Please help me get this motor running

[wiigelec]

Merc 3.0L two stroke 225 hp

When i picked up the boat last fall it wasn't running very good. it had sat for a year so i figured there were some fuel issues. it would run around 4500 rpm and 30mph WOT. cleaned and rebuilt carbs and replaced the fuel lines bulb and filters and rebuilt the pulse pump. now it will only idle for a bit then dies. it acts like the fuel pump isn't working. i can pump the bulb and get it to run for maybe 30 seconds. then it tries to fire but will only run for a few seconds. if i pump the bulb too much it will start dumping fuel out of the carbs.

i have run the following diagnostics:

compression - 70 ish on all cylinders with crappy HF gauge. i have a better gauge but need to charge the batteries. will check when the batteries are charged.
leak down - minimal loss on all cylinders up to 80 psi

link and sync
replaced fuel lines, primer bulb, filters
rebuilt pulse pump
clean (spray and poke with little brushes and dry with compressed air) and rebuilt carbs (needle and seat) and re-jetted for elevation 6000'

check spark with timing light and spark tester on all cylinders

calibrate TPS

also run off remote fuel tank same results

I'm thinking my next step is to get a clear fuel line between the inline filter and #1 carb to check for fuel flow. any other thoughts?

[David - WI]

Sounds like the pulse pump isn't pumping any fuel. If it's hooked up right you probably need to take it back apart?

[pcrussell50]

70 seems is a little low, even if all are the same, which as least that bit is good news. I have a cheap compression tester (the one they lend you for free from Autozone), and it read dead on the same as the one the marine mechanic who sold me my 2.4/200 said. Also, leak down at 80 psi? Why not 100 psi?

Report back when you get your results from the "better" gauge.

-Peter

[David - WI]

You can't use the cheap "car motor" guages... you need the Snap-On style where the Schrader
valve is in the tip of the hose (in the spark plug hole).

Four-stroke car motors have bigger cylinders, full-stroke compression cycle, bigger combustion chambers... so the volume of the hose on the gauge isn't such a huge factor.

[mercrazy]

Did you change needles and seats in carbs?

[wiigelec]

Did you change needles and seats in carbs?

yes oem rebuild kits

[XstreamVking]

Bore scope the cylinders if you can, rings may not be sealing due to being "coked" up or maybe damage to walls. 70 pounds is too low to run well. Could try mercs "power tune" cleaner in the plug holes. Trim it up, pull the plugs and pour in the power tune, replace plugs, let sit overnight and start it up. Need to run it at wot for a few minutes to blow out the crap after.

[wiigelec]

with the carbs off i pumped up the bulb and a little gas came out the fuel line but a lot of gas came out the exhaust. pulled the crankcase hose and pumped the bulb and gas came out. pulled the pump, plugged the outlet and blew in the inlet and air came out the impulse port. pulled the pump apart and i don’t think the rebuild kit came with the correct diaphragm as it has holes in it. put the old diaphragm back in and no more gas out the exhaust.

[XstreamVking]

Easy to get stuff backwards in those too..

[David - WI]

[wiigelec]

sneezing and smoking and oil from behind the electrical box

[David - WI]

What is that broken hose? A bleed line or oil line?

[wiigelec]

bleeder line

[Jim Speros]

On the fuel pump. OEM kit comes with or used to 2 options for the outside diaphragm . Some engine models mix oil from oil pump in that chamber and need the holes.

The early 3.0 had a long list of bulletins on bleed system. Many check valves. it can be hard to tell whats a check valve or a simple fitting by looking. It may be necessary you find a bleed diagram showing the check valve for your serial group engine. Then check each and every one. May be easiest to replace each hose one at a time.

[wiigelec]

i think there is something wrong with the computer. it only gets up to 1800 rpm now and acts like the firing sequence is out of sync. the TPS was way out of calibration when i checked it, now that it is calibrated correctly it won’t run right.