1964 Mercury 39 lower unit stuck

[NWVintage]

Ok, I'm sure there's a thread about this out there, but I can't seem to find it.

I just got a 1964 Merc 39 that I'm going to use for a kicker. It runs great, which is awesome, considering I traded it for a 2wd Toyota fender...

I'm trying to get the lower unit off to replace the impeller, but it won't come the whole way off. I have the manual and have gone over the simple process several times to make sure that I'm not missing anything. It will drop about 2 inches, but gets stuck there. It moves fairly freely in and out over that 2-inch range. It seems that the driveshaft is catching on something at the powerhead end (when pulling, you can hear the light thud of it catching when you listen next to the powerhead). I had a similar problem with my 1963 850 but a couple good tugs took care of it (it was a bit rusty at the powerhead end). Does anyone have any ideas how I might loosen it, short of taking off the powerhead?

Any ideas would be much appreciated.

 

[sutor623]

Re: 1964 Mercury 39 lower unit stuck

A lot of motors have a small screw that you can barely see, on the shift linkage rod. When you start to drop the motor it will get hung up. Just unscrew it enough to slip the linkage apart and VOILA, shell slide right out.

If your driveshaft were stuck in the powerhead, the only thing that I have heard to do is to flip the motor over, spray PB Blaster right down the driveshaft, and let it seep into the powerhead splines overnight. Give those two a whirl and I'll bet ya you'll have that unit off tomorrow night after work......

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

Sorry it has taken a couple days to respond. Holidays and all...

Thanks for the ideas. This motor has a small square-head bolt that goes in at an angle to a metal bushing around the shift shaft. I suppose that this might be what you are talking about. I tried to loosen it but (I appear to have exaggerated the amount that the lower unit was dropping before - more like 3/4 inch) I couldn't get it with any of my tools (standard wrench too wide, needle-nose not enough grip). So, to get started, I turned it over and sprayed so PB down the drive shaft and I'm going to try to find a wrench that's super narrow (I had a few at one point that were essentially made out of 1/4 in hardened steel). I'll let you know the outcome.

If anyone has any specific knowledge of the Merc 39, your input would be greatly appreciated.

 

[Chinewalker]

Re: 1964 Mercury 39 lower unit stuck

DO NOT loosen that small square head bolt! It'll let you pull the shift shaft out of the lower unit, which you DO NOT want to do. The shift shaft is a spline fit and is not mechanically fastened to the upper end. It MAY have rusted in place if a previous servicing did not grease the splines prior to reassembly.

If you have the fore and aft nuts removed and the lower unit is at lease loosened (as evidenced by dropping 3/4 inch) then you are probably going to just need to work it free with your PB and gentle persuasion. Wooden wedges, like the shims you get for installing a door frame, are perfect for getting space between the lower and mid housings and minimizing the chances of damaging anything......

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

Thanks for the input Chinewalker. It seemed counter-intuitive to remove that bolt. Both of the attachment bolts are off. I haven't had time to really work at it but have hit it with PB a couple of times now.

As for the wedges, do door shims really work to push the two pieces apart? It seems like the wood would just crush. I'll give it a try though. Thanks!

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

So, I'm kind of at wit's end with this thing. It has been sprayed with PB, allowed to sit and then "gently persuaded" (followed by some not-so-gentle persuasion) several times and no progress. Still stuck with exactly the same amount of movement. I have even separated the mid-housing from the powerhead so that I could get better access to spray it with PB.

Unfortunately, I forgot to buy shims at the store today so that idea will have to wait another day or two but I can't imagine that they will provide me with more pressure than has already been applied.

Does anyone have any other ideas?

Also, if I disassemble the powerhead, will there be access to the driveshaft so that I could drive it out from the other end?

 

[Chinewalker]

Re: 1964 Mercury 39 lower unit stuck

You won't be able to disassemble the powerhead without removing it from the exhaust housing.

As for the wooden shims, if they're hardwood, they'll hold up. Stack them if you need to.

As a FINAL alternative, some folks have had to cut the driveshaft to drop the unit. This at least allows you to get the powerhead off...

Mercurys and their carbon-steel shafts. Gotta love them...

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

I still haven't gotten around to getting some wedges and trying that approach. I will do that first but, as another option, could I pull the propeller shaft, remove the pinion gear bolt and try getting the lower unit off of the driveshaft?

Then I could get the mid-housing off, get better access to the top of the driveshaft and get some heat on it...?

 

[Chinewalker]

Re: 1964 Mercury 39 lower unit stuck

Unfortunately, the waterpump housing would prevent you from pulling the unit off. The pump housing is bolted to the top of the gear housing and under that is a ball bearing, clipped to the shaft, so there's no easy way to pull the shaft out without dropping the unit...

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

So, just in case anyone reads this in the future, unscrewing the aforementioned screw that retains the shift shaft in the lower unit would have been a good idea.

After much effort with wooden wedges, I used a pickle fork intended for separating automotive ball joints and actually broke a chunk out of the inside of lower unit where that retaining screw used to go :facepalm:. It turns out that the shift shaft was stuck, not the drive shaft. I did get it apart finally, though! The shift shaft has about 3/4 inch of play for the O-ring to seat, so hopefully I can get it back together without any leaks. I just hope I can get the shift shaft back into the shift cam without disassembling the remainder of the lower unit...

 

[sutor623]

Re: 1964 Mercury 39 lower unit stuck

A lot of motors have a small screw that you can barely see, on the shift linkage rod. When you start to drop the motor it will get hung up. Just unscrew it enough to slip the linkage apart and VOILA, shell slide right out.

You mean this..... Hope you get er working well bud. They have some stuff called JBwaterweld made for underwater aluminum applications. If you sand the paint down and use it it should help keep that broken chunk together. If you have doubts, take it to the local welder. I have an aluminum welder around here that would charge around $40 for something like that to be welded. May save you a lot of time and $ in the long run. Good luck!

 

[Chinewalker]

Re: 1964 Mercury 39 lower unit stuck

Getting the shift shaft back in will require disassembling the whole lower unit as the plunger in the propshaft promptly pushed the cam out of the way when the shift shaft came out. No way to get it back in place without taking the unit apart....

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

Chinewalker- I thoroughly appreciate your expertise and input but I am no longer asking a question pertaining the ability to get the shift shaft back into the shift cam. It is possible without taking apart the lower unit - on my engine, anyway. I have done it 3 times now. I have not tried any other configurations for fear of your advice, but it appears that so long as both are in forward gear and you give both ends a jiggle as you put them together, you're good to go. Once again, on my engine...

sutor623- That's the one! Unfortunately, the piece that broke off, broke into several pieces. There won't be any welding going on... On the other hand, the shift shaft is so firmly stuck at the upper end, it seems to hold the seals in place and I don't seem to be having any water seepage issues (yet, anyway). I figure that I'm only into this engine for about $50, so if the lower unit oil has to be changed every couple outings, so be it. It's also just a kicker, so it's failing is only an issue if the Tower of Power fails too...

Now my issue is that I'm still not peeing. Everything has gone back together (and been taken apart and gone back together again), no water appears to be getting into the lower unit (two weeks in a bucket), the water pump pumps water (checked by turning by hand), the hole that appears to be the "tell-tale hole" is free from visible obstruction.

As far as actual operation, everything seems great: starts after only a couple pulls, idles nicely, shifts nicely. No high-revs yet (hasn't been in the water) but unless the hub slips, I think I'm set - other than cooling.

Is it possible that there is corrosion so bad in the water jacket that no water gets through, or is that unlikely? Any other thoughts?

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

Ok, so is it possible that this particular model does NOT have a tell-tale?! I had not heard of this before but I am something of a newbie to outboards... I did some more tinkering today as well as some youtube research and I think that this is a possibility. I'm wondering if anyone has a conclusive answer to this...?

I am definitely getting water to the powerhead. This is verified because - by something of an accident - I did not re-tighten the six bolts that hold the powerhead to the lower cowl and when I started the motor, water seeped out of the holes in the bottom cowl. My previous thinking was that a certain hole - which I have now verified is just an exhaust port - was the tell-tale hole.

I looked up several videos on youtube and some Merc 3.9's of similar vintage have the tell-tale coming out the starboard hole in the lower cowl, some the port hole, and some have none at all. I also found a video of a similar vintage Merc 6.0 with a comment from the owner that the model in his video lets the water out underwater. I also found Merc 3.9 video that did not make a claim about where the outlet was but that, although there was no tell-tale, the motor had a brand-new impeller and had no problems over about 15 hours of use.

I also looked at the parts fiche on SeaWay's site and there is a hose/nozzle combination - which seems that it could be nothing other than a tell-tale - listed for some models but the serial number range is subsequent to the serial on my engine.

So, the questions are:

Is it possible that my water outlet is under water? and, if so,

Where would I find it, to ensure that it is working correctly? ...or does it just sort of slop out the lower exhaust port?...

 

[sutor623]

Re: 1964 Mercury 39 lower unit stuck

Water exhaust is under water. Best way to see it is to run the motor on flush muffs if possible. In 1964 it was often that motors did not have a tell tale. Im not sure when they started putting those in....

 

[NWVintage]

Re: 1964 Mercury 39 lower unit stuck

Ok. I was thinking that I'd have to try to figure out something to actually hook water up to the intake hole. This motor has a water intake tube that sucks water in from under the cavitation plate (about where a trim tab would be on a larger motor), so I'll have to just hold a hose up to it or something.

Is there an actual hole that the water would be coming out of or would it just come out through the prop area?

From what I've seen, 1966 or so was the introduction of the tell-tale - at least on the Mercury 3.9's.