Merc 4.3 can't align engine

Discussion in 'Gas Engines' started by wood45s, Jul 16, 2017.

  1. wood45s
    Joined: May 2017
    Posts: 10
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    Location: ga

    wood45s Junior Member

    Merc 4.3 can't align engine

    1995 Starcraft Islander 221 recently purchased. The engine was rebuilt summer of 2016 with Chev s10 block and rebuilt heads by previous owner. It has not been on water since rebuild; only run with water hose on it some when engine was installed. They didn’t remove stern drive to install engine or check alignment. I immediately removed stern drive, fixed starter, etc. and test ran engine with water hose connected to thermostat housing. Seems to run ok.

    I can’t get engine aligned yet. I am using alignment tool inserted thru gimbal bearing. Bottom line is can’t insert the tool into coupler with rear engine mounts torqued to specs 40 ft-lb. If I loosen the rear engine mount bolts I can insert the alignment tool fully. Then I tighten rear engine mounts again and alignment tool will not go into coupler, not even a little. I raised and lowered the adjustable front engine mounts a half turn at a time and never could get the tool inserted when the rear mounts are torqued down.

    Maybe a washer or something was left out when the engine was installed. The only wood is a couple of ¾ plywood spacers for the engine mounts (front and rear) which are attached to the aluminum stringers/framing of the boat. The plywood spacers look original and appear to be in good shape best I can tell.

    Maybe I should lift the rear of engine and put in a washer for spacer and try that?
    Any ideas?
    I will replace the gimbal bearing, but was trying to get initial alignment done with the old bearing.

    Thx,
    wood
     
  2. wood45s
    Joined: May 2017
    Posts: 10
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    Location: ga

    wood45s Junior Member

    I forgot to mentionabove that I am using a 1 inch pipe thru the gimbal bearing to indicate which way adjustment should go until i can get the alignment tool to insert. The 1 inch pipe appears to be very close to centering the gimbal bearing now. It was off a bunch at first
     
  3. PAR
    Joined: Nov 2003
    Posts: 18,602
    Likes: 377, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've just aligned this engine/drive combo (4.3 and 2nd gen Alpha) last week and it can be a challenge for the novice. It sounds like your transom is soft, because you're getting movement when you tighten the transom plate bolts.

    First off, you need to start on a level playing field. The transom plate and the gimbal/bell housing assembly need to be married and torqued to spec, before the engine goes in. Once this is set, you drop the engine on, so the rear mounts are on and the bolts torqued down. With the engine dangling from the center lift ring, the front of the engine (the only place you should make adjustments) can be lowered or lifted to make alignment.

    Most can just eyeball the coupler through the gimbal bearing to get it close enough to insert the tool, though a 1" pipe will do in a pinch. Start by trying to identify which way you need to go (up or down) then just start moving the mounts (both at the same time) 1/2 turn, until you can nail it. Once it goes in, you can fine tune the alignment. My last adjustments were made in "one nut flat" increments. Once you get a "good read" on the tool, bump the engine over 90 degrees and check again. It's aligned if you can bump the engine around a full revolution and the tool still gives you a good read. Lastly, it's not aligned unless it's tight and gets the full revolution and tool read. Doing adjustments with loose mounts is not going to help.

    A cute trick I've used in the field previously, is a bigass (technical term) turnbuckle. I dangle the turnbuckle from the hoist and "D" shackle it to the center lift ring. This lets you very precisely raise or lower the front of the engine.
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Check the rear mounts to make sure they are not collapsed. That is a usual problem that won't let you align the engine.
     
  5. PAR
    Joined: Nov 2003
    Posts: 18,602
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've found it's not the rear mounts so much as the parts in them. There's some cork or felt washers, a double wrapped lock washer, etc.
    [​IMG]
    These parts are easy to mis-align or get crushed. Many I see are over torqued and the aluminum spacer can crush, causing the rear mount to be too low. In fact, any time I pull an engine that has some age, these parts just get replaced as a matter of course.
     
  6. wood45s
    Joined: May 2017
    Posts: 10
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    Location: ga

    wood45s Junior Member

    PAR, The transom to gimble housing seems to be tight. I tightened the bolts another half turn. I’ll put a torque wrench on and check tightness.
    I can still insert alignment bar only with rear engine mount bolts loose, no matter how I adjust up/down the front mounts.
    I’ve never seen the rear mount parts other than pictures. I can see the fiber washer, which I guess is glued in like the Merc manual says should be. I don’t know if the double wound washers are there or not. The spacer and large washer are in place.

    H. in the pic above is a locknut. How is the locknut held in place? I’m just concerned that if mount bolts are removed that the locknut may be lost.

    I’m rigging up a lift but will have to attach to a tree (already have limb chained to tree trunk for strength reinforcement), then lifting maybe an inch and see what’s the rear mount parts look like and maybe replacing them.

    Also, with the 1” pipe in the gimbal it looks like the pipe is slightly to the left maybe 1/16-3/32 inch as if engine is rotated slightly clockwise looking down at engine – meaning the 1inch bar is 1/16-3/32 inch closer to left than to right side of gimbal bearing.

    Gonzo, thx. There are no rear mounts other than the engine to inner transom plate as shown in the pic above. So I will assume by collapsed mounts you mean the parts in them as PAR is suggesting.

    Thx,
    wood
     
  7. PAR
    Joined: Nov 2003
    Posts: 18,602
    Likes: 377, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The lock nuts (H) are "captured" with a set of fingers on the lower portion of the transom plate, where the bolt goes through. If the engine is stripped and you can get around the steering gear, lift the engine, so the rear of the engine is clear of the mount and check to see the nuts are there. The bolts will not tighten down if they're not in place properly. The bolts are "self centering", so you can't screw up unless using an impact wrench for initial threading.

    If the engine is off side to side, you'll have to move the forward mounts, side to side too. There is some play with the front mounts, but not much, though often you don't need much. The front mounts have a fixed hole in the back and an elongated hole in the front. Loosen all bolts or lags and use a pry bar on the stringer, pushing against the engine or mount to shove the beast over just a touch, then dog it down and check again.

    If it looks low when the rear mounts are tightened and better when they're loosened, then the front of the motor need to go down. Drop the front mounts 1/2 turn each until you get it to look like it does when the rear is loose. From that point, go 1 1/2 or two flats at a time until you're able to get a good read on the tool. You might need to sneak up on it during the last adjustments, one nut flat at a time, but it sounds like the fronts need to go down a fair bit.

    In all honesty, you should pull the engine (I know this sucks, but just hoist it clear enough) and check the rear mount part condisions and their assembly sequence. I'll bet you're missing something or there's a crushed washer.

    Hell, you're in Georgia, spend a day, bring a six pack and we'll get that sucker done. I still have the portable (who am I kidding it's 12' tall and 10' wide) hoist in the driveway ('cause it's heavy and I've been too lazy to put it away yet). Sometimes it goes easy, a few adjustments it she slides in like your favorite ex-girlfriend. More often than not, we'll kill the six pack in the process of cursing and beating on it, until it lines up. I'm about an hour above Orlando. Then again, most shops only charge $50 - $100 for a simple alignment (not drive mounting, gaskets, etc., just the alignment).
     

  8. wood45s
    Joined: May 2017
    Posts: 10
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    Location: ga

    wood45s Junior Member

    OK, thx for the suggestions on this.
    I finally hooked hoist and lifted the entire engine about ½ inch then set it down again. Must have seated in a different position from before because it’s not left but in center. Some adjustment of the front down is all that was needed after bolting the rear mounts tight. It appears that a range of about 3 to 4 turns of front adjusters gives good insertion and easy rotation of the alignment tool, so I just centered it in that range.

    New problem when cranking after alignment with still no stern drive installed – I think the timing may have been advanced too much. It appeared to kick back and stripped the starter bolts out. I’m starting a new post on that problem.

    thx,
    wood
     
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