Question: Can the engine make 15 inches of vacuum running on 4 cylinders? My computer EITHER has lost a driver OR is running in limp mode yet the shop is telling me my vacuum is good...Is this possible? They are also stating they believe my ECU is bad and needs to be replaced (MEFI 1).
Something doesnt sound right here....

Yes you can make vacuum running on 4. All it is, is piston going down with the intake valve open. Now if the intake valve is opening late and the exhaust opens early you will have poor vacuum. Its hard to say without being there in person, but I would be pulling the timing cover off and checking the gears. It not that hard to do. Eliminate one thing at a time. Just my 2 cents

I think I would start looking for a new shop, this can not be this hard.

I wish going to a new shop was the fix but this is the 4th shop the boat has been to in the past 2 months!! The engine was just torn down and rebuilt for the second time last week because of this issue. The cam was replaced as well just to make sure that wasnt our problem.

Put a vacume guage on it and move the distributor arounf to see if you get a stronger reading..that should kinda tell you which direction to go...

4 shops and your paying them for making mistakes? Ship it to chicago and ill fixx it

Just thought I would post up the end result. The cam that was INITIALLY installed was the wrong one which is why my vacuum was so low and why my computer was flipping out. It also turned out that my computer was bad (one driver was down--not sure how that happened because it was fine before the rebuild).
Once they got the engine fixed I thought I was in good shape but then my outdrive blew up....why? Because they had reinstalled the engine without the springs and washers (and without 1 of the engine mounting bolts)...This caused alot of stress on the drive which gave up on my 3rd time out (after the engine repair).
I ended up doing a full dispute on my visa and had all of my money returned to me for the engine rebuild. It cost my my entire summer but in the end I have a new engine and outdrive.

I don,t know how you can get the engine alined with out the
springs and washer(fiber) to get the drive installed. I had one fall into the bilge once when I was installing an engine and fought it for hours. Then I noticed them both in the bilge and problem solved.

You have had some bad luck. You might buy a manual and start doing some of the work yourself. There is plenty of great knowledge on this site to help with ANYTHING.

Thats the problem--they never removed the drive and reinstalled the engine!! Without the springs and washers there was alot of pressure on the upper gears and it actually broke the housing off that the gears sit on.

If the motor won't align, i.e. the drive shaft won't fit into the coupler the sneaky mechanic can hold the engine on a hoist and get the drive shaft into the coupler and then bolt it down. Drive lasts about as long as Powerquests did.

Woa Nelly, Time for a different shop.

your mechanic is doing r&r on engine without removing the drive,dont walk,but run from him,if he is to lazy to pull the drive,what else is he to lazy to do.just my 2 cents .