Tuning Mercury 2.4 Black max, what is worth while?

[Roos]

Hi,

I just picked up a Mercury Black Max 2.4 liter engine from 1985 (according to it's serial number).
My guess is that engine is stock, but I really have no idea.

I ran a compression test on it and it read between 129 and 132 psi on all 6 cylinders. I think all on starboard side had 129-130 and all on port side read 131-132.

I will run this on a 17-ft bass-boat-like off-shore racing boat.

I used to run a 90 hp mercury (2001) on this boat and finally hit 56 mph after extensive tweaking.

Since the new motor will have plenty of more power I guess the power-output won't really be an issue.
I will go fast enough anyways.

Though I would like to get as much power/performance out of this engine as possible without significantly increasing the risk of damaging the engine.

What I am considering:
Shaving heads, or are compression good enough? (I live in Sweden and over here we get 95 or 98 octane gas).

Boysesen reeds, do they really do any good?
Velocity stacks, same as above?

Engine louvers, don't wanna spend to much so new cowling is not considered, but engine louvers should help it breath? Right?

I have a low water pickup (transom mounted), would I still need a nose cone for stability?

Solid mounts? I'll use Uflex drake hydraulic steering.

Anything else that should be done?

Thanks,
Mike

[j_martin]

Black Max means big honkin' black thingie, and that's about all it says.

2.4 L V6 stock motors go all the way from 135 to about 250 HP. The biggest differences are major things in the reeds, and ports.

Likely, yours is a vertical reed engine which limits peak RPM to a little over 6000.

Increasing compression to about 150 will help a little.
Throwing away the "advance module" and timing it right will give you a bit at the top.
a shorter (200) tuner might give you a bit at the top.
Setting jetting by reading the piston tops might help bit.
Fiberglass reeds will help idle, and be more digestible if they fail. I use Chris Carson reeds.
That boat will kill you without solid mounts on a V6.

A stock 150 TOP out of the crate is about 135HP at the prop. A Stock XR4 out of the crate is about 162 at the prop.

Likely your biggest need will be testosterone.

[Markus]

Hey, good to see that you are back!

You can pump up compression to something like 145-148 psi with Swedish 98 RON gas. Btw, always run 98 in that engine, as it is ethanol free as long as you stay away from Shell.

Louvres will make your powerhead wet with salt water, and you don't want that.

Don't bother with velocity stacks.

Fiber glass reeds will make an insignificant difference in performance, but will not create the damage that a steel reed does if it breaks and is ingested.

You definitely want solid mounts.

With a transom-mounted pick-up you may get away without a nose cone, so you should at least try.

A T-17 with a 2.4 liter Mercury on the transom will be a handful to drive in any case, so don't do anything to the engine at this stage.

I have the big drum cleaver that you need...

[Roos]

J_martin, thanks, I know... I just somehow managed to miss the part about it being a 200 hp.

Ok, I think I might be able to get a hold of reeds and mounts locally (from HaHa, MarkusH... know if he's still "in the game"?).

Yeah, I finally tired of having the boat laying around and just happened to find a 200 hp black max for a good price in kungsbacka! (About 10-15 miles from home..)

How will the engine run with 98 RON gas and 129-132 psi compression? Do I need to do anything with the timing or needle to run well?
I might leave it at its current compression since I probably will have enough power.

Once the boat is ready, maybe early July, I would love to go out testing props with you again.
Still have the Spinelli DR4 which was the fastest out of 8(?) props with the last engine. Might have too much nose-lift now?

Have you gotten a new boat yet? =)

Thanks a lot!
Mike

[Markus]

Ok, I think I might be able to get a hold of reeds and mounts locally (from HaHa, Markus... know if he's still "in the game"?).

He is still around.

How will the engine run with 98 RON gas and 129-132 psi compression? Do I need to do anything with the timing or needle to run well?

Don't need to do anything.

Once the boat is ready, maybe early July, I would love to go out testing props with you again.
Still have the Spinelli DR4 which was the fastest out of 8(?) props with the last engine. Might have too much nose-lift now?

The DR4 does not give a whole lot of bow lift, but I think you will need stern lift now...

Looking forward to some prop testing...

[R.I.P.]

I have a 86 200 black max and run it around 7k rpm all day. Its just the mids on the fishing outboards that are bad . Last week the steering/swivel arm broke and it is made of cast . it ejected me out of the boat (only going 30 or so ) check often be carefull. Another time I was running full throttle and cut off the gas the motor came out of the water lost all control of the boat it was a missle . The fishing mids three piston ones are dangerous for high speeds. Be careful ..

[Roos]

I've finally been able to do some test runs and we came across a problem with the cooling. First time out we didn't have any low water p-u on and then figured that was the problem. We run the motor with propshaft about 1/2 inch below the pad. I blocked off the top 4 holes on the LU, didn't help.
I then found time to get the LU to a mechanic friend and we installed a nipple for the transom mounted low water p-u on the hull. This helped but we still have issues.

Running 20-25 mph the engine seems almost fine (maybe a little hot) at 150-170 degrees.
Idle gets to 185 and sometime even above that which mean I have to shut her off.
WOT makes the temperature start creeping up and once we hit 190 I pulled off on the throttle.
No damage to the motor from what I can tell and there is always some stream of water out the tell-tale.

I have (tried to) installed a water pressure gauge though I cannot locate a good place to put the hose on the motor. I have read that some black max have a plug behind the fly-wheel on top of the motor, ours doesn't. I then read that some have a hose going from the top of the motor to the poppet valve, ours doesn't. Since we have both alarm and temp-sender in the tops there is no room to fit it.
So far I have T-ed in on the line from the thermostats, though I don't know if this does any good, since I get a very low reading.

The PSI at idle are about 1 and at WOT gets to maybe 5-6. This is far too little from what I understand.

I have ordered a new impeller kit and this is my next step. Since the thermostats are closed at start up and starts to open at maybe 150 they should be fine? I inspected the poppet valve. Though I don't know what it should look like I found no apparent damage and decided that it probably worked since I have a cooling problem at low RPM:s as well.

Any suggestions except impeller and debris stuck in the lines are welcome. (Confirmation that is should be any of the mentioned are also welcome. =) ).

When we pushed the engine to WOT and maybe kept going for 8 seconds (then the temp reached 185-190 and we eased off) we reached 60.2 kts (69 mph) and it was obvious there was more coming.
Though I see the point in that there is probably going to be a need for testosterone... =)

I have decided to change to solid mounts as I have now found out that the ones on there were rubber. The engine "wiggles" quite a bit from side to side in its mounts.
From what I can tell it looks like the lower mount on the before mentioned swivel arm is also wiggling...
How can I check to see if it is in good or bad condition and what might one do to fix it?

Also any suggestions of how one would go about changing the mounts are very welcome. I have a seloc manual and a motor-lift...

Thanks
Mike

[ChrisCarsonMarine]

In 1985 the only 2.4 fishing motor made was a 200,and it has horizontal reeds,(1983 on).the smaller motors were still 2.0 liter,I think.Mounts,reeds,mill heads for 145 lbs.compression,and make sure the carbs main jets have been updated...they came with 076/078 back then,merc put out a kit and service bulletin upping them to 080/082.Remember the fuel/air flows across a horizontal reed merc,ie. the carb in front of cyl # 1 feeds cyl#2 and so forth.Hold on and wear your life jacket,have a chase boat,Chris

[Markus]

I've finally been able to do some test runs and we came across a problem with the cooling.

Any suggestions except impeller and debris stuck in the lines are welcome. (Confirmation that is should be any of the mentioned are also welcome. =) ).

With a transom-mounted pick-up, you should have enough water that you wouldn't even need an impeller to keep the engine cool at speed. My guess would be one of the following:


a) the tube from the lower unit does not line up properly with the tube in the mid-section, so the water leaks out before reaching the powerhead. If that is true, you would notice on the hose


b) you have some serious debris somewhere in the cooling system


c) your transom-mounted picked is rigged on the pressure side of the impeller, so the impeller sends your cooling water out the pick-up instead of up the engine

Also any suggestions of how one would go about changing the mounts are very welcome. I have a seloc manual and a motor-lift...

You will need to lift off the powerhead, which requires a loosening screws which may not have been loosened since the engine was built. So, plenty of patience, 5-56, and probably some heat as well will be required.


Also, you will need a new powerhead gasket. If the 2.5 260 uses the same gasket, I am pretty sure I have a few.


Btw, I have a bunch of impellers/water pump kits as well, I believe.


Finally, I am happy to take a look if you come by...

[donmac]

you need a check valve in the transom pickup hose to stop losing pump water out of the transom pickup!and preferably one you can remove a cap to clean debris out of it!

[Roos]

a) the tube from the lower unit does not line up properly with the tube in the mid-section, so the water leaks out before reaching the powerhead. If that is true, you would notice on the hose

That is very possible since I removed the lower unit to drill for the transom pick up and did have a hassle to get it to line up with the gear-shifting shaft (forgot the name). Can't say I paid to much attention to the impeller tube.

How would I notice on the hose?

b) you have some serious debris somewhere in the cooling system

This could be it. First time out (without the low water p/u) I plugged the top 4 holes on the lower unit with screws and plastic plugs (as I did on the 90 hp merc). When removing these a couple of the plastic plugs broke. I got these out of the water chamber, but I don't know for sure if any bits of plastic might have broken loose earilier and traveled up the tube. Might be something like that being stuck somewhere.

c) your transom-mounted picked is rigged on the pressure side of the impeller, so the impeller sends your cooling water out the pick-up instead of up the engine

I am guessing this would mean above the impeller? It is mounted below the impeller, just above the lower anti-cavitation plate, on the starboard-side.
That puts it just below the opening in the bottom of the impeller housing. That was basically the only place that I felt comfortable drilling, thus the choice.

When connecting the motor to a hose using the normal rubber pads over the intake holes on the gearbox it starts flowing water out the transom mounted pickup. When the motor starts it stops flowing water out the pick-up.

You will need to lift off the powerhead, which requires a loosening screws which may not have been loosened since the engine was built. So, plenty of patience, 5-56, and probably some heat as well will be required.

Also, you will need a new powerhead gasket. If the 2.5 260 uses the same gasket, I am pretty sure I have a few.

Btw, I have a bunch of impellers/water pump kits as well, I believe.

Finally, I am happy to take a look if you come by...

"Luckily" the previous owner had a similiar problem with his cooling and left the engine with a local marine that finally did pull the power head to clean out debris which solved the problem. This means the power head has been pulled this winter or maybe last summer. So the screws shouldn't require to much patience.

Okay. How can I find out about the gasket? Anyone?
Otherwise I guess I will have to get one.

I'll give it a shot and if I can't figure it out I am very greatful if I can swing by! =)
When I get this solved it is time for a new prop-test. The spinelli DR4 still seems to work fine though as it easily reaches 60 kts. Don't know how much faster I need to go...

I ordered solid mounts yesterday that will probably arrive in about 2 weeks.

Thanks for the suggestion about a check-valve. Worked great without it on the 90-hp mercury, but I will take it in to consideration if I don't get this sorted by replacing impeller and lining up the tube.

[Markus]

How would I notice on the hose?

A lot of water would come out from that area pretty much immediately.

Thanks for the suggestion about a check-valve. Worked great without it on the 90-hp mercury, but I will take it in to consideration if I don't get this sorted by replacing impeller and lining up the tube.

If your water pickup is on the suction side of the impeller, you don't need a check valve.

[Roos]

A lot of water would come out from that area pretty much immediately.

What is "that area"?
The tube is from the impeller housing and up threw the mid-section to the block. It would be impossible for the water to get out between the lower unit and mid section.
I didn't look at this specifically and don't really know how everything is built but I guess water flowing out the tube from the impeller and not going upward would find its way to the exhaust channel and go out the exhaust at the propeller hub?

There sure is a lot of water flowing down there, but at the same time water that doesn't get in the water pickup-holes start spraying in all directions so I can't say I am sure that the water goes that way.

Wouldn't a lot of water be flowing out the exhaust down there always?

Sorry for being slow in understanding how to check for this but I rather make sure I do it the right way.


On a different topic. Can you recommend a good hopefully not outrageously expensive oil? And where to get it.

I have thus far found semi-synthetic high performance penzoil, which I at least guess is better than statoil semi-synthetic? Haven't really been searching for it.

Thanks again!

[Markus]

What is "that area"?
The tube is from the impeller housing and up threw the mid-section to the block. It would be impossible for the water to get out between the lower unit and mid section.

No, that's where it would come out. It comes out of the impeller housing, but then runs down on the impeller housing and out. You would notice a timing difference if nothing else compared to water having to go up into the powerhead before it comes down the mid and out.

On a different topic. Can you recommend a good hopefully not outrageously expensive oil? And where to get it.

I have thus far found semi-synthetic high performance penzoil, which I at least guess is better than statoil semi-synthetic? Haven't really been searching for it.

Thanks again!

I have enough Pennzoil 100% Synthetic on the shelf to keep you going for several years. Just let me know how much you need.

[donmac]

you need the check valve if your plumbed directly to the adapter from the transom, definately a no if your feeding the waterpump from the transom pickup,too restrictive!