HELP! Mercury 3.0L block differences

[Mxdude91]

So I have a 98 Mercury 225 carb 0G607475,one of the cylinders ran lean because of a problem with a fuel/water separator. Connecting rod went through the block...pulled it down and found the other 5 cylinders were fine and the crank was good 2. So I found another 3.0L block... 0T652491 believe is a 250xb block.i had to drill and tap the bleed line fittings to match the old engine...got it back together and it seems to idle low and dies when under load...Any underlying problems with block swap?

[Mxdude91]

8859811c15 is the new block serial number
The original block serial number is 8859811a19

[Mxdude91]

120 psi compression and crank sensor adjusted to .040” air gap and resistance of the crank sensor was in spec.engone ran good except it was running lean and surging at wide open throttle I fixed that problem but not quite fast enough before it had already damaged the engine..I’m curious if the block has any differences that would effect ignition timing

[Chaz]

Blocks : Either early or late , throw the opti-pop's in with the late.
If your twin pancakes and its sensors etc. bolt on it's an early. Likewise for the Motorolla on the starboard side.

Bleed lines : The factory has tried every conceivable arrangement and location over the years, I don't think any particular one works better or worse than the other.

Timing : Early model uses a slotted plate to mount the TPS .4 to 4.5 V on some 4.5 to .4 Volts on others ( carb vs EFI read backwards from each other )

Idle 4* ATDC WFO 25-26

Late model : has a non-adjustable linkage bar. ( they don't trust us )
I made mine adjustable. ( 28 with 93+ @ 150 psi )

Pulse Pump : Keep a fresh kit installed ... 4 psi < Lean surge ???
Personally, I like those Carter electric pumps. Bout $75.00 @ NAPA . Throw the ####### pulse pump away , make the electric pump come on with the key , no more fuel delivery issues !!!!!

Carbs : Make sure all the circuits are clean. They feed at partial throttle openings thru a series of three small holes that progressively uncover as you open the throttle. Even though they are the "idle and tip in" they never stop flowing. If they are partially plugged, it will be lean thru out the entire fuel curve.

Reed Plate Gasket : Pretty basic, but make sure you have the right one. Some look dangerously close to leaking while others can block oil holes ( 300x and Opti's )

[Mxdude91]

Blocks : Either early or late , throw the opti-pop's in with the late.
If your twin pancakes and its sensors etc. bolt on it's an early. Likewise for the Motorolla on the starboard side.

Bleed lines : The factory has tried every conceivable arrangement and location over the years, I don't think any particular one works better or worse than the other.

Timing : Early model uses a slotted plate to mount the TPS .4 to 4.5 V on some 4.5 to .4 Volts on others ( carb vs EFI read backwards from each other )

Idle 4* ATDC WFO 25-26

Late model : has a non-adjustable linkage bar. ( they don't trust us )
I made mine adjustable. ( 28 with 93+ @ 150 psi )

Pulse Pump : Keep a fresh kit installed ... 4 psi < Lean surge ???
Personally, I like those Carter electric pumps. Bout $75.00 @ NAPA . Throw the ####### pulse pump away , make the electric pump come on with the key , no more fuel delivery issues !!!!!

Carbs : Make sure all the circuits are clean. They feed at partial throttle openings thru a series of three small holes that progressively uncover as you open the throttle. Even though they are the "idle and tip in" they never stop flowing. If they are partially plugged, it will be lean thru out the entire fuel curve.

Reed Plate Gasket : Pretty basic, but make sure you have the right one. Some look dangerously close to leaking while others can block oil holes ( 300x and Opti's )

Chaz,thank you for your reply,not sure if I understand what twin pancakes are? But are there differences in block like porting and such.because I’m trying to figure out how I went from having pretty damn good running engine to now after the rebuild it idles low and dies on the trailer in the water when I’m in gear. New stator tps is adjusted with volt meter and engine temp sensor/crank sensor ohm good and are properly adjusted at .035” . Pulse pump was rebuilt in the fall chasing the lean condition.

[vnemous]

Twin pancakes is referring to the two computers on the back vrs the one on the side of newer motors. Other than that he's speaking Greek

[Dave S]

If your first 3.0 build small rubber blocks/check valves on reed block gasket fall out could mess with idle speed.... Just a thought.

[Mxdude91]

If your first 3.0 build small rubber blocks/check valves on reed block gasket fall out could mess with idle speed.... Just a thought.

Thanks Dave,I removed the little rubber square pieces one at a time and transferred them to the new block right before reinstalling the carburetors and reeds

[Mxdude91]

Twin pancakes is referring to the two computers on the back vrs the one on the side of newer motors. Other than that he's speaking Greek

Haha, I have a single computer that sits between the heads.im assuming that because it is carbs

[vnemous]

Haha, I have a single computer that sits between the heads.im assuming that because it is carbs

Yes no fuel computer missed the part of it being carbed but easily changed over to fuel injection

[Chaz]

Chaz,thank you for your reply,not sure if I understand what twin pancakes are? But are there differences in block like porting and such.because I’m trying to figure out how I went from having pretty damn good running engine to now after the rebuild it idles low and dies on the trailer in the water when I’m in gear. New stator tps is adjusted with volt meter and engine temp sensor/crank sensor ohm good and are properly adjusted at .035” . Pulse pump was rebuilt in the fall chasing the lean condition.

The early blocks : 225 - 300 PM all the ones I measured ... same

New stator .... hummmm Pppffftttttt did you ohm check it
Just use your timing light make sure all 6 are firing . While your at it, check the timing. While your still at it .. mark and check the other 5 holes ..

Start enrichment: make sure that little valve on the side of cab is opening , but more important ... closing when it warms up.

Dave S ... LOL Little rubber buggy baby bumpers are greek to me ... I weld the path shut and move the bleed hole, clip the front, move the screw clearance slots, make my own billet reed blocks ... aww nevermind, it's lotz easier to buy a used 300 X

[Dave S]

Chaz.... but more fun to make Chips with a mill......I am novice with 3.0s.... but the Rubber baby things.....if ya don't know I think leaving them out could cause running issues.... Had a 3.0 never could get it to run.... next time 2.4 ingnition ..... I can get those to start.....

[Mxdude91]

The early blocks : 225 - 300 PM all the ones I measured ... same

New stator .... hummmm Pppffftttttt did you ohm check it
Just use your timing light make sure all 6 are firing . While your at it, check the timing. While your still at it .. mark and check the other 5 holes ..

Start enrichment: make sure that little valve on the side of cab is opening , but more important ... closing when it warms up.

Dave S ... LOL Little rubber buggy baby bumpers are greek to me ... I weld the path shut and move the bleed hole, clip the front, move the screw clearance slots, make my own billet reed blocks ... aww nevermind, it's lotz easier to buy a used 300 X

Chaz,
SORRY FOR BEING SO LONG WINDED

I installed a new Mercury OEM Stator last fall after finding the originial stator did not ohm well,I just rechecked it and all 6 bobbins were 1100 ohms

I had a Mercury OEM Engine temp sensor so I threw it on for ****s and giggles, they both had the same resistance between the brown wires and open circuit between brown wires and ground

Throttle Postition sensor says 3.8V at idle and .95V at WOT...this is backwards to the manual but I have checked this several times when the engine was running correctly and it has always read that way.

I have checked resistance for all the grounds on the ignition coils to the negative cable running to the battery, all had 0.2 ohms, checked the resistance running from the stator ground and the same..

I indexed the flywheel at TDC for each cylinder and marked it on flywheel.the engine was cold and the timing was advanced, once the engine ran for a bit it seemed to be firing on time at idle...a bit jittery and I'm not really experienced with a timing light and especially a 2 stroke and checking timing...but I removed the throttle cable and was able to accelerate the engine and it would get rid of the jitteriness of the timing and it would advance and retard the timing smoothly if you could further discuss this that would be nice.

all cylinder lit up the timing light and I checked to make sure it wasn't erratic on all 6, also pulled out the spark gap tester and each cylinder could jump a 7/16" air gap.

The crank sensor resistance is in spec and the air gap is set to .35 "

All 6 Carbs seem to have good fuel flow based off the intake of the carbs having fuel/oil slightly puddling
primer bulb is tight

The carbs have been cleaned 3 times in the last year..only once have I noticed a difference in how the engine ran..always set the air mixture screws to 2.5 turns out.

All New Champion Ql77cc gapped to .35"

Reed block gasket is new and all the 8mm bolts are tight

used loctite gasket maker in-between the block and intake/bottom end.

all the crankshaft sealing rings are installed , one of the sealing ring groove on the used block was slightly grooved, I was told by Lee Sanderson at Sanderson Marine(where I got the block) it would be fine I also read in the service manual it would be okay as long as the crankshaft spun freely.Causing any issues?

Fuel Pulse pump rebuilt 2 months ago(maintenance) I run 50:1 premix and have pulse check valve removed and sealed with plug, oil injection pump removed and plugged as well.


(On the Muffs) the engine seems to idle lower and be quieter than normal, has long crank but once running will run until I cut it off.

(In the water) the engine is defiantly quieter and still long cranks and Huckle bucks when put in gear, when given throttle it falls on its face and dies

THE ENGINE RAN AMAZING EXCEPT FOR THE LEAN CONDITION(FUEL RESTRICTION) I RAN INTO RIGHT BEFORE THE ENGINE BLEW(#1 PISTON SEIZED IN THE CYLINDER AND THE CONNECTING ROD RIPPED OFF THE PISTON AND DAMAGED THE SLEEVE.​All I did was replace the block(match the bleed system to the original)Repair the fuel restriction keeping the primer bulb from getting tight, replace all the bearings on the crank and install new piston rings and replace the one connecting rod/pistion..all new gaskets.

[Mxdude91]

I haven't looked into the fuel enrichment system yet


Service manual I have been using for 2 years

http://www.hedges-uk.com/boat/Merc/o...nd%20Above.pdf

[Capt.Insane-o]

Shift interrupt switch?