Engine Alignment Help Please

[robertsapp]

What am I doing wrong? I attempted to align my 3GM30F the other day. Loosened bolts on coupling, feeler gauge indicated excess clearance on port side of coupling. Rotated coupling, checked again, still excess clearance (over .010) on port side of coupling. OK, what I've read says the front of the engine needs to move to port. I loosed the mounting bolts on the foward two engine mounts, and tap them slightly to port. No change at coupling. Move mounts more to port. Still no change at coupling. Move mounts again - now they're a 1/4 to 3/8 inch to port, still no change at the coupling. Then I notice that while I'm moving the front mounts to port, the actual engine position doesn't seem to be changing, the rubber in the mounts is deflecting to absorb the movement as I move the mounts, but the engine is staying put. I did NOT loosen the aft mounts, because I was afraid of shifting the entire engine toward the port side. What am I doing wrong? I need to get rid of a pretty nasty vibration. Do I need to loosen the aft mounts as well? Are they holding the engine in place, not allowing the front to move? Also, I noticed several of the lag bolts that hold the various mounts down appear to have stripped out, and don't grip very well (just spin in place rather than tighten down). Can I use a larger lag bolt to try and get some purchase in the stringers, or do I have to remove them and do an epoxy fill of the existing holes and redrill?

 

[Ed A]

you will have to get it all right before you can really fix it.
1. if the lag bolt holes are loose the engine is loose. Yes you can fill them with epoxy then wax the bolt and put it in the wet epoxy. you will still be able to move it when you need to.

2. The cupling has to be prefectly straight to be really right.

3. If you loosen the front to move it and the back holds it straight the back mounts are preventing it from moving. they will have to be slacked to let it move.
Don't be overly concerned about the back moving just unbolt the mounts and let them go where they need to be then bolt them down. if your up and down adj, is ok that makes it easier. You need to have the same reading all the way arround the cupling before you put the bolts in. Then bolt down the engine, then check it again and bolt up the cupling. Make sure the shaft in close to center in the thru hull tube.

I sometimes center the shaft 1st and put a block or scrap under it to keep it in the center of the tube. otherwise the shaft will drag on the tube thru the hull and cause more problems.

I hope this helps.

 

[SamLust]

Don't forget that if you adjust up and down using the front mounts the rear mounts act as the pivot point so your result is opposite.

Advice: Do not lean on the engine as you measure with the feeler. The mounts move enough so you'll never get it right, but you will make yourself crazy.

 

[Rick]

Hey Robert!
That is kind of a tough one. I have to admit, when I got my rig tuned, I hired it (engine alignment) out so I could watch the expert do it and get an idea for myself. Suprised the engine isnt shifting upon adjustment.
Have you identified the source of the vibrations? I assume you have, just curious.

So how is Eagle?

Shoot an email when you get time. Would like to catch up some.

cheers

 

[robertsapp]

Rick,

I keep meaning to sit down and write you an email, but life keeps getting in the way. I'm sure the vibration I'm experiencing is due to engine misalignment, helped by a worn cutless bearing and a two bladed prop. I'm hoping next year to haul the boat, pull the shaft, replace the cutlass bearing, true the shaft, balance the prop, and install new engine mounts. Then I hope to finally dial everything in sufficiently to stop the magic fingers in the cockpit while motoring.

Nice tip on using waxed bolts in wet epoxy - I wouldn't have thought of that. I'm guessing I can just rub them on some parrafin? Also, I'm still curious if I can just go up a size on the lag bolts, provided they still fit through the holes in the mounts? That seems like the quickest possible solution to a stripped mount bolt.