready and plan on impeller and checking out the carbs. Had an issue the rope mechanism wasn't engaging the flywheel.. Was planning on taking that assembly off and finding something stuck, but had trouble getting the screws out. Man them boys are in there.. So shot with WD-40 and went for my mallet.. Tapped it a couple times, then decided to tap the very top bolt a couple times and that housing.. Voila! Sometimes its something so simple... My first outboard and plan on running it on my 15'4 Gheenoe. If I didn't think the impeller was totally rotten, i'd be filling up the ole trash can for a start.. Wouldn't be surprised if that thing started right up just fine tho! Nice little engines..

 

[Capt'n Chris]

Re: Funny thing just happened..

Re: Funny thing just happened..

If the motor has been sitting that long unused, be wary of the seals. Dry seals will allow all sorts of damage. Your water jacket seal and prop seal should be of immediate focus. Change your lower unit lube and plug seals before running in water. After you have run it in water, check your lower unit lube for water intrusion. If your water jacket seals are bad, you'll know it in short order.

 

[Mi duckdown]

Re: Funny thing just happened..

Re: Funny thing just happened..

Sounds like a nice find, and perfect for that Gheenoe. First off is it short shaft?
1. remove spark plugs and squirt some light oil in while it is on the floor resting on the clamps, (plug holes up). Let it sit for a day. Than pull rope.

2. check compression before you go any further.
3 report back.
I know you are Geeked. One step at a time.
we are here for you.

 

[bob1340]

Re: Funny thing just happened..

Re: Funny thing just happened..

I just re-did a '69 or '70 model. I did reseal the bottom end for fun. This motor actually had very little use. The exhaust housing had no carbon build up on it. I did replace the water pump, rebuilt the carb and fuel pump and put new hoses on to replace the old dry hoses. I did the oil in the cylinders and would turn it over a little every day to make sure everything had lube on it. I put it in the tub, pumped the bulb, squirted a half a teaspoon or so of mix in the carb throat, choked it and it fired on the first pull. It did die as I didn't get the choke off fast enough, but first pull. Runs like a sewing machine. I hope to get the boat ready for water in the next couple weeks. I paid $175.00 for the boat and motor.

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

I just re-did a '69 or '70 model. I did reseal the bottom end for fun. This motor actually had very little use. The exhaust housing had no carbon build up on it. I did replace the water pump, rebuilt the carb and fuel pump and put new hoses on to replace the old dry hoses. I did the oil in the cylinders and would turn it over a little every day to make sure everything had lube on it. I put it in the tub, pumped the bulb, squirted a half a teaspoon or so of mix in the carb throat, choked it and it fired on the first pull. It did die as I didn't get the choke off fast enough, but first pull. Runs like a sewing machine. I hope to get the boat ready for water in the next couple weeks. I paid $175.00 for the boat and motor.

Yours sounds about like mine. Hoses aren't dry at all, checked the fuel filter screen which was just about perfect. I took some pictures of it, should I upload? This motor was probably used 15 times tops. I don't want to take the carb off if I don't have to. Marina here wanted $85 for a whole rebuild kit I'm assuming. Highly doubt it even needs it.. The cork gasket holding the fuel filter on looked like new. Why would it need rebuilt unless its gunked up? When you say "oil in the cylinders", what kind of oil are you talking about? Light-weight = 5w30? I appreciate the help fellas! One other question: how about the foam lining the cowl? Seems to have gotten brittle and is flaking off in a spot. Should I scrape it out? Don't want it getting all over everything if it starts falling apart. And the rubber piping on the under edge of the sides of the cowl have come off. Two part epoxy em back on?

I got a good deal on the Gheenoe and trailer. $500 out the door. '91 High Sider. She looks a little rough(oxidized olive green), but she sure fishes nice

 

[bob1340]

Re: Funny thing just happened..

Re: Funny thing just happened..

Try it like it is. When you change the water pump drain the oil from the gear case and see what condition it's in. The gear box takes 3.75 ozs is all.

The rubber pieces on the cowl are no available to my knowledge. Mine are bad as well. If you remove them the cover will fit loose on the cowl and possibly fall off or at least rattle. I'm thinking camper shell weather stripping will work.

Any oil in the cylinders would do. A squirt of 2 stroke oil is what I used.

 

[Mi duckdown]

Re: Funny thing just happened..

Re: Funny thing just happened..

If the compresion is good.
Remove lowerend and replace impellar, before trying to start it.
the last thing you want to happen is break off the fins and send them into head.
They become more brittle without use, and have already taken a set. 25 bucks for the part.
Good insurance.

 

[bob1340]

Re: Funny thing just happened..

Re: Funny thing just happened..

If the compresion is good.

I sure am no expert when it comes to outboard motors, but I don't think doing a compression test on a 2 stroke motor that ain't been fired up in years would be accurate. Make sure the rings are oiled well and run the motor for a while to make sure the rings get re-seated then check compression.

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

If the compresion is good.
Remove lowerend and replace impellar, before trying to start it.
the last thing you want to happen is break off the fins and send them into head.
They become more brittle without use, and have already taken a set. 25 bucks for the part.
Good insurance.

Yeah definitely doing the impeller tomorrow morning. Taking it to a marina here and have them check it out a bit. Will post results!

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

Try it like it is. When you change the water pump drain the oil from the gear case and see what condition it's in. The gear box takes 3.75 ozs is all.

The rubber pieces on the cowl are no available to my knowledge. Mine are bad as well. If you remove them the cover will fit loose on the cowl and possibly fall off or at least rattle. I'm thinking camper shell weather stripping will work.

Any oil in the cylinders would do. A squirt of 2 stroke oil is what I used.

I have the rubber pieces. They are fully intact it just looks like the glue got old and no longer held. They are real clean so I figured just epoxy them back on?

 

[Wingedwheel]

Re: Funny thing just happened..

Re: Funny thing just happened..

I have the rubber pieces. They are fully intact it just looks like the glue got old and no longer held. They are real clean so I figured just epoxy them back on?

Thats the nice thing about owning an outboard. Its yours and you can do whatever you want with it. If it works, your a genius. If you mess something up you share experiences with everyone on here. We learn from each others mistakes and victories.

 

[Mi duckdown]

Re: Funny thing just happened..

Re: Funny thing just happened..

RedWing I had to read that myself, like 5 times.
I hope he is talking about the Cowl rubber.???
And not the impellar blades.???

 

[Wingedwheel]

Re: Funny thing just happened..

Re: Funny thing just happened..

MIducky, he's talking about the cowling trim.

 

[RicMic]

Re: Funny thing just happened..

Re: Funny thing just happened..

I wouldn't use epoxy on the rubber seal, you'll never be able to get it off the cowling and it won't stick that well to the rubber. Use some "Barge" cement or automotive weatherstripping cement.

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

RedWing I had to read that myself, like 5 times.
I hope he is talking about the Cowl rubber.???
And not the impellar blades.???

Yeah a couple of the impeller blades broke off at the base and I just epoxied them back on. Works like a charm!!







































HAHA just kidding!! It would be the cowl trim im talking about. The longer side pieces. Ok barge cement eh? Don't know why I'd ever want to take em back off though. Adhesion would be the main concern. Also having issues with the foam pieces lining the inside of the cowl starting to flake. Dad recommended duct tape... The good news is she fired right up! Changed the lower unit oil, replaced impeller, inspected rest of water pump, looked good. Bought tank and new hose/fittings, hooked up em, primed, took about 5 pulls but the first 3 I had the choke on. Baby purrs. First start, no water from tattle-tale. Immediately shut down. Re-examined and realized I didn't seat the water tube right. I initially left it attached to the lower unit and just shoved everything back up in there. So second time, i pulled it from the water pump, installed it first to the motor, then mated the lower unit and inserted water tube into top of pump. Is there a trick to working those seals holding the intake tube and water tube on each end? They had these little circular tabs and were just about impossible to cram back into the holes.. I ended up just picking off those tabs so I could seat the tubes back in place.. Should I have lubed the impeller? Hands were all greasy anyhow so just left a slight coat of grease on everything in there. Lubed the spines of shifting link and driveshaft. The drive shaft was just slightly rusty at the bottom above the water pump housing/rubber ring seal. Does that mean leaking water pump? I was really surprised there was no gasket in the lower unit. Just mates up with 2 bolts/nuts. 1 in front, 1 in back near water intake. No gasket there makes me a bit nervous for the shifting link and driveshaft.. Sorry so many questions! Thanks for the replies!!!

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

Another update. Had it on the water for about 8 hours yesterday. Only issues were 1: Not planing. porpoising. But my weight isn't being distributed evenly. Fuel tank, Me(230#) and motor in the back, not much to note up front except a 15lb anchor so I expected this. Looking into a Hydrofoil of some sort. Like a Stringray Jr. Not too keen on drilling into the engine but.. This is going to be my setup for as long as I forsee. Running motor on bottom pin, and raising it a pin is only going to raise the bow more right?

2: Surging(or bogging not sure) at WOT. All through throttle range was real even until wide open. Not sure if it was trying to plane and doing that but I just backed off since it hadn't been run in a while. Going to check the plugs when I get home tonight. Do i need to prime it again after the initial prime? Hadn't really thought of that. Primed the bulb early afternoon in my garage and figure I was good. Maybe I wasn't getting enough fuel? Wasn't flooded that I know of, didn't smell gas. Was starting first pull EASY for the first few hours, until the last start of the night which took about 10-15.. Was starting to get nervous!

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

If the motor has been sitting that long unused, be wary of the seals. Dry seals will allow all sorts of damage. Your water jacket seal and prop seal should be of immediate focus. Change your lower unit lube and plug seals before running in water. After you have run it in water, check your lower unit lube for water intrusion. If your water jacket seals are bad, you'll know it in short order.

Any tips on these seals? I was breaking off the little notches to get em back in their housings... For esample, the water tube. I had to pull the tube And the seal out of its housing on the pump. Couldn't get the tube out of the seal without damaging it. They were still very supple though. Even the impeller

 

[bob1340]

Re: Funny thing just happened..

Re: Funny thing just happened..

I am interested in these seals as well/ Are we talking about the rubber tube seals that go in the water pump and block on either end of the water tube? Are you referring to the baffle gaskets? I don't have a factory manual yet so I am just looking at part diagrams. What is the water jacket seal?

 

[MassillonBuckeye]

Re: Funny thing just happened..

Re: Funny thing just happened..

I am interested in these seals as well/ Are we talking about the rubber tube seals that go in the water pump and block on either end of the water tube? Are you referring to the baffle gaskets? I don't have a factory manual yet so I am just looking at part diagrams. What is the water jacket seal?

Yes. There is also a seal on the intake grate. So one end of the intake tube goes into that and another on the water pump. Then another on the Top of the water pump which holds the long part of the water tube which sends water up to the motor. Those seals. Whats the purpose of the rubber "oil seal" that just sits on the top of the water pump around the drive shaft? THere isn't even any oil in that part of the lower unit...

 

[Mi duckdown]

Re: 1975 Mercury 7.5 progress report

The lower end is self contained