225 EFI Mod question

[Bkeenom]

I have a 1998 225 EFI that I am beginning to do modifications on. It is currently stock. Plans are 250XB fuel ECU, 300 Promax ignition ECU, 4 butterfly intake, Heads and exhaust tuner. I currently have the intake, fuel computer and heads and am still looking for the other two. I have a couple of questions:

My replacement heads are 250XB from a 2001 model year. What modifications need to be done to the heads? What gaskets will I need afterward?

What exhaust tuner will work best with these modifications?

Need a 300 Promax ECU

[Go Time]

The heads don't have gaskets, they have orings, need the correct oring set for the heads you use. most 3.0L heads come 60CC and 62CC stock. No mods needed, just find a set of 60 CC heads. The only aftermarket exhaust tuner I've seen for the 3.0L is the MAD EFI tuner (Taylor Marine). Not sure that all the mods will do much, you are somewhat limited with the exhaust relieved 225 block. Most 250 and 300 blocks do not have the reliefs and port timing is different.

[PanRonnie]

hydrotec also has some stuff for your engine
pair of carbon reeds would do nice
they also have an exhaust tuner
http://www.shop.hydrotecmarine.com/c...?categoryId=11

[R.grover]

mad efi, hydro tec and dave bush racing all do tuners for the 3.0l merc. Id get some reeds from chris carson he is a vendor on here, great reeds and well priced. What boat are you running it on what rpms do you want to run you may want to get limiters lifted 300promax is stock 6400rpms simon motorsports can take emm to 6800 or 7000rpm. cdi can do it to.

[HStream1]

Just a FYI Mad EFI (Taylor Marine and machine) Are no longer in business.

[Bkeenom]

mad efi, hydro tec and dave bush racing all do tuners for the 3.0l merc. Id get some reeds from chris carson he is a vendor on here, great reeds and well priced. What boat are you running it on what rpms do you want to run you may want to get limiters lifted 300promax is stock 6400rpms simon motorsports can take emm to 6800 or 7000rpm. cdi can do it to.

It is on a 519 DVS. It is 20 foot 6 inches long. It currently runs 69 loaded. I have a new set of Chris Carson reeds that I am putting in when I change the intake. My last two items to locate are the Promax computer and a tuner. Not having much luck with the computer. Waiting for a call from Mr. Simon today to see what other options i have. Bob's machine shop sells a tuner for this block. Any experience with that one?

http://www.bobsmachine.com/Mercury-E...411-100000.htm

[PanRonnie]

think that would be a 2.5 tuner?
this should be a 3 liter
http://www.shop.hydrotecmarine.com/p...&categoryId=10

[Chaz]

Head's came in either 63cc ( C-10 ) casting number / or 73cc which is what your stock 225 heads are.
It's easy to tell the difference with just a ruler. Turn the head up side down and see how far it is from the deck to the chambers roof. the tight one's are aprox 1/8" shorter .
If you have the small chamber in your replacement set , there are two things left . And right around 2000-2001 they couldn't make up their mind whether to use the .095 ( late model ) or the .134 thick ( early ) O rings to seal the head at the combustion chamber .
The early heads used a banana shaped thermostat cover and a small copper/brass thermostat. Some of the heads were cast with the late model square block , but machined for the early covers . those can be easily machined to use the late model high flow thermostat and cover....

No need in buying an aftermarket tuner . You can do like Simon has / had on his web site. Drill a couple 5/8 th's holes in the bottom of the can . It will be fairly quiet at idle , yet be fairly aggressive once it comes out of the water .
Ohh yea , the tuner .. cut the inner can close to the casting mark . It wont burn the paint off the mid or burn the adapter gasket out ..
A mild motor will never need it , but you can gut the casting flash while your gasket matching the rest of it ... you'll have everything that is offered out there as of now ..

[Bkeenom]

Thanks Chaz for the really great info. I have a set of c10 heads from a 2001 250 xb. At 63cc would it be worth it to have them cut? From all I have read I don't want to go past 61cc. Would the 2cc be a large gain in performance? Also found a 250xb ignition. Would this be close to the 300 promax ecu performance? Would rather hold out for the 300 if it will make some difference. I also assume I should not put the heads on until I have both computers. Correct?

[Bkeenom]

Actually c11 heads. Not sure about these.

[Go Time]

If you looking for tighter heads 300X heads C16 are 60CC (except for the A20) and A20 and earlier are 62CC. They all use the large thermo.

[Chaz]

Thanks Chaz for the really great info. I have a set of c10 heads from a 2001 250 xb. At 63cc would it be worth it to have them cut? From all I have read I don't want to go past 61cc. Would the 2cc be a large gain in performance? Also found a 250xb ignition. Would this be close to the 300 promax ecu performance? Would rather hold out for the 300 if it will make some difference. I also assume I should not put the heads on until I have both computers. Correct?

A couple months ago , I had a guy with a box stock 225 efi ( late model Motorola) trade in a flywheel , inner can , 6 pedal rubber reed blocks and a set of 73 cc heads .

He took home a 13 lb flywheel , cut and cleaned out can like the one above , striped , flattened and tumble polished reed blocks with shortened stops and Carson reeds. He wanted to run 89 to 91 octane fuel , so I did a set of 65 cc heads for him .
He put just that stuff on his open fisherman boat . He called me about a week later and said it was 7 mph faster than it was before.
The whole deal with the 300 ign is it has a coupe more degree's of WOT timing which helps it accelerate harder and a little higher secondary rev limiter.
The idea of a 250 fuel box is these things run blubbery fat , so the lower HP fuel curve actually clean's some of that up . It also has the soft limiter which starts dumping extra fuel back in (nice right ) at high RPM . I never really saw much gain from the computer thing , the porting is so mild , that they quit pulling way before the "benefits" show up ...

Reed blocks look like this ...




The 73 and 63cc heads have a pretty wide chamber ...



Anything less than 65 cc I like to just weld up the chambers and mill them back out to whatever size we're lookin for .



This set is pretty tight but works well with a big exhaust port ..

[cali kid]

A couple months ago , I had a guy with a box stock 225 efi ( late model Motorola) trade in a flywheel , inner can , 6 pedal rubber reed blocks and a set of 73 cc heads .

He took home a 13 lb flywheel , cut and cleaned out can like the one above , striped , flattened and tumble polished reed blocks with shortened stops and Carson reeds. He wanted to run 89 to 91 octane fuel , so I did a set of 65 cc heads for him .
He put just that stuff on his open fisherman boat . He called me about a week later and said it was 7 mph faster than it was before.
The whole deal with the 300 ign is it has a coupe more degree's of WOT timing which helps it accelerate harder and a little higher secondary rev limiter.
The idea of a 250 fuel box is these things run blubbery fat , so the lower HP fuel curve actually clean's some of that up . It also has the soft limiter which starts dumping extra fuel back in (nice right ) at high RPM . I never really saw much gain from the computer thing , the porting is so mild , that they quit pulling way before the "benefits" show up ...

Reed blocks look like this ...




The 73 and 63cc heads have a pretty wide chamber ...



Anything less than 65 cc I like to just weld up the chambers and mill them back out to whatever size we're lookin for .



This set is pretty tight but works well with a big exhaust port ..

How do you strip the reeds? They look great. Have you tried any CC 3 petal reeds? Really nice looking work.
Randy

[Bkeenom]

Looks like I will have my old Ranger going 105 and no time. According to Chris and the three paddle reeds don't work so well on the EFI engines. They are better on the Optimax.

[Chaz]

How do you strip the reeds? They look great. Have you tried any CC 3 petal reeds? Really nice looking work.
Randy

Mr. Carson taught me how to to do them . He has quite a bit of money , time and effort involved in the reed business . It's not my place to say . However I'm sure he would share the procedure with you , or charge the going rate to prep a set of blocks if you don't feel comfortable doing it on your own . Very good guy to do business with ...

I thought we covered the three leaf deal last week ...