I'm about to yank the motor out for a change over from the flexplate that I have on the 383 now to a new light-weight manual trans flywheel. I'm removing the flexplate because the idle needs to be too high in order to keep it going at low speeds when shifting. The heavier flywheel should help me out there I believe.

Here's my plan...

Remove front accessory drive and the manifolds.

Remove power steering and alternator assmebly and set it out of the way.

Remove drive cables assemblies (wiring) and throttle cable.

Unbolt engine from the transom assembly and stringers.

Lift up engine slightly and slide forward enough to get the cover plate off and r&r the flywheel.

Reassemble.

Notice that I said nothing about removing the drive. I "think" I 'll be able to slide it back on there. Alighnment has never been an issue with this boat and in the three years that I've had it the alignment has never changed. Is this do-able without removing the drive?

Comments? Suggestions?

Thanks!

it is do-able!! We used to do couplers with the boat in the water.

My pop had a 26 Sea Ray that had a rotted stringer....we found this out after blowing 4 couplers. Anyway, we ended up being able to change the coupler with the boat in the water. We put a 6x6 across the boat, and hung a come-along off of the 6x6. Unhooked some accessories, and slid the motor forward.
It was kind of a pain reaching back there for the bolts..you had to kind of go by feel. But i think it would be the same process to swap the flywheel.
And the alignment shouldn't change at all.

sounds like your on the right track. I would pull the drive for reassembly but have seen it done both ways. I have also heard of people changing flywheels and the motors shake real bad . They have told me that it makes a difference if the motor is balanced internal or external. might be some thing to look in to.

Thanks for the comments...

The first 383 that I had was internally balanced. This one is is externally balanced. Anyway, I have the correct 400 flexplate now and I also have the correct 400 flywheel (quite the expensive sucker). I'm really dreading taking it apart since I'm trying to be out on the water. It's about to rain here so it looks like I'll be thrashing on it sometime tomorrow afternoon. I hope it won't take too long and that I'll be able to get it done during the afternoon and evening. We'll see what happens.

Ya know, it would be nice if the weather forecasters could tell you that it's definitely going to rain or not. Last report I saw was, "A chance of a sprinkle otherwise fair..." What I got was a freakinng down-pour and lightning and thunder and wind (that blew my flag over on the house). Can they ever get it right?!?

Also, can anyone make a hoist that's wide enough to clear about three feet in the middle?? The hoist that I borrowed from a friend has one leg hanging in the bilge (braced by a 3x3 at the edge of the bilge) and is no where near sturdy.

I'm half done with getting the flywheel off... I have four nuts left and she'll be ready for reassembly. I think I'm going to yank the drive off (since it's so easy to put back on) for reassembly. With the hoist barely making it I don't think I'll be able to slide the coupler back on there without a lot of trouble.

I'll report again later.

OK, just in case anyone is interested...

Well, after going in for a couple of hours for dinner I went back out and changed out the flywheel and then started buttoning it all up. I started to set the engine back, the hoist slipped and the engien bumped the drive shaft. No way of getting it back together with the drive off. Also saw that the drive shaft was cocked downward. So off the boat I go to remove the drive. Well after a good half-hour fight I got the drive off and found... an out of whack gimbal bearing! Luckily, I was able to reseat it and all is well. I went and got the engine back in with little trouble. All that's left to do is to bolt everything back up and then reinstall my seats and lower ice chest... and then of course the drive.

Time invested so far for changing the flywheel... seven hours. I will never do it this way again!

so now that the flywheel is changed is there any changes?

cmon Tom we need updates!!

I have not run it yet. Tomorrow is my b-day and as such my wife had planned on taking us out to a very nice restaurant for dinner this evening. I go it all buttoned back up and got the call to come in and get ready to go.

We're going out in the morning to try it out. I'll let you guys know then. I figure I went up about ten pounds in rotating mass... should be able to tone the idle down some as well as keep the engine running when I shift.

Total time to do the whole job (including reassembling all of the cockpit seating)... about ten hours.

Later!

Changed it, ran it, liked it.

Idle is better and the engine stays running. It doesn't rev as quickly as it did, but it's better than it was when it had the monster Merc flywheel. I still have speed, prop, and (mostly) tuning issues to deal with.

I switched back to my 17P Mirage prop (which is HUGE diameter-wise) and was able to crest 5k RPM. That small block is screaming at that point! However, I ran into some ignition breakdown at anything past that. I don't know for sure whether it's a matter of low voltage at the ignition, a crappy Thunderbolt IV system, or what. I haven't tried messing with it yet to figure it out. I may have been leaning out on the top as well (though my ever-so-slightly black transom would mean otherwise). Still I managed about 50 MPH (again) with the 17P and got the engine closer to its peak power. The mid-range though is, for lack of a better expression, explosive. The boat (keep in mind that this is not a go-fast hull at all) rockets out of the water and gains speed so quickly... there were a few times when it was just too much to handle.

Anyway, I'll probably mess with it some more during the week and report back over the weekend with how iit does.

Any suggestions on the ignition failures? Does the TB IV have a rev limiter or fall short of being able to supply strong voltage at high RPM?

Later,