Offshoreonly.com - Donzi 377 scorpion timing/idle issue

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Quote:

Originally Posted by SB (Post 4800579)

Okay, if this is your intake manifold, then you have a Ford type iac (#33 in pic) near the back.
https://cimg5.ibsrv.net/gimg/www.off...158292b75d.gif

My IAC is on the throttle body, not the intake manifold. the lower half of my intake looks like that

Quote:

Originally Posted by hypforlife32 (Post 4800580)

My IAC is on the throttle body, not the intake manifold. the lower half of my intake looks like that

Oops. Okay. Forget what I just said. Let me investigate. Do you have correct engine link for mercruiserparts.com you can put here to save me time ?

Quote:

Originally Posted by hypforlife32 (Post 4800580)

My IAC is on the throttle body, not the intake manifold. the lower half of my intake looks like that

Okay. I have the diagram /parts microfiche
https://www.mercruiserparts.com/bam/...31458/2725/120

You can see IAC (GM pintle type) from frt of tbody with Flame Arrestor off. You can plug with your finger or etc too.
Give me a ring when you have time

Quote:

Originally Posted by SB (Post 4800584)

i will give you a ring here shortly.

Missed it. Was running and gunning to do dinner on the boat.

See what I mean about iac opening on frt side ? Take off arrestor and you’ll see it.

Quote:

Originally Posted by hypforlife32 (Post 4800486)

What’s up guys. So this may be a long one, but anyhow. I bought a boat back in may that had a cracked block on the port side. The starboard side runs fantastic. Smooth responsive no codes, service mode with a paper clip method works well. Even with a scanner too. I verified in service mode I have 8 degrees BTDC. Engine runs like a champ. Looks original with boat saying 440 hours but ecu reads 280.

now, onto the port side. Removed the engine. Found out it is a 383 already with the WRONG compression. Was upwards of 10.3/4:1. Luckily I did some math to find that out before getting a new block, piston combo. Had the machine work done and they assembled the long block. I did lifters, intake manifold and dressed it. Compression is 9.1:1 now which factory is 9.0:1.

I am have a very hard time trying to set timing on the new engine.

key on. Insert clip. Start, try to get base time where it needs to be. Even 5-6 the more is very responsive BUT out of service mode the idle increases?? I can only get about 1 degree and idle stay at 750 fully warmed up out of service mode. Is there any reason why increasing timing would increase idle?? I’m thoroughly confused. I’ve tried swapping throttle bodies. Map sensor. All from the good engine that runs. Similar results.

I did forgot to mention that I had to have a cam custom made to the original specs which I found same lsa 114. Same lift etc.

vaccumm on good starboard engine is 16 at idle

new engine is 10-11 at 0-1 degree BTDC.

VOLTAGE is 13.x

the map sensors read at 5hg diff as well. Would this maybe be a vaccum leak im chasing? To cause this issue??

when I get timing to 7 degrees idle is now up to 1500ish.

maybe I am doing something wrong?

Any and all advice would be greatly appreciated.

I know you are dealing a lot with the IAC but I would suggest that is not the problem. Start the motor WITHOUT jumping into base timing. THEN jump A/B to get into base timing and THEN manually turn the distributor to get 8 deg BTDC. Remove jumper and see what happens. Idle will usually increase during base timing, that is normal. If it runs away after pulling the jumper you likely have a vacuum leak. Double triple dog dare check the TB blade is fully closed and throttle linkage allows it to close fully as well.

On the same page.
That’s what I am having him/trying to have him do. :thumbs. Close down or block iac air so can see if /and where there is a vacuum leak.

How did it work out ?

Quote:

Originally Posted by SB (Post 4800855)

How did it work out ?

before the other engine had a miss it was doing 52 at 3400 rpm on the gps

FIXED! : IAC was not moving. had a bad connection with one of the wire. went right into service mode now and timing set! Took it out on the water. now the other engine has a miss.i cant win. pretty heavy miss. used a tester and all wires are firing. injectors where just freshened up and had a great bill of health. wonder if rocker or spring broke. 450 hours on this engine. Was planning on doing top ends over the winter.