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mbroome
06-03-2007, 06:17 AM
Three weeks ago I bout a 79 wellcraft 20 foot ski boat. Supposedly 250 horse, V8, with a fresh rear end. Ive had it out a handfull of times (imcluding mem day!). It's performed beautifully! I DID manage to spin a prop after coming in too close to my fav beach on Barnett resevoir, (live and learn!). Im interested in upgrading my prop and need some help on what to buy! I'm mainly using this to pull the kids on a tube, wakeboard and skis. I have NO clue what I have motor and rear end wise tho. Can someone help me identify this stuff? Its SO nice to take the boat out in the middle of the res with the fam and have my ski out there! I can take a break, get a drink, mess around and then back on my ski again! YAY! I only paid 3k for the boat! Did I get a good deal? Previous owner was a 3rd year med student from my work. He really pampered this thing!
http://a605.ac-images.myspacecdn.com/images01/34/l_3c69a35ce250dceb5bedfe6591a401e4.jpg
http://a968.ac-images.myspacecdn.com/images01/24/l_f06489d03345ecb8e4d1ed2b2c38b8ff.jpg
http://a958.ac-images.myspacecdn.com/images01/47/l_d7fad85b3b47615f86a95375e4d12f25.jpg
http://a306.ac-images.myspacecdn.com/images01/52/l_5cc73817e31d918322cb9977e3c21df9.jpg
http://a691.ac-images.myspacecdn.com/images01/21/l_e6a26aa1b78545010a3a808b5d5cdcfa.jpg
http://a668.ac-images.myspacecdn.com/images01/1/l_f82fe587750d58be77aa80f67ba7d9e3.jpg
Thanks in advance for the help and advice guys!

OCMerrill
06-03-2007, 06:42 AM
Pampered?:confused:
Not near enough info to help you with a prop selection. What was the max RPM at wide open throttle? You want to see about 4400 to 4600 rpm or so on a tach that is verified correct. Older tachs are often not correct.
Choices of prop will be limited as the drive is older. The dia. and pitch should be stamped on the side of the prop. You can get a stock replacement from West Marine (Boats US) although they might have to order one.
I do see its a small block Chevy. I also see it has power steering. On those sea drives you need to be very careful of the large rubber boot mounted to the transom plate. If you can't confirm when it was replaced last...replace it now. A tear in that boot will will sink you fast.
Also do not run with the drive up. These drive use hyd. cylinders under the engine to trim the run angle (if you have that option).
The price you paid seems fair though. Wellcraft is very well respected.

mbroome
06-03-2007, 06:54 AM
RPM is just over 4000 fully pegged.
Im looking at the prop right now and it has 15X17 stamped on it.
prop That i spun (getting it redone, its in the shop) has 38-5'8 15X17 on it. Can someone explain to me what that means?
The boot was replaced less than a year ago when the outdrive was put on. How do I care for the boot? Keep the outdrive DOWN when not in use and armorall it? It DOES have the trim option. Its just really cranky! Half the time all I get is a click! Ive been told I need to go four blade, whats ya'lls take?

mbroome
06-03-2007, 07:55 AM
*bump*

MR.rvrluvr
06-03-2007, 11:09 AM
It looks like a volvo set up...maybe an omc outdrive...but probably volvo...the numbers on the prop are the diameter and pitch....the last number is usually the pitch...in your case a 17 pitch prop...seems small but if you are getting those r's then its probably right...that looks like a heavy boat for a -300 hp motor so I would stay with the 17 pitch....sorry I can't help much but i gave you what I know....just my .02:)

BoatPI
06-03-2007, 11:19 AM
This is an old OMC drive unit with a GM block. ALWAYS run the boat with the drive fully down. Inspect the two gears, one the input shaft meshs with the output shaft protruding from the engine. they look like small rounded gears and should not have much wear present. If this is an electric trim unit then the trim is controlled by two small units attached the the engine mount, or their may be just one unit at the front of the engine motor mount area. It should have wires attached. If it clicks it may be bad or need lubing. Best left to an OMC expert.
Remember when you beach the boat to turn off the engine first them lift the outdrive to prevent damage to the input and output shart gears. this was not the best design ever made, but it will last for years if you are careful with it. I think this is a 2bbl carb and if so it should be about 200-220 HP.

mbroome
06-03-2007, 12:05 PM
tyvm for the help guys! I'll take any advice I can get!

HocusPocus
06-03-2007, 12:11 PM
i had an old 23' daycruiser with this OMC setup and it ran like a champ, if i remember right i ran a 19 pitch prop and put one of those "whale tales" on the outdrive to get it to plane quicker. keep a close eye on the transom boot as they do leak so make sure your bilge pump is working.

OCMerrill
06-03-2007, 12:13 PM
15" Dia w/ 17" pitch. This means that one revolution of the prop will move 17" of distance.
Not a 100% true because there is loss in slippage, etc. Anywhere from 10 to 20% lost.
Verify the tach the get either the same pitch with a 14" dia. or go to a 15" pitch with the same dia. to bring the rpm up. You will get a better hole shot this way as well.
It's a Johnson/OMC Sea Drive and not a Volvo. There are no u-joints just knuckles that lock together when the drive is down. This is why you cannot run with it up or trimmed up using the tilt button.