HP Upgrade

[jayselle]

I have found a new home for boating advice. The amount of knowledge shared by everyone is unbelievable.<br /><br />I just bought a new 2002 CraigCat E2. It is 11' long. It came standard with a Mercury 25HP, the model number is a 2003 25E. The max horsepower rating is 25HP. It could certaily use more power though, its just feels way underpowered. The boat should do about 30-35MPH, however, I would venture to say its about 25MPH.<br /><br />The weight difference between the 25HP and 40HP doesnt seem to be that great. Would it be feasible to upgrade to a 40HP motor and if so how does one go about uprading? Do I just sell the current one outright then buy a new 40HP. The current 25HP motor is brand new with just a few hours. Thanks for any help in advance.<br /><br />IF a horsepower upgrade is not feasible is there anything reasonable I can do to increase performance? I am mechanically inclined so I can do the work myself. Currently there is an aluminum 13P prop, would stainless steal be a noticable difference?

 

[Barnacle_Bill]

Re: HP Upgrade

What is your RPM at WOT?

 

[FlyBoyMark]

Re: HP Upgrade

The short shaft Mercury 40 HP weighs about 204 lbs and the Merc 25 HP weighs about 110 lbs. The Merc 25 should do about 30 mph with a 600 lb gross load. What is the weight of the boat, gear and yourself plus fuel. The Merc 40 HP will push your boat to about 38-40 MPH for your application. Are you sure the hull design will work at that speed? Another consideration is the strength of the transom for the DOUBLING of TORSIONAL loads not the weight. And one last consideration is your state laws on overpowering and insurance regs also. In Florida, where I live all this is okay, but could be quite different where you live. In addition, this is NOT a modification for a inexperinced boater...

 

[jayselle]

Re: HP Upgrade

Thanks for the replys. I am not sure of my RPM's at WOT because there is not a tach. I have plans on installing one as a handheld soon as I figure out if this is a viable option to do.<br /><br />I am not an inexperienced boater, I also own a 1979 Charger bass boat with a 115HP Johnson. I bought this boat just for fun.<br /><br />Here is a link to the boat:<br /><br /> http://www.craigcat.com <br /><br />My particular model has the option for a Yamaha or Honda 25HP and I believe those weigh around 150 lbs. I can re-enforce the transom if it becomes necessary.<br /><br />The boat was 250lbs, motor 110, two people about 300lbs, gear about 20lbs. Total of about 680lbs.

 

[sundog]

Re: HP Upgrade

I agree with flyboy. just took a look at the craigcat design, and I wouldnt consider it...to little boat, way to much motor (40hp). a 25hp should give you the 30-35 you looking for easy, with that design. IBN is on target...check your RPM at WOT.

 

[jayselle]

Re: HP Upgrade

Originally posted by sundog:<br /> I agree with flyboy. just took a look at the craigcat design, and I wouldnt consider it...to little boat, way to much motor (40hp). a 25hp should give you the 30-35 you looking for easy, with that design. IBN is on target...check your RPM at WOT.

Do you know of a way to check the RPM on a 25HP motor? I mostly likely will have to invest in a manual to figure out the wiring scheme if there is the option.<br /><br />I have a feeling the RPM's are low, in the 4,000's just from the way it sounds. In which case I would need to decrease the pitch. I am worried the added weight of a SS prop over aluminum will actually hurt more than it will help.

 

[sundog]

Re: HP Upgrade

decreasing the pitch of the prop isnt going to help your speed. without checking RPM, Id rent/buy/borrow a GPS and check your speed to see if your actually slow (you mentioned you didnt know how fast your actually going). if slow, you need to check RPMs somehow. also, do you have a well vented tank? if RPMs are down, may be a fuel problem...

 

[jayselle]

Re: HP Upgrade

Originally posted by sundog:<br /> decreasing the pitch of the prop isnt going to help your speed. without checking RPM, Id rent/buy/borrow a GPS and check your speed to see if your actually slow (you mentioned you didnt know how fast your actually going). if slow, you need to check RPMs somehow. also, do you have a well vented tank? if RPMs are down, may be a fuel problem...

I have a 6.6 gallon Quicksilver tank and it uses a vented gas cap that has no trouble. The engine runs strong and smooth. I think I just want to much from this little boat, speed that is.<br /><br />When I am the only one driving the weight is centered to the right and it pulls very hard to the right. The anode (tab on cavitation plate) is all the way to the right. It also porpoises like crazy when just by myself. I have been told the boat was desinged for two people and if the weight is distributed differently, like just one person, it will porpoise and pull hard in that direction.

 

[FlyBoyMark]

Re: HP Upgrade

Look up "Tiny Tach" on the web and order one, Tiny Tach size of a match box and cost about 30-45 bucks. They havem' jus for outboards.....<br /> I would check your throttle linkage throw, That little booger with one person should be doing about 5 MPH more...

 

[FlyBoyMark]

Re: HP Upgrade

ALSO...I got news for you...that boat with a 40 HP on it would do OVER 40 MPH AND TORPEDO rite through a wave!!!!!!!!! Wanna know what a wall of water feels like at 40 + MPH?????? Jus' ask any barefooter what feels like to take a tumble!!!!!!!!

 

[funpilot]

Re: HP Upgrade

The web site says that the speed is "up to 30 mph". Looking at the design, the twin pontoons, and the width for the hull length (and the fact that it appears that even when planing, the boat has a lot of wetted surface) I don't think it will go much faster. More horsepower isn't going to help.<br /><br />Have you considered a different water toy, like a PWC or a jet boat? You can pick up one used for a lot less.

 

[sundog]

Re: HP Upgrade

LOL! flyboys visuals are pretty good. I can see why it would pull and porpoise...from the specs it looks like the hulls are designed to flex, giving you a smoother ride in rougher water (although being out in rough water in that boat kinda defeats the purpose). with you on one side, the pull is from your hull being down. the other hull is 'loose'...at speed its probably rocking back slightly, pushing your hull forward slightly, and porpoising. that boat isnt stiff enough to handle more HP...it might get dangerous.

 

[jayselle]

Re: HP Upgrade

Originally posted by funpilot:<br /> The web site says that the speed is "up to 30 mph". Looking at the design, the twin pontoons, and the width for the hull length (and the fact that it appears that even when planing, the boat has a lot of wetted surface) I don't think it will go much faster. More horsepower isn't going to help.<br /><br />Have you considered a different water toy, like a PWC or a jet boat? You can pick up one used for a lot less.

The creator of the boats claims 35MPH, but that might be in perfect conditions. The boat is a lot of fun and burns about 1 gallon of gas per hour. It handles waves surpisingly well. So far it has handled 5-6 foot waves without a problem and never takes on water. Every once in awhile it can catch some air, so I imagine at 40mph that would be even wilder. <br /><br />I will get a tach on their ASAP and see if a different prop will help her out. Does anyone have experience switching from aluminum to stainless on low horsepower motors?<br /><br />I had a jetski. The price of 93 octane and the way those things guzzle gas I had to stay in one place because you can't get too far. Not to metion jetski's are just downright annoying, at least here in Oklahoma. Jet boat...hmmm...that sounds like fun, but I always assumed they were very expensive.<br /><br />Thanks for all the help guys.

 

[funpilot]

Re: HP Upgrade

I hear you jayselle,<br /><br />The jetski drive (and by extension) the jet boat drive are no where near as efficient as a well set up outboard with the right prop. I read somewhere that a jet drive gives up about 33% output to a similar sized outboard, so my 120 hp sport jet is like having an 80 hp outboard.<br /><br />That said, a lot of people do become disenchanted with the fuel consumption of their jet drive because they run them WOT all the time. When I throttle back from 5000 to 4000 rpm, my speed drops, but still, 34 mph at 4000 sounds good to me. I'm burning a lot more than 1 gph, though, but it is 87 octane in a 21 gal tank!<br /><br />Looking at the video of the diver hopping on the pontoon, the boat seems more stable then I thought it would be, but the fact that you can list the craft under power with one on board tells me it doesn't really get on plane. The jet boat I own will list at normal hull speeds, but once I get on the ride plate and plane out, it is level as the plains outside of Wichita.<br /><br />I got my jet boat for free, all I had to do was rebuild the engine.<br /><br />take care, and good luck.