TOPIC: 1970 1350 Lower Unit Removal: Help

Any input would be greatly appreciated. I want to inspect the impeller on my outboard. I had a few inline 6 outboards growing up that I did maintenance on but that was about 30 years ago. What’s the correct procedure for removing the lower unit on a 1970 Merc 1350? Should the engine be in gear? Besides the bolt under the zinc is there anything hidden that I’m missing? Any YouTube channels anyone can recommend to guide me? I really don’t want to screw anything up by forgetting a step. This is a great running motor and I want to keep it that way. Thanks in advance
Chris.

Hi, Chris, a nut on either side, one in the front up on top, one underneath, one under the trim tab as you mentioned, and of course the bolt from top for the trim tab itself.

Shine a flashlight down upon the trim tab's bolt head, some are 12-point heads but more likely it'll be a hex-headed bolt. If you're in a salty area and you have any stuck hardware, don't force it. Use a Propane or MAPP torch to heat the surrounding area. It'll help break the stuck parts free.

If the lower unit doesn't want to come down readily, don't pry with screwdrivers. It'll break the housing. Use wooden, metal, or plastic wedges at strategic points. If there's any salt buildup around the mounting studs, heat will help loosen that as well.

You can leave the shift in forward, it's usually the easiest. When you go to push the lower unit up, you can turn the prop slightly in the Reverse direction to get the driveshaft to turn and align its splines with the crankshaft splines. Goes without saying that you should disconnect the battery before start this work.

Use caution once the lower unit is off, to not move the shift shaft/cam from their current position. Nor move the remote control lever. Might not be a bad idea to take a picture or mark the position of the shift cam/shaft so if they get disturbed, you can realign them.

Use a good coating of water-resistant grease on all studs, etc. Use grease on the driveshaft splines but not on top of the shaft. Replace the driveshaft O-ring if your driveshaft has an O-ring groove below the splines.

Mercury Anti-Corrosion grease is very sticky and does a great job of keeping salt and other debris out of hardware. It works very well for lubricating the driveshaft splines, too. Failing that, I've used Sta-Lube blue boat bearing grease on hundreds of motors and never had an issue with it. Things always come back apart again with little fuss or muss.

When you're reinstalling, make sure you have the plastic water tube guide installed in the top of the pump, and the guide 'catches' the water tube as you're installing the L/U. A dab of grease on the bottom sides of the copper water tube helps the tube engage the rubber pump cover grommet easily.

The driveshaft engages with the crankshaft next. This is when you turn the prop just a bit to get the driveshaft splines to go up into the bottom of the crankshaft. After that, the shift shaft engages with the shift rod. That's usually the tricky one. If it just doesn't want to go, you can try wiggling the exposed portion of the upper shift rod as you're pushing up on the L/U.

In some cases there's too much preload on the shift cable, and it'll have to be undone from the motor so you can move the upper shift rod a bit to get it aligned with the shift shaft. Sometimes they go right in real slick, other times it's a bit of a fight.

Video-wise, this guy has some pretty good vids on a 115 Merc Inline Six, it'll be the identical process for your 1350:







If you sort this user's channel by oldest 1st, you'll find a ton of Inline Six vids as he rebuilds and completely goes thru his Merc. Very informative.

The 1350 is a Beast! Back in the 80's I had a Sidewinder 16SS (15'-9") ski boat with a 1350 that I put together myself. Picked up the powerhead with a busted crankshaft, and rebuilt it using an older 125hp crankshaft from a parts engine. It was a screamer on that boat! Back then we didn't worry too much about how much gas our outboards used, gas was cheap! I couldn't now afford the gas to go out to the lake 4 or more times a week, as we used to do when we were young and strong! But sure was fun while it lasted!

Hope that helps get you back on the water. If there are any questions you have at all during your L/U R&R process, be sure to post. We've seen it all!

Cheers..........ed

Wow, thanks a ton!!! Exactly what I was looking for. Glad I posted. Growing up my father had a ‘72 Aquasport Seahunter with a pair of 115 mercs. Unfortunately that boat caught on fire in a bad thunderstorm, we were able to salvage one of the engines and that went on a 19’ sea ray that my brother and I shared as our first boat. I was about 13 at the time. A buddy of mine had a later model 115 inline on his 16’ Baja. Boy I remember flying up and down the bay in that. That’s where we started learning to turn wrenches. Fast forward 30 years. I picked up a 1960 Bell Boy with the 135 on it. Hearing this engine run and the smell of the 2 stroke I feel like I’m a teenager again every time I’m on the water. This motor is a cream puff, it’s spent all but the last 2 or 3 years in fresh water so I don’t anticipate it to be too much trouble coming apart. From what I’ve been told it has less than 100 hours on it since last complete overhaul. I do just about all my own maintenance, but it’s been at least 25 years since I’ve pulled a lower unit on one of these inlines. It was pumping good water last season so I mostly want to inspect it. Last thing I want to do is damage this engine because I was too lazy to inspect and or replace something as simple as a water pump. Thank you again. I am a newbie here and glad I joined. I’ve learned a lot from the short time I’ve been here.

That's purty! Brings back fond memories. I had power trim 'n tilt on mine, it sure was nice for skiing and blasting down the lake. A stainless prop would improve the performance of your Merc quite a bit I bet. Of course you're pushing a much heavier hull than a ski boat.

Does this setup have a tach? These old Mercs like to wind out, and underway at full throttle, with just one person aboard, you should see somewhere in the range of 5300-5500 rpm. Otherwise, the engine is overpropped. Don't worry about hurting the powerhead by revving up that much, my 1350 saw upwards of 6000 rpm with no ill effect. Old Inlines like to rev!

Your Merc has a good charging system with a rectifier, so any modern 12V marine tach should work. The tach pulse comes off either of the yellow wires connected to the rectifier. If your remote control box has a tach connection on it, it's easy to do the wiring from there.

But with that flat-bottom hull, it should plane-out like crazy!

BTW nice kicker motor, too!!

Yes it does have a tach, but I need to figure out how the wiring was run, or what was altered by the previous owners mechanic. The previous owner had a cell phone and a Rolodex in his toolbox. I am just the 3rd owner of the boat. The original owner had it in his family since new, repowered it with the 135 for skiing, it originally had an 80 Merc on it. The previous owner had the key brake off in the original MercControl shifter and had their local mechanic replace the whole thing with a newer model. He did however save the original and pass it along to me. Eventually I would like to fix it and put it back on. I’m not sure if that has anything to do with it but I have some wiring to figure out. The lights on the gauges and fuel gauges work but the tach does not. All the courtesy lights on the dash and switches work but the running lights, FF/Depth finder VHF, CD/Stereo and cabin heater do not. For the most part, where I do my boating all I really need is a compass and my cell phone. I’m always within range, have a boat US policy and the app in my phone. From what I have been told the boat will run in the 40s and she really does hop right up on plane, but I believe the hub has spun on the prop as the last two times out I have felt some slippage. If the bronze prop can’t be fixed it will become a decoration in my garage and I will most likely just get an aluminum. For this type of boat I just can’t justify the cost of a stainless prop. Now if I ever run across an old Hudrostream to put this motor on, then the tilt/trim midsection will be added with a stainless prop

Boat wiring is one of my least favorite tasks! You never know what the previous owner has done to it. Sometimes it's better to start from scratch.

That hull in the 40's is a pretty good turn of speed, especially on that ancient bronze prop. BTW those heavy props are pretty rough on the gearbox. Once you get the tach working, you'll know your WOT rpm and whether the pitch on that prop is good.

You should see the pitch stamped on the body of the prop, and it's normally the last set of characters, for example a prop with 19" would have " -19 ", so on so forth. If you can still make out the part numbers, we can look it up in the old Merc propeller guide and figure out the diameter (which will likely be around 13").

A modern 3-bladed aluminum prop with a cup would be an excellent replacement. With a cupped prop, vs. a non-cupped prop (as is your bronze prop), you can go down 2" in pitch for better hole shot, and the cup will reduce rpm (rule of thumb, around 200 rpm less than the same-pitch non-cupped prop) at the top end. Best of both worlds.

It's certainly possible the rubber hub is slipping and I agree that it's not worth the $$$ to get the bronze prop re-hubbed, unless there's a specific need for a full-blown restoration. The new props are much more efficient.

Also a possibility that you're getting ventilation on takeoff, which could come from the characteristics of the hull and/or transom height of the engine. You can make a match-mark on the prop body with a Sharpie or a center punch, and a corresponding mark on the end of the propshaft. If those marks move in relation to each other after running the boat out on the water, the rubber hub is definitely slipping.

And tell ya what, that 1350 on a performance hull such as a Hydrostream will really Scream! My 15SS would go over 50 with a 'hot' stainless prop, but the vee-hull wanted to chine walk. So pretty scary.

A Mod VP or tunnel hull boat would have an excellent top end, with better high-speed handling. A vee-hull with a properly-designed pad at the stern would do well, too.

I haven’t given the prop a close inspection to look for a number. The original owner listed a 15* and 17* prop in his listing but I only received the one that’s on the engine now so I assume it’s one of the two. I don’t think the prop is cavitating, The prop shaft is well below the bottom of the boat so I don’t think the engine is too high, but I haven’t marked the prop so I can’t say for sure. I do have some experience messing with props and engine heights. My other boat is a 1985 Bullet 130(13’). I have it rigged with a ‘92 60 Merc mounted to a CMC manual jackplate. For cruising I lower the engine and run a 17* aluminum but I when I want to scream I have a Mercury racing solid hub 18* chopper. The boat has a pad on the bottom but can get pretty squirrely when trimmed out if I’m not careful

Looks like a lot of fun! The 60hp would be a Fuel Mizer compared to the Very Thirsty 1350!!

I have a 50hp triple sitting in the shop, in the middle of a re-ring/refurb. The bores were perfect but the rings were all carboned up. Had it miked & honed, new rings and a new bottom ball bearing. Now I just have to get off my duff and get the powerhead all back together and mounted. These are pretty light motors and make good powerplants for a smaller boat. It even has PT&T, even better.

It sure is, and with the aluminum prop it will stay on plane at 2200 rpm and cruise nice at 3000, with the chopper not as much, needs to run about 3400 to stay on plane.
Do you think the CMC tilt and trim units that are rated for 130hp would be ok to use on the Bell Boy? I know it’s 5hp over the rating but I see in the videos you posted he has one on his sidewinder(115), and they would be nearly identical weight. Also this boat isn’t beat up at all, just like a Sunday driver. It certainly would be much easier to get one of those than to swap out the midsection for a conversion.