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i have a 1988 model 18' wellcraft fisherman with a 96 mercury 125. boat and engine r n great shape. when i take off the boat seems to get on plane pretty quickly but once it does thats it. no faster. top speed is 25. The anti cavitation plate is app 4.5 to 5 inches above the bottom or keel of the boat. ive been told that it needs to be even with the bottom of the boat. i added a hydrafoil to the a/c plate but that doesnt seem to do anything. when the boat is on plane or at its top speed 25 mph ( 5600 rpms) the bottom of the a/c plate is touching the top of the water. it is not submerged. i hope this is enough info for you guys to be able to help me out. i think the engine needs to be lowered. also when i m running and i try to make a sharp turn it almost wants to stop and the engine revs up. i think its called a blowout or slipping. thanks
Great Boat!! The cavitation plate needs to be level with the bottom of the hull. You must have a 20" shaft motor on a 25" transom. Who screwed that up? Take a picture of your boat and motor . . . with the cavitation plate. Bay Engineering makes 5" extensions for most motors . . . the price is about $600 for 5" housing, shift shaft, Drive Shaft, Water tube extensions and longer bolts.
yup its too high.....i have your boats brother....a 1990 18 sport........do you have a 20 inch motor on a 25 inch transom? if so you gonna need a jackplate.......
dragn....where ya located at? i currently have a 25 inch motor on a 20 inch transom on a jackplate...1994 140 johnson...my problem is it wont go high enough lol
dragn....where ya located at? i currently have a 25 inch motor on a 20 inch transom on a jackplate...1994 140 johnson...my problem is it wont go high enough lol
Shame your Johnson won't go high enough, you know they got drugs for that now?
I've got a 2001 Wellcraft Sportsman with a Fii5 Yammie, it just breaks 30 MPH at WOT loaded.
hey thanks. ill try and get those pics shortly. i definately think i need a jack plate. i can get a manual jack plate for about $170 here in biloxi. it will allow me to drop the engine up to 5 inches.
The anti cavitation plate is app 4.5 to 5 inches above the bottom or keel of the boat. ive been told that it needs to be even with the bottom of the boat.
A jack plate is effective for running a 25" motor on a 20" transom, but NOT the reverse.
You can't drop the motor 5" with a manual jack plate unless you want to put your motor underwater, bend your control cables at a 90degree angle, and GOOD LUCK tilting the motor up (forget about having trim and tilt). Take a picture. Can you lower the motor a few bolt holes or are the mounting brackets touching the top of the transom.
You measure the boat transom from where the motor would rest on the tiop, to the bottom of the hull. The motor you would measure from the bracket the motor rests against the transom, to the anti cavitation plate. That's the large horizontal plate above the prop. A shortshaft is 15"s, and longshaft is 20"s, and extralong is 25"s, and they now have a 30" shaft size.
Mine says 125 ELPTO. so does that mean i have a 20 in shaft and need a 25?
ill leave that one alone but what i will say DooFighter is that sounds like my life story!
Yep, what he said is correct. Being the motor is a 96, there make be a few of them around with 25" shafts and a blown powerhead you could buy for parts. I think that would be the best way out of your situation. How did you happen to land up with a longshaft motor or an xl transom?
I just bought the boat a couple of weeks ago and the gentleman i bought it from failed to tell me about it- i guess. When he bought the boat it had a 115 merc on it and something happened to it and he put the 125 on it. He probably made the mistake of putting the short shaft engine on it. The rollers on the ez load trailer were messed up so i couldnt launch the boat to take in on a (water) test run and there were a few other people lookn at the boat. I got a little anxious and a good deal on it so i bought it. So i guess that part of it is my fault.
These are very well respected kits for converting 20" motors into 25" motors. They come with everything you need. You could find used parts - 25" lowerunit, XL shift shaft, XL water tube, spacer, bolts, etc. . . . or just get the kit.
dragn..Bshrimpin is right...you cant drop a motor down 5 inches or it will damn near be underwater.......i'm moving to panama city ,fl at the end of may...and i'll be running back to louisiana quite often through biloxi....i'd be happy to trade motors with ya lol...i got your 25..you got my 20!
I sure do appreciate the help and info guys. I think im gonna have to go with the extension kit though. After checkn out the engine and compression test and trusting the info the man gave me i bought the boat from i believe i have a good solid (low hours) engine and it would be worth the extra money for the kit.
BigShrimpin you never told me if you are or were a shrimper or not?
wellcraft 18 fisherman question 
also when i m running and i try to make a sharp turn it almost wants to stop and the engine revs up. i think its called a blowout or slipping. 
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