2.5 fishing boat engine

[summerfordstv]

Hi all ..Looking at making a healthy 2.5 steel bore to run on premium pump gas...I have purchased some 50 series rods, Would like to turn rpm to around 8000 rpm ...The boat is a very efficient sst 140 tunnel and i want the 2.5 to use as a CLUB HACK.....What brand of pistons can i buy that will be reliable????Reeds, Will i get away with 4/5 petals ????? I have some 245 hp carbs.Will they be suitable ???? Will an oiler crank to the job ???? Any advise will be greatly appreciated.. Regards Chris:cool:

[Jay Smith]

Chris ,
If your going to be punishing the motor and turning 8000 + for extended time I would use the Wizard forged racing piston , its a popular choice here in the states in Drag , F1 and sand bar racing where high rpms is the norm...

I also use the TDR ( Tony Doukas Racing ) reeds, my customers rave about their performance as well as longevity in high rpm as well as recreational applications and are available in many different weaves as wells a thicknesses...

The oiler crank is OK, I would opt for the more durable High Performance connecting rod bearings.

I also epoxy up the #2 oiler gear cavity to dissapate the volume as # 2 is always a lazy bore due to its extra volume causing lazy air speed..

Shave off .050" from the reed side of the front case half that will pick up a gang of bottom and mid range torque. ( you may need to lower the reed cage boss where the attachment 1/4" X 20 screw boss is as well as where the reed screws may contact the block's front )

Cut heads to be suitable to the octane thats available to you. In the states I think we have different methods of octane rating as do Europe and other countries.Just be sure you have enough octane to support the compression your creating with tighter heads. I find that 145 lbs cranking compression @ sea level with a WOT timing setting of 25* on the highest timing hole is safe..

GOODAY mate,
Jay

[summerfordstv]

Hey, thanks Jay... I have used dukes reeds on my OMCs....The reed deal worked well on the omcs also...I will do the changes as directed...Port timing any ideas on height ...Also those carbs???? Im not one bit familiar with those merc carbs.....I have many sets....Including those 245 hp ones with that economy bleeders fitted...Can you make those things work OK ????? thanks from OZ

[David]

OZ uses RON. North America uses (RON+MON)/2, which gives a lower advertised number.

[gmjim]

our 98 is US 93, from my understanding.

[Germansaleen]

In Europe 98-octane gasoline is common and even 100 to 102-octane is readily available at the pumps, but this octane nomenclature is misleading to Americans as foreign octane ratings are derived entirely differently from your us pump gas... So, like every other measurement system it seems that everyone else uses a different scale than we do, but unlike most other instances where we have had the good sense to create different units of measure in this case we all use the same name...
Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

We have Shell V power 100 RON and Aral Ultimate 102 RON :smiletest: but for $ 4.80 a Gallon:nonod:
and you guys catch up in price with us..... , i checked the prices in my old hometown coralsprings/FL today and its now $3.30 to $3.90 for regular , i did pay $1.60 7 years ago in Fl at the pump.