AllDodge

iTrader: (1)

Agree, this is my setup and may be the OP's
I had a MEFI-1 with VST and upon repower was changed to MEFI-3 ECM, cool fuel and harness. My injectors have 1 O-ring on top which fit into the rail, and a large single which fits into the intake. Just had the injectors cleaned and flow tested for this season.

BUP

iTrader: (9)

MEFI 1 was still used in 1998 with gen 2 cool fuel for big blocks Merc stock apps. Maybe I MISSED this no posting of the engine serial number from the OP.

The reason why. Posting engine serial numbers is the end all for what really one has for the engine and its complete set up and proper parts installed along with proper service procedures and specs. They are very important as all boat owners having an OEM installed marine engine - needs to know their engine serial number.

BUP

iTrader: (9)

1998 gen 2 cool fuel

MerCruiser 502 Mag MPI Bravo (Gen. VI) GM 502 V-8 1998 Fuel Pump & Fuel Cooler Parts

BUP

iTrader: (9)

same group of engine serial numbers and 1998

MEFI 1 used with gen 2 cool fuel

MerCruiser 502 Mag MPI Bravo (Gen. VI) GM 502 V-8 1998 Electrical Box & Components Parts

BUP

iTrader: (9)

same 1998

using gen 2 cool fuel using, mefi 1 and longer Japan made fuel Injectors

MerCruiser 502 Mag MPI Bravo (Gen. VI) GM 502 V-8 1998 Intake Manifold & Intake Plenum Parts

AllDodge

iTrader: (1)

Guess I'm messing something but
1993-1995 used intake 805233A2 then later changed to 805233A6 and MEFI-1
1996 was switch over year between old and new 8M0090767 0K147349 and below VST and 0K147350 above cool fuel
1998 Later used intake 861300A2 and start with 0L085433 thru 0M024999 with MEFI-3 and new injectors
Genuine Mercury & Mercruiser parts. Intake Manifold and Intake Plenum

BUP

iTrader: (9)

Bob - what I posted it ends at 0L085432 engine serial number and what you posted the engine serial number starts at 0L085433 ----- just one more number advanced in the engine serial run can mean a complete system change in the mix. Why I will say it again, Marine engine serial numbers are the bible when one works on OEM marine apps and how the parts and set up are installed. Even specs can change from group serial number runs to the next group of serial runs.

BUP

iTrader: (9)

did not read all posts but seen the OP used gasket sealer internal for the t stat 100 percent do not do that - all flanges and mounting flanges need to be clean and as much rust fee as possible. Its a thin cork style gasket that seals the t stat against the flange in the housing. That needs to be installed correctly and NO gasket sealant used period no where - a piece of gasket sealant could have broken off and stuck in between the T stat causing it not fully close ever.

No sealer on anything nor on the gaskets period. Merc apps come with what supplies for coolant temp sender and sensors - the boat builder installs the gauges. Are you sure your temp gauge is reading correctly ? I see this off sometimes 20 plus degrees either way. Scan the engine to see what temp the engine is running to compare against the temp gauge on the dash. Also what is MAP readings ? Idle thru WOT ? prob why your running rich unless you really have a cold running engine all the time.

715517

Temperature problem is now solved. Changed temp sender from my old engine and now it runs 175F before thermostat opens. But still having rich idle.

Next week the boat is going to Mercruiser workshop for diagnostic scanning. They also are doing all the adjustments to throttlebody and ignition timing. I tried to put engine in timing mode by putting wire in diagnostic plug, between pins A&B but the engine shut off and didn't start up for few minutes. But it fired up after a long start and now it indles fine.

MAP sensor is new, and wiring harness is measured OK.

AllDodge

iTrader: (1)

Connecting those two pins together should not have done that. You sure those were the two pins?