Yachtwin 4HP Stuck Lower Unit

[KC49111]

I'm doing some long overdue maintenance on the old family 1970 Evinrude Yachtwin 4HP (4036 or Johnson 4R70). I've undone the 4 bolts on the gearcase in order to check the water pump. The foot drops about 1/8" before the drive shaft stops with a metallic clunk. There's no shifter on this motor and the manual is no help. I thought I could just pull the foot off. Is there something else at the powerhead or elsewhere?

 

[Chinewalker]

Re: Yachtwin 4HP Stuck Lower Unit

Hi KC,<br /> Your issue is likely that the driveshaft is stuck in the powerhead. The "long overdue" description only confirms this as your likely problem. Over time the grease that was originally used to prevent the stainless steel driveshaft from making itself one with the steel of the crankshaft can work its way out and lose its effectiveness. Also, it is possible that a previous servicing may have neglected to re-grease the splines, or possibly too check and replace the o-ring that aids in holding the grease in place.<br /> In any case, I would recommend the following - apply gently increasing pressure to pull the driveshaft out of the lower unit, forcing the impeller key past the pump housing. It may leave a small nick in the housing, but won't permanently hurt anything.<br /> Now, you've got a motor with a driveshaft stuck in the powerhead. Using ViceGrips, grab ahold of the driveshaft in a spot that shows no evidence of bearing or seal wear. Better yet, remove the powerhead from the exhaust housing (four bolts at base of lower cowling) and grab ahold of it up above. Leave enough room between the Vice Grips and the powerhead so that you can tap the Vice Grips with a hammer to drive the shaft out of the powerhead. If it doesn't pop out easily, then you may want to use some Kroil or PB Blaster in the stuck area to facilitate removal. <br /> Once you do get it out, clean up the splines - both male and female and inspect them. Often, the rust will degrade the splines to the point where there won't be enough meat to bite into. <br /> For installing the shaft back into the unit, position the unit so that the propshaft points straight down. Usually, this will help position the pinion gear back on center so that the driveshaft will slide in. If not, just pull the rear of the gearcase off and align the gear that way.<br /> For reassembly of the unit back to the motor, be sure to replace the o-ring at the splines, and use a good waterproof grease liberally thumbed into the splines of the driveshaft.<br /> Good luck!<br />- Scott

 

[KC49111]

Re: Yachtwin 4HP Stuck Lower Unit

Thanks, Scott, that was very helpful. It sounds like I may be dealing with replacing the water tube grommets, gearcase seals, pump housing, etc as well. I'd better allow for more time and parts.<br /><br />The Evinrude impeller clearly needs to be replaced, but does anyone know what the water output from the lower unit should normally be. Right now it "spits" out the weep holes, but not with a lot of force.

 

[Chinewalker]

Re: Yachtwin 4HP Stuck Lower Unit

Hi KC,<br /> Most of the water exits the exhaust below the waterline. The misting/spraying you see coming out the exhaust relief holes in the leg is normal. It should be warm but not blistering hot.<br /><br />- Scott

 

[joe_morgan]

Re: Yachtwin 4HP Stuck Lower Unit

I'm looking at one of these on ebay at the moment. What should I look out for?

 

[Paul Moir]

Re: Yachtwin 4HP Stuck Lower Unit

Normal stuff - compression, ignition, lower unit water free. Great little eggbeaters though - those are excellent running engines when tuned up right. They are not, however, powerhouses. You can expect the performance of a modern 3hp.

 

[joe_morgan]

Re: Yachtwin 4HP Stuck Lower Unit

I ended up getting it for 185 Aud. That prolly 145 US. I'm happy.

 

[KC49111]

Re: Yachtwin 4HP Stuck Lower Unit

I followed forum/manual advice for carb cleaning, coils, spark wires and the little twin is running quite well. I had water coming out of the relief holes, but the engine seemed hot, so I followed CW's advice and pried the lower unit off with flat bars. The impeller was fine but set, but I found the housing was broken at the water tube bushing. I think just looking at the relief holes may not be enough, as some water must have been pumping out of the housing into the exhaust tube.<br /><br />2 problems still to solve:<br /><br />1) The 2 pump housing screw heads had broken off (I was able to remove the housing by breaking it into pieces with a screwdriver and hammer). I'm assuming I'm going to have to drill and tap them. Does anyone know if the screws are stainless or aluminum and what the thread size is?<br /><br />2) Predictably, the driveshaft is stuck in the crankshaft. I have the powerhead off and will try Liquid Wrench then vicegrips/sledge. Should I try to remove the exhaust tube for better access (pretty stuck) or just dribble down the shaft? Is heat likely to damage any seals? Just to confirm, there's nothing to line up to drop the shaft that I'm missing?<br /><br />Thanks

 

[Paul Moir]

Re: Yachtwin 4HP Stuck Lower Unit

Sounds like you're running at par. <br /><br />1) If you've got anything sticking out to work with, try putting vice-grips on them, hosing them with penetrating oil, and heat the lower unit with a torch (Mapp is better than propane). If they are broken flush then you'll have to drill and tap them out. Do not attempt to use any form of ez-out. The screws are #10 - 24 threads-per-inch and it seems to me they're 1" long or so (I can't quite remember that dimention). They are stainless steel. When reinstalling various bolts and screws, coat them in a non-RTV sealer so they'll come out easier next time. <br /><br />2) I would remove it - it shouldn't be bad compared to the powerhead 'bolts'. I should have mentioned something about an 'Impact Screwdriver' which is the tool to use on those cursed things. There are no lower crank seals so don't worry about the heat. Rather it just has a plain bearing down there and relies on the oil to make a good seal. This is part of the reason I run my 4hp heavier than 50:1. The nearest rubber seal is the top crank seal.<br /><br />Good luck with it! Give the penetrating oil time to do it's thing.<br /><br />PS - while the powerhead is off, make sure the passage that leads up to the cylinder's water jacket is clear. There is one water inlet and two water outlets on the block, and the one that I'm concerned with is near the head just left and below the bottom cylinder. There's another place that blockage can occur where the water passage runs across the top of the block, but that is acessable by removing the exhaust cover plate which is possible with the powerhead installed.

 

[KC49111]

Re: Yachtwin 4HP Stuck Lower Unit

Thanks Paul,<br /><br />I removed and cleaned the water tube, and blew compressed air through the water tube fitting with what seems like a clear return out the exhaust tube. Am I interpreting your PS correctly re the passage leading to the water jacket?

 

[Paul Moir]

Re: Yachtwin 4HP Stuck Lower Unit

No trouble at all. <br />Yes that's pretty well it. I forgot that the exhaust tube has to also be off before you can see the other passage. Last time I was looking at one was a year ago.<br />The idea is that there are two parallel cooling circuits on the 4hp block, and it's entirely possible for one to be blocked and still be able to blow through. The vast majority of the water travels up under the exhaust cover, goes across the top of the block, down the intake side and out with the exhaust. My guess is this mostly cools the exhaust in the leg. The other smaller part of the water gets into the cylinder's water jackets through a hole between the passage on the top of the block and the water jacket below. It circulates around the cylinders and head before coming out the small hole at the bottom (the one I suggested you make sure is clear). <br />I've seen a few 3 and 4hp engines where this hole has been blocked, and so water would seem to be circulating normally (all through the first circuit) but is not actually cooling where it's needed. These engines all overheated only after running WOT for a few minutes.

 

[BF]

Re: Yachtwin 4HP Stuck Lower Unit

Hi KC... (& welcome)<br /><br />I don't know that particular model, maybe I'm wrong, but could it be that it is a model that has a spring pin running perpindicular through the driveshaft up near the top?? My '75 6hp has that, the lower unit drops about 1/4 of an inch, then you need to turn the flywheel slowly (helps if plugs are out) until the perpendicular pin lines up with the appropriate slot up under the power head. The shaft will only drop (or go in) when the cross pin is perpendicular to the prop shaft. That cross pin suppossedly holds some cup/spring assembly up that is part of the lower crank seal.<br /><br />Of course if there's no give at all up and down in the driveshaft it probably siezed, but if it clunks up and down a bit, I'd bet a loonie that it has a cross pin up there. <br /><br />good luck.<br /><br />Brent<br /><br />---just re-read your post, a "metallic clunk" is exactly what mine sounded like when the cross pin was not aligned... (I just did my 6hp last night)--

 

[Chinewalker]

Re: Yachtwin 4HP Stuck Lower Unit

BF - No cross-pin on the 4hp...<br />- Scott

 

[BF]

Re: Yachtwin 4HP Stuck Lower Unit

dang... guess I owe a loonie (which is $1 for you non-canucks)

 

[Chinewalker]

Re: Yachtwin 4HP Stuck Lower Unit

Hi BF,<br /> Note the source of my tag-line... from a few boys in Kingston, Ontario.... I spend a fair amount of time (and Loonies!) in Canada, although the furthest west I've been is Windsor... I hope to visit the Praries someday....<br />- Scott

 

[KC49111]

Re: Yachtwin 4HP Stuck Lower Unit

After 3 days of soaking in LW then banging on the shaft far harder than I would have thought, I finally got slight motion on the driveshaft. A few more hits in and out and it came free as if it was never stuck. Fortunately there seems to be enough spline material left. An impact driver helped remove the exhaust tube, but I can only see one of the outlet holes Paul mentions so far.<br /><br />I'll let the shop drill out the broken water pump screws. Thanks all for the advice. There is a fair amount of carbon in the exhaust outlet so I'll have to research whether to try to decarbon with Engine Tuner or manually with the head off.

 

[Paul Moir]

Re: Yachtwin 4HP Stuck Lower Unit

IMO, Use the engine tuner stuff. The real trouble with carbon (other than plugged exhausts) is that the piston rings themselves get coked up and stick in their lands. Decarbing with solution will clean up this area too.<br /><br />I'll see what I can do about a pic of that location.

 

[joe_morgan]

Re: Yachtwin 4HP Stuck Lower Unit

This has been an excellent thread. Followed it for a couple of weeks now. I've printed out a copy so I can read it while I do my water pump.<br /><br />joe

 

[Chinewalker]

Re: Yachtwin 4HP Stuck Lower Unit

Just noticed one of KC's queries that I overlooked - the screws that hold the pump housing in place are stainless steel....<br /><br />- Scott

 

[KC49111]

Re: Yachtwin 4HP Stuck Lower Unit

The engine is back together and runs well in the tank. I'll put some more time on it later this summer to make sure my work holds up and fine tune the mixture (WOT in a tank with only forward gear is a bit exciting). In the end, the overdue updates this little engine needed were:<br /><br />-Remove stuck lower unit due to driveshaft rusted into crankshaft by pulling it through the water pump, then knocking the cast water pump apart. I was lucky enough that the pinion gear in the L/U stayed in place even though I had the shaft in and out 2-3 times and knocked it about a bit. I didn't want to risk the lower unit by trying to drill out the stainless screw stubs in the soft aluminum, so I took it to my pet machine shop. It cost $$ (an hour of shop time), but a milling machine with a carbide bit allowed for a perfect cleanout and re-tap. The replacement pump is still cast aluminum,surprisingly.<br /><br />-Head Gasket - This was more preventative maintenance in case the head had warped. It came off in one piece. There was surprisingly little carbon, and that came off when sprayed with Engine Tuner. The pistons and rings seemed fine, but there was enough salt blockage to clean that it was worthwhile. I surfaced the head on a cutting board with 240 wet or dry sandpaper and reinstalled it. I ran some more Engine Tuner through the carb to hit any carbon left in the rings.<br /><br />-Plugs<br /><br />-Spark wires and boots - had been frayed for as long as I can remember. WD-40 (or hairspray) is a good lube to work the wire through the boots.<br /><br />-Coils - didn't seem to arc to ground, but were cracked.<br /><br />-Fuel Pump clean - this may be the next preventative replacement. Far too many small parts to play with again.<br /><br />-Carb rebuild - all the seats were still OK after 35 years, but it was time to update the float/washers, etc. Even though it looked clean, some varnish still came off with carb cleaner. A low idle problem was fixed by knocking out the welsh plug/cap and cleaning there. My first cleaning wasn't enough, the improvements came the second time.<br /><br />-Mid Housing - steering had always been very stiff. Taking out the 4 bolts to split the housing and applying grease to the bearing surfaces has made an unbelievable improvement.<br /><br />If the crankshaft/pistons don't blow, there isn't too much left to replace. After 35 years of off/on service anything else is a bonus. Although the parts weren't cheap locally, the savings on shop labour were huge even before considering the education benefit. Plus this was the first motor I was allowed to run on my own long ago, so I probably owed it something.