Lower Unit Stuck - 2005 MFS15B2

[THudson]

Bought boat with 2005 15hp Tohatsu tiller/pull start. No history on prior owner's service. Want to change impeller but cannot get lower unit off. 4 nuts and spring pin holding shift rod have been removed. It does not budge and cannot even see any separation at seam. I've had it hanging upside down for about a week, sprayed PB blaster into water intake hoping some would work down thru pump housing onto drive shaft and into splines at crankshaft.....no luck. I would really appreciate any thoughts on next steps to consider??? Thanks!:facepalm:

 

[Sea Rider]

Re: Lower Unit Stuck - 2005 MFS15B2

Welcome to Iboats,

That's very bad news, ideal would be to have a small opening between lower and middle leg to place thin wedges to start with and open middle leg throughout, then work with thicker wedges untill drive shaft and LU pops out. What about bolting LU back on and removing complete power head, once all 4 bolts are free try to grab and pull head upwards to see if it pops out.

Or place engine upright, see if you can bang AV plate hard with rubber mallet so to have a small middle opening and work your way thoughout middle leg. Will need tons of patience, patience and more patience to work it right. Grease well shaft splines when assembling LU back. Good Luck.

Hasppy Boating

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

Odds are the drive shaft splines are stuck in the crank shaft. That can also happen if the drive shaft has been twisted from striking an underwater obstruction. Don't bang on the antiventilation plate -- that will just crack the casting. Either get wedges in to pull the LU down, or try to pop the power head off. You can also hang weight to persuade the LU to separate. Much patience (days) may be needed.

 

[Sea Rider]

Re: Lower Unit Stuck - 2005 MFS15B2

Definitely drive shaft is completely stuck on crank shaft, that's why is mandatory to remove lower unit and prop shaft to lube them well to avoid unwanted free trouble when sitting or using engines for long time periods without periodic lubbing these 2 critical poits that contacts metal to metal.-

Remove lower 6 bolts, turn crankcase in small right/left circles while pulling carb and cylinder head up and down while holding both extremes, must be performed with decission, repeat several times, let's hope all for a probable Bingo!!

Happy Boating

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

Odds are the drive shaft splines are stuck in the crank shaft. That can also happen if the drive shaft has been twisted from striking an underwater obstruction. Don't bang on the antiventilation plate -- that will just crack the casting. Either get wedges in to pull the LU down, or try to pop the power head off. You can also hang weight to persuade the LU to separate. Much patience (days) may be needed.

Patience is absolutely the right word. I started with an thick bladed butcher knife at seam at front of motor and now up to plastic toilet wedges wrapped in thin copper to keep them from snapping or shaving themselves down as they go in.

Here's pics on current. From what you can see, how much further will that opening need to get before the shaft is separated...just trying to get an idea on where I am on this journey (Day 3)? Keeping the 4 nuts loose but on to keep it from falling while I'm not there. Thanks!

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

Congrats. You are on the right track. Expect to need about an inch or so, maybe 1-1/2" for the driveshaft splines to clear the crankshaft. It may go easier as the engagement becomes less and less.

Once apart, inspect carefully to confirm that the driveshaft is not twisted. That's typically seen at the base of the splines, which would look "barber-poled" if twisted. When reassembling, grease the splines of the driveshaft to facilitate future removal. Don't get grease on the end face of the driveshaft, as it could get liquid-locked inside the crank shaft cavity, making it impossible to get full engagement when reassembling.

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

Congrats. You are on the right track. Expect to need about an inch or so, maybe 1-1/2" for the driveshaft splines to clear the crankshaft. It may go easier as the engagement becomes less and less.

Once apart, inspect carefully to confirm that the driveshaft is not twisted. That's typically seen at the base of the splines, which would look "barber-poled" if twisted. When reassembling, grease the splines of the driveshaft to facilitate future removal. Don't get grease on the end face of the driveshaft, as it could get liquid-locked inside the crank shaft cavity, making it impossible to get full engagement when reassembling.

Thank you! She finally gave in last night. This whole thing began with a broken upper shift rod (curved tip broke inside cowling where it fits into linkage). Was hoping removal of LU would accommodate replacement but now understand I need to pull power head to remove...thankfully I was able to loosen the the 6 bolts but haven't done anymore yet. If you have any tips or things to watch for on this next move it would be appreciated!!! Definitely a learning experience for this first timer.

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

You may be able to swap out the shift rod without power head removal. It's cramped in there, but with dexterity, you may get it. Might need to unbolt the shift lever shaft. Bigger question would be why/how it broke. You cannot shift (especially into R) if the drive system isn't turning. Typically, on tiller models of the 15, that results in a bent shift lever rod between the shift lever and the shift arm, but I suppose the shift rod could go.

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

You may be able to swap out the shift rod without power head removal. It's cramped in there, but with dexterity, you may get it. Might need to unbolt the shift lever shaft. Bigger question would be why/how it broke. You cannot shift (especially into R) if the drive system isn't turning. Typically, on tiller models of the 15, that results in a bent shift lever rod between the shift lever and the shift arm, but I suppose the shift rod could go.

You may be right on not removing powerhead but too late now, dealer and Alan from Tohatsu both advised necessary. I'll know more once I get the powerhead back on now that I see how it all fits together. Shift lever rod (from shifter to linkage under cowling) looks good, picture attached. I believe this may have been my own fault. With thieves seemingly everywhere, I used a 3/8" chain and ran it between upper shift rod to lock motor to trailer. It's only when I leave it out overnight somewhere and thought I was gentle but undue pressure may have weakened the rod at bend point going in to linkage. That's what I hope anyway.

Do you have any advice on remounting the powerhead by myself? I'm waiting on the 2 outer gaskets (#29) from dealer and just cleaning everything until they arrive. By the way, of all the advice I've been provided, you are tops! Thank you!

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

I would definitely defer to Alan's recommendations.

The base gasket doesn't require any special sealer or anything. Just be 100% sure that all sealing surfaces are perfectly clean and smooth. Also clean the bolts, and apply blue lock-tite when reassembling. I recommend using a torque wrench when remounting, to get even gasket compression. The aluminum block requires a surprisingly low amount of bolt torque. Confirm the adjustment of the neutral safety (recoil lock) cable, as accessing the adjusting nut can be a bit cramped after the power head is in place.

The 15A2 should have transom bolt lugs on the transom clamp. If so, installing those bolts will be a pretty good theft deterrent, especially if you use either anti-theft nuts, or ding the threads so that removal takes too long for the average thief to waste time on your motor.

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

I would definitely defer to Alan's recommendations.

The base gasket doesn't require any special sealer or anything. Just be 100% sure that all sealing surfaces are perfectly clean and smooth. Also clean the bolts, and apply blue lock-tite when reassembling. I recommend using a torque wrench when remounting, to get even gasket compression. The aluminum block requires a surprisingly low amount of bolt torque. Confirm the adjustment of the neutral safety (recoil lock) cable, as accessing the adjusting nut can be a bit cramped after the power head is in place.

The 15A2 should have transom bolt lugs on the transom clamp. If so, installing those bolts will be a pretty good theft deterrent, especially if you use either anti-theft nuts, or ding the threads so that removal takes too long for the average thief to waste time on your motor.

May I ask your preferred method to remove old gasket material? I see things on internet, whiz wheel (yellow wheel with plastic tips), sanding block, etc. Don't want to mess up soft aluminum so currently only trying gasket remover foam and a plastic putty knife....not working real well.

 

[dkonrai]

Re: Lower Unit Stuck - 2005 MFS15B2

i use a razor blade to get as much off as possible. you need, sharp good quality blades and go easy. then i do the stainless brush and carb cleaner route. your lucky you dont live in california. i cant get any chemicals that work as we have this whole green thing going on.
dino

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

You are on the right track. A blunted screwdriver can be "pushed" through the old stuff, and there are actual "gasket scrapers" available from pro tool folks. Big thing is to "push" the debris off, rather than trying to "Pry" against the aluminum. Sometimes, carb cleaner will help soften the old gasket.

 

[Sea Rider]

Re: Lower Unit Stuck - 2005 MFS15B2

Before bolting cranck case back to pan, could take advantage and torque with torque wrench all cylinder head back to factory specs, after old gasket left over is complete removed, polish both upper and lower metal surfaces that contacs gasket with thin metal particles sanding paper for a smooth finish. Don't know about 4 strokes OB's, but in 2 same model you need to apply a thin coat of gasket former, mega gray type on new gasket's both sides for a perfect seal to prevent water from leaking on pan through gasket.-

Happy Boating

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

Thanks, good thought on torquing bolts. I've got the old gasket off but the staining is a problem. Primarily around what I believe is the exhaust and water ports. I was thinking non metallic scotch brite pad and carb/brake cleaner but haven't tried yet. Sand paper with thin metal particles (where would you get this?) sounds tricky as it may remove aluminum as well. The gaskets removed didn't appear to have any sealant involved and the 2 outer gaskets were fairly thick. Obviously I'll double check with dealer when I pick up new ones. Getting those stains off is task at hand.

 

[Sea Rider]

Re: Lower Unit Stuck - 2005 MFS15B2

It's the opposite sanding paper used for wood, the one with microscopic metal filling. Get a very thin grade and with patience polish whatever part is non flat, still pourous, whatever. Alum is rock hard, no need to scrape it off, just smooth polish to seat well engine lower gasket. Check about if in need to apply a slight coat of high temperature gasket dressing. Poke with a wire, long tie wrap all holes seen on posted picgture, specially the in-out peeing hole.

Happy Boating

 

[pvanv]

Re: Lower Unit Stuck - 2005 MFS15B2

The staining is no big deal, and will not affect sealing.

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

The staining is no big deal, and will not affect sealing.

Thank you!!!

 

[THudson]

Re: Lower Unit Stuck - 2005 MFS15B2

I would definitely defer to Alan's recommendations.

The base gasket doesn't require any special sealer or anything. Just be 100% sure that all sealing surfaces are perfectly clean and smooth. Also clean the bolts, and apply blue lock-tite when reassembling. I recommend using a torque wrench when remounting, to get even gasket compression. The aluminum block requires a surprisingly low amount of bolt torque. Confirm the adjustment of the neutral safety (recoil lock) cable, as accessing the adjusting nut can be a bit cramped after the power head is in place.

The 15A2 should have transom bolt lugs on the transom clamp. If so, installing those bolts will be a pretty good theft deterrent, especially if you use either anti-theft nuts, or ding the threads so that removal takes too long for the average thief to waste time on your motor.

Gaskets finally came in and getting it put back together. I bought service manual but darned if I can find torque specs for 6 bolts to remount power head. I have them at 17lbs now and would appreciate your thoughts on correct torque per your comment above?

 

[TOHATSU GURU]

Re: Lower Unit Stuck - 2005 MFS15B2

If you got the factory manual the torque specs are in the front section by bolt size...Probably on page 15 or 16.