1999 OX66 Hydro tec Kits

[EMC 2870]

It has been a while since I have been here. I have two 1999 OX66 225 engines. One has actually been rebuilt by Hydro tec. I am looking for more power for my boat. I have been looking at their "Phase kits" but there is very little information on actual gains. Both of my motors run to 5500 RPM with no issue on a tuned 19" SWS prop. Compression is 120 +/- a pound on all 12 cylinders. I think my blocks are good for an upgrade. My question, has anyone used their kits on OX66s on a heavy boat and what gains did you get? Did you lose something on the bottom to gain top? Higher octane fuel requirements? Drawbacks?

Any info is helpful

[Greg G]

How heavy a boat? On the correct hulls the phase kits have been proven again and again. What type of boat do you have? How long are your mids? Can you get high test fuel on the water where you boat?

[EMC 2870]

How heavy a boat? On the correct hulls the phase kits have been proven again and again. What type of boat do you have? How long are your mids? Can you get high test fuel on the water where you boat?

Its a 2870 Pursuit CC. On the trailer full of fuel and water I am about 8700 lbs on the cat scale. I can get Rec 90 on the water but can have anything delivered to the boat, or I can caddie. Octane is not an issue unless I need AV gas. My Motors are 25 inch.

[Greg G]

Its a 2870 Pursuit CC. On the trailer full of fuel and water I am about 8700 lbs on the cat scale. I can get Rec 90 on the water but can have anything delivered to the boat, or I can caddie. Octane is not an issue unless I need AV gas. My Motors are 25 inch.

Wrong application. Go find yourself a pair of clean HPDI 300's and upgrade that way. 25" HPDI's are everywhere and burn 87. Good luck.

[Merc 2.5]

Ya 300 would b better route if funding available, the ox66 , they have built sum mean ones round here. Issue with urs is all the weight , if u do mods and raise comp ,, u take bigger chance of detonation and such ,, can it b done yes it can , but if u do go the build route , make sure ur spinning the motas least 6k rpm. When u lug em with lots weight and over sized prop it will kill em relatively quick

[EMC 2870]

Understood. Thank you for the advice. Right now it will run 52 at 5500 rpm loaded or unloaded with a set of nicely worked 19" SWS props. I could probably get some more speed with 21s but I really like the way she jumps out of the water.

[Merc 2.5]

Understood. Thank you for the advice. Right now it will run 52 at 5500 rpm loaded or unloaded with a set of nicely worked 19" SWS props. I could probably get some more speed with 21s but I really like the way she jumps out of the water.

What I'm saying is ur lugging the motors a little now , if u had a 18 or work ur 19s to 18 u will get the rpm u need and wont lose speed and take off b even better

[EMC 2870]

What I'm saying is ur lugging the motors a little now , if u had a 18 or work ur 19s to 18 u will get the rpm u need and wont lose speed and take off b even better

As currently set up, 5500 is max RPM per the manual. I thought because I can get to it fully loaded with 1400 lbs of fuel, 200 lbs of ice and four fat dudes, I am propped Ok. Low fuel no ice and just me, I stay at 5500. I dont know if I have a rev limiter, but power drops off at 5600 no matter the load.

So your saying I can get over 5500 and be ok the way its set up now?

[Merc 2.5]

Well maybe I'm just way off on this but I thought the ox66 could turn sum better rpm. Manual for 200 2.5 merc is 5500 -5800 I believe , but they live a gud life at 7k ,, need someone with that experience to chime in for ur mota , u sure it not 5500-5800 or 6000rpm. Should b a low and high range , by manual meaning no lower and no higher than 2 posted #s

[EMC 2870]

Manual says 5200-5500

I am sure it could spin more, but it pulls like hell to 5500 and drops off after that.

I am more of a car guy. I think props like the converter (prop slip) Transmission and rear gear. I have the prop set up to bite at 3000 rpm (like a high stall converter) and to get to max rated RPM fully loaded. Its like a car with a 3000 stall converter 4.10 rear end, Hits max rpm while racing, but rev limiter keeps it in check when playing around.

[EMC 2870]

Before I had my props tuned, the would bite at about 2200 rmps which really really hurt my hole shot. Adding ventilation really woke up the hole shot. The 400 rpm difference doesn't seem like a lot but really put it into the power band of the motors.