My first 3.0 EFI

[Aaronhl]

This thread will be for the questions I have about my first 3.0L Merc EFI Outboard. I neglected service of the engine once I got it earlier this year only to instead run it hard a few times and burn down some cylinders...There's atleast one person that warned me to do some maintenance


I have the winter to learn as much as I can to fix the engine, been kinda intimidated by the EFI setup as my other Mercs are 2.5 carbs...


Powerhead
0G325775
1996 Outboard 225EFI


On a 20" Midsection
1B321430
2006 250 PROXS


Heres a pic of the engine and will posts questions as I have them

[Aaronhl]

Heres what happened a few weeks ago to #2 and #4, I have since took out the 2 bad pistons and removed the aluminum from the cylinders walls with acid, I am awaiting a 120 grit ball hone

The "rebuild" right now is hinging on a good compression test after I hone the two bad cylinders and put some pistons back in there. Looking at the scratches I know its not ideal but I kinda want to try to do this way first before I get the cyilders professionally done...

[Aaronhl]

First few questions


Where is the port side temp sensor?

Should I plug the wash out port so water doesnt constantly come out while running? Is that making it so my engine doesnt keep water in there to cool?

Which powerhead gasket do I use with this mid section?


Will be going through eveyrthing including injectors, replacing reeds, and testing the electronics

[rgsauger]

Also ask the fellows that know if you need to have the rubber flow diverters installed in your block before you put the heads back on. I know you do for a 2.4 and a 2.5 but I do not know about a 3.0

[Code Red]

Following. I'm trying to get my first set of 300 promaxes up and running (bought 1 blown), so I also have plenty of questions.

As for the diverters, I know I have them in my motors. Ill post some pics when the block gets back from the machine shop.

[Aaronhl]

First time I am hearing of diverters, I searched to see they are tubes to limit the flow of water around the cylinders... I havent seen them in my 2.5 and this 3.0 doesnt have them either
I'm concerned about making sure this 2006 250PROXS exhaust plate fits the right way on the 1996 powerhead. AND cools the engine like it should The person that put it on previously used a paper gasket with a bunch of silicone

[moparbarn]

Aaron, I would not use a ball hone on a ported cylinder- EVER!! They are notorious for losing & chipping balls on port edges. Little chunks of abrasive material can & will destroy an engine in short order. Easy to miss & difficult to clean out of the block. Old school straight stone hone on a ported cylinder, IMHO. I would have to think the flush plug needs to be in place for the cooling system to work properly.

[PanRonnie]

I added the later style and early style 3 cooling sadly the book of the older engine has no cooling route page
but the older would be similar as the 2.5 with the exception it wouuld only have holes next to the bottom cylinders
Now would it be necessary to add diverters !? i added some possible locations for partial blockage but don,t think it is necessary
so your cooling would come in next to cylinder number 6 towards the exhaust then flow around both cylinder walls upwards to the top then drop down over the heads and exit through the bottom hole entering the mid plate

The newer engine would have the same place entering the around the cylinder walls but stay on one side going up to the to and around to the bottom
At the bottom it would divert to the mid plate towards the poppet valve and second route in the cylinder head entering from the bottom going to the top where it reaches the thermostat
the thermostats probably have a bleed hole to bleed the air and start to open once the thermostat reaches desired temperature

[Aaronhl]

Aaron, I would not use a ball hone on a ported cylinder- EVER!! They are notorious for losing & chipping balls on port edges. Little chunks of abrasive material can & will destroy an engine in short order. Easy to miss & difficult to clean out of the block. Old school straight stone hone on a ported cylinder, IMHO. I would have to think the flush plug needs to be in place for the cooling system to work properly.

I was gonna buy the 3 piece stone hone however I saw in older threads the ball hone is better so you dont chip a stone??

[moparbarn]

You can chip a stone, if you catch a port edge with the end of the stone. Key is to buy one with long enough stones to bridge the ports at both ends of the travel. Ball hones are entering the ports & then getting dragged out across the edge of the port constantly. As long as the END of the stone hone doesn't enter the port, it is fairly rare to chip one. Also MUCH easier to check a stone for chipping than all those individual balls.....

[Aaronhl]

Got the ball "dingleberry" hone in the mail today, used it on the two bad cylinders, here are the results, gonna order some used ebay pistons, a cylinder head, new piston rings and o-rings well see what the compression looks like after that

[Chaz]

No port side head temp sender .. only starboard.

If you mean where a garden hose will screw into the rear snorkel , then yes it needs to have a plug screwed in.

They have superseded the base gasket's so many times, that they have settled on two. Either will work, the standard $26 dollar one and the $55 dollar hi-perf one (pro marine)
The only place it makes a difference is the gasket between the exhaust adapter plate and the can. Early model is green and the late model (like yours) is standard greyish black.

The early-early blocks didn't have water diverters. They added them later , you would be able to see half round places where a 5/16" x roughly 2" piece of solid rubber round stock would fit in.

It looks like you left the hone in one place and just let it go in circles. There needs to be a cross hatch that has a 30 to 45 degree pattern to it.
Some of those deeper scratch's / gouges looks like they have a raised burr on each side of the trench. If nothing else, hand sand the high spots down.
The low spots .. I call "oil retention ponds"
Even if it looks like a brand new penny, you need to measure each bore to make sure its still round. Top- bottom on the thrust face and top-bottom at 90*. 3.626-3.627 after that, it's wise to bore the block.
A real hone can apply pressure to the walls to straighten them out. Those springy thingy hones .. not so much. Ball hone, not at all.
Used, std. 3.0L pistons .. if they don't measure at least 3.617 on the thrust face just above the boost port window ... I won't use them.

What Moparbarn spoke about it somewhat true. An interrupted (ported) sleeve or "Keystone" as it's called thru-out the industry , says that the best way to hone sleeves with holes in them is with holders with two stones per holder across from each other and two guides arranged in the same fashion.
My powerhone uses AN style stones. The standard Sunnen AN stones work just fine. And there are times where the short "bottom pressure" stones are needed to straighten out a hole. I have never had a problem with one catching in a port.

After you wash the block 3 times and it's all ready to go ... wash it again ..

https://goodson.com/collections/sunn...-honing-stones

[FUJIMO]

...r u doing this with an assembled motor?...

[PanRonnie]

Still see a lot of grooves!
Might be an idea to just send the block to somebody to get it fixed
bristol Season is also over

[Chaz]

...r u doing this with an assembled motor?...

Now that you mention it ... I do see a crankshaft in there.

PanRonnie

Might be an idea to just send the block to somebody to get it fixed

Aaron, both these guys are right. The motor needs to come completely apart. Washed, measured with a dial bore gauge and then make some decisions on which direction to go.