need more power

S

Shrek

Junior Member
I can't leave anything alone. Now that I know that my cc will do 44 knots with a full tank and two guys plus bait, beer, and fishing gear ... that does not feel fast enough. What are the potential drawbacks to putting something bigger than my 225 on the back.

like this
http://neworleans.craigslist.org/boa/2348085900.html

I'm not trying to reinvent the wheel here, and I don't want to try to turn this old off-white girl into something that she is not. That said, the weight of a 300 two-smoke is comparable to my 225. What kind of transom mods are we talking to make this happen and what kind of performance do you think I'm likely to see from a 75 hp increase?

Opinions gents? :beer:
 
50 is moving right along for a V-20. That 300 pro mag probably wouldn't be a good engine on a V as it is ap erformance engine that isn't meant to have al ong service life really. Also the 75 extra HP doesn't sound like much, but even on a new transom that would be pushing it. Most likely if your transom is in GOOD condition, a center knee brace would be more than enough to handle it.
 
Hopefully my old buddy Ridge Runner will come along and tell ya how he got 60+ from a 250 on a CC...had to tape my eyeballs in place when he opened her up!!...:clap:
 
If that motor ain't hurt, that thing won't last long they are good motors. You don't see many in 25" either. Ferm is right on about the transom. I would add that the rest of the hull be up to the task as well. While the 300 ProMax may not have the same service life as a 250EFI, they aren't that bad. Same 3.0L displacement and intake as the 250EFI with slightly higher port mapping, exhaust chest, tuner and different electronics. It was 2001 when Mercury started calling them the 300x and they changed the intake and used chrome bores (which require a re-ring @ 250 hrs). The 300 PM should put you into the high 60's IMO. I still don't know what will happen after 63 MPH. I would suggest you to ease into those speeds. It should get interesting.
The 20v does start to chine walk at 60 plus. It is a sickness.
BTW- That motor will use over 30GPH @ WOT.
 
I can run between 50 to 53mph on gps (wind dependent) with 4 guys and all required fishing gear,bait,trolling motor and ice for the day with a stand up top(enclosure) with just a 200E-Tec---it is a HO big block version--they say actually 218 at the prop. No need to go crazy--LOL.

Just a newer fuel effiecent model.:clap:
 

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i dont think Id mess with a good running motor just for speed but Im wanting a 175 on the 18 so I have no room to talk (even though that will be only when I repower anyways)

If you got the time and $$ to play go fur it...would like to see how it goes. :clap:
 
Thanks for the input guys. I'm not sure that I want to sink that kind of scratch into this boat yet ... But I'm tempted. My transom is good with double knee bracing in the center. Is this something that should go on a bracket or is this better on the transom itself? I'm gong to wait till I put the 225 on the jack plate next week (thanks Cap'n Pete) and see if I can get 55 with less motor in the water.

Ridgerunner, is there a thread detailing what you had to do to hit 60+?

On a related topic, is this the sort of thing where I should start thinking about a low water pick-up?
 
Not really a special thread on getting to 60. Just tried various setups and props with the bigger motor. It has a few more mph left in it but it is close to all it will do. Genie Aye has a killer combo that sips fuel.
My 250 EFI motor is on a 30" Stainless Marine bracket, motor is raised so the propshaft is 2" below the bottom of the boat. Any higher and the water pressure suffers. Spinning a 23 Tempest to 5800 rpm, lots of prop slip tells me there is more MPH to be had. However, if I load the boat with 4 guys loaded for fishing and a full load of fuel, livewell full my top speed is around 54 with the same prop only turning the motor 5500 rpm. Full T-top and big console.
 
@ RidgeRunner: I looked in your gallery last night and your boat looks fantastic. Sounds like it goes as good as it looks.

I'm putting the motor on a jack plate this week. Is there any reason for running a low water pickup if I do this? With your familiarity with this boat, what pitfalls should I look out for?

Also, after reading through the 50+ thread, it sounds like you have a significant familiarity with props. I'm turning a stainless 19p, brand unknown, the leading, trailing, and prop tips are a little banged up. Any prop suggestions for the 225 if I'm looking for a bit more speed?

I hit 44 knots with most of a full tank of fuel (60 gals) another guy + fishing stuff at 5600 RPM. Not sure that I was fully trimmed out either; motor bow up with a touch of trim tab bow down. Flat water with 15-20 mph breeze on the beam.
 
Actually I stand corrected, none of the 300 Mercs have a chrome bore. The 300X doesn't have paint on the block. Just the alodine type finish like the 2.5L 260 and 280 Mercury racing motors which are nicasil (coated bores like chrome). Coated bores are tough as nails and require rebuilding more often. They also spin the he// out of them (7200 to 10,000 rpm). The 3.0L ProMAx like the one advertised did not have 300 hp at the prop. It was something like 280hp. The 300x has the 300 ponies at the prop and is made to turn 6800 RPM with the rev limiter at 7100. My 250 rev limiter is at 5800 rpm and prob has around 230-235hp at the prop but because of the extra displacement over the 2.4L 200 hp Merc(like 175 hp at the prop) I saw a gain of 14 mph when stepping up. The 3.0L 225 and 250 will take some abuse as the bottom end is pretty hearty and they can be hopped up with some electronic mods, tighter heads and the like. But you give up durability IMO. Hot rods cost $$$. Then if it breaks you have to throw more $$$ at it. Fun? Oh yeah. Practical? Well that is in the eye of the beholder. :beer:
 
Shrek, RE:pitfalls of raising the motor up on a jack plate. If the jack plate is electrically adjustable from the console I don't see any issue. Install a water pressure gauge so you know what you have and try it out. Raise the jack plate too high and the water pressure will drop off. Raise it too high and it may ventilate the prop getting on plane or in turns. What motor is your 225? If you are turning it to redline or close you can't gain much by putting a bigger prop on it.
Props are somewhat of a trial and error. Ferm sent me to Ken @ prop Gods who is a wealth of knowledge on props.(Ferm Spare School and others on here too for that matter)
 
As for a low water pick-up, they can actually cost you speed. I know I lost speed on my flats boat with one, but I needed it for teh shallow running I did. The low water pick-up puts more material in the water in front of teh prop which increases drag. High speed boats need them though to force teh water in as teh side pick-ups lose efficiency at a certain point. Somewhere around 60-65 is when you need to consider one is what I was told.
 
Its a 1998 3 liter carburated salt water series. I'm not sure what the red line is, but I would assume that at 5600 RPM, I've got to be pretty close. It is an electro-hydraulic unit so I can adjust it on the fly and I do have a water pressure gauge on the boat, but I wonder about it's efficacy.

As to the prop, it does not appear that I could turn a much larger diameter wheel, but was wondering about upping the pitch a bit. Do the chingered edges of the blades contribute significantly to slip?

I guess all will be answered when I install the jack plate and put the old girl in the lake.
 
THEFERMANATOR said:
As for a low water pick-up, they can actually cost you speed. I know I lost speed on my flats boat with one, but I needed it for teh shallow running I did. The low water pick-up puts more material in the water in front of teh prop which increases drag. High speed boats need them though to force teh water in as teh side pick-ups lose efficiency at a certain point. Somewhere around 60-65 is when you need to consider one is what I was told.
Click to expand...

Good to know, and thanks. We do a lot of marsh fishing here in New Orleans. What kind of loss of speed did you experience with your flats boat? I was really wanting the low water pick up for the marsh. My concerns of starving the motor for water were secondary.
 
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