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Somone throw some ideas at me 4.3l merc hard start

3K views 20 replies 7 participants last post by  2000_WJ 
#1 ·
I know this is not a boat forum but I know there are a lot of guys here that know their sh*t! Not to mention I hate boat forums those pompous aholes do more picking, b*tching than answering your questions.

I have a 91 4.3L merc in a open bow that I just did a vortec head, aftermarket cam and 4 barrel conversion on. It was having an awful time starting so I double checked timing, spark, fuel etc. I even disconnected the exhaust elbows to see if the flapper valves had come off and were sitting at the base of my outdrive. With the exhaust disconnected before the Y the engines fires right up. I put the exhaust on it and it wont start WTF?
 
#4 ·
Well 2000wj
I am going to guess that you are 180 off on your timing,either at the timing chain or the distributor.
Pull number one (firing) spark plug, put timing marker on top dead center, remove distributor cap, check to make sure all are correct, number one (firing)cylinder is at top dead center,rotor is in line with number one firing cylinder (check firing order)
Valves to tight or to loose maybe?
Did the engine run before you tore it down?
JR
 
#8 ·
Did the TDC check, went over firing order, there is no lash adjustment on a screw in stud vortec head. I have never had this engine running, bought the boat 2 years ago and replaced floors, electrical top half of the engine interior. Basically everything in the boat except the short block. I did a compression check and have 120lbs on 4 cylinders, 80-90lbs on the other 2.

At one point the distributor was 180 off so I set the engine at TDC installed the distributor so the rotor pointed at number 1 double check firing order for the plugs and made sure the wires went to the right cylinders.

Why would the engine start with the exhaust from the flapper valves back start but not start with the exhaust fully bolted on? Would the engine fire with the distributor 180 off? I thought it would just back fire thorugh the carb.
 
#10 ·
Well I am with kj kyle
I am guessing now that theres a real big nest built in your exhaust system!!!!
Or the flappers are stuck shut!
Did the boat set with the exhaust system left open for a critter to get in!?
the exhaust boot down by the out drive also could be missing or torn enough so a critter could get in!?
Fun stuff!!!
 
#11 ·
Cooling system sounds good!
Check at the drive, drive tilted all the way up, torn boot or opening to the exhaust area, take a shop vac and hook it to the exhaust boot or opening, remove the exhaust elbow at the engine take a coat hanger (if you can find a metal coat hanger and try to remove the nest, being careful not to damage the flappers.
flappers could be in backwards? not likely, but could be, if you never ran the boat
JR
 
#17 ·
Tilt the drive up, and make sure the exhaust bellows attached to the outdrive from the gimbal isn't chewed away. That may be the entry point for nests....Setting that long it could be plugged with anything.

Pull the engine entirely and then the Y-pipe and see where you are at.

If you've got an overhead hoist it's an easy job I've done a few myself.
 
#19 · (Edited)
I wouldn't the douche bag will never give you an answer because he has no clue himself other than what his lazy as$ googled because more than likely the loud mouth prick never turned a wrench more than ten times in his life and takes his sh*t to the Marina where he gets as* raped by the "marine technicians" and probably his wife which is why he's a flaming dick job any way...

UPDATE The boat runs great, removed the flapper valves (very rough looking. Ruber gasks were iin pretty awful shape), power washed hundreds of zebra muscle shells out of the out drive exhaust and y pipe base, installed a new outdrive water pump impellar, changed the outdrive gear lube, installed Edelbrock 1409 carb with 1485 re calibration kit.


old pic with Holley carb, coming along nicely still lots of little things to do. Hopefully I will drop it into the lake in the next 2 weeks. Still need to buy a boat hoist also....
 
#21 · (Edited)
you were right about that exhaust tube into the outdrive, I'm not sure if it was just the flapper valve gaskets being all messed up or the amount of zebra muscles that blew out but it runs great now. After getting the boat to run properly I figured I'd throw a marine approved carb on there for safety because there will be a small child on board from time to time. We shall see in 1-2 weeks when I put it in the water, I'm wiring up the radio, sub and speakers right now.

I bought the boat from a guy who used it on Lake St. Clair and had no clue how the out drive got so full of those damn shells. Nasty little boogers...
 
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