Motor height and prop

[Little35]

I know there have been many threads started about how high to mount my outboard and what prop is best. In the past two days I have used the search function for the forums and read every thread that I could find on motor height and props.

Here is my rig, Crestliner Sport Angler 17' 2" with a Merc 75 F Stroke. I have talked to Merc Tech and they said the first thing to do before repropping is to raise the motor so the cavitation plate is level with the transom. I have read on here that you could raise it up to inch above the keel, but this will only make a differance if you run a motor at or above 100Hp.

I have measured the cavitation plate in relation to the keel and the cav plate is about an inch low. Will raising the motor one or two holes make a noticable diffeance in RPM. I run about 30MPH GPS at 5100 to 5200 RPM 13.25 X 17 Alum, the tag on my motor says that the max RPM is 5500 Merc tech says it is 6000. What would you go by?

I am looking to put a stainless prop on but want to try to take the other variables out of the equation so that I have less trial and error testing of propellers. (I have not found a prop shop in my area that has multiple props for me to test so I want to get as close as I can and do one maybe two exchanges at $40 a piece plus shipping)

Thank you for you time.

[Hot Runr Guy]

If this is a fairly new rig, you've got a lot of boat, weight-wise (1300#) for a 75. Max rating is 125, if it's the walk thru windshield model I think it is. You can certainly raise the motor 1 hole, which should make it flush. But, if you go up 2 or more, I think you'll lose the ability to lift the nose with the motor trim. I'm guessing your hole-shot is not too impressive? Even with raising the motor, I think you'll need to be down in the 15" pitch range prop-wise.
HRG

[Little35]

Yes it is a 2006 and does have the walkthru windshield. I was thinking of trying a Vengeance 13 1/8 x 16 or do you think that I have to drop 2 inches of pitch?
Thanks for the input.

[Hot Runr Guy]

L35,
What kind of load did you have when you got the 5100-5200 w/the 17" alum? If it was a light load, little fuel & gear, I'd drop down to a 15" SS. If the run was with a bunch of fuel, gear and 3 people, then the 16" SS is worth a try. But get the motor up a hole before you start playing with props. Keep in mind, there probably is no such thing as 1 perfect prop for all situations. People always seem to keep an identical prop as a spare, I've always tried to keep a 2nd prop that is different, and exchange them as conditions change (# of people, speed vs. holeshot, skiing, trolling, etc.
HRG

[budsbud66w]

Your mechanic is wrong, you want your cavitation plate so its just getting splashed by water when your at cruzin speed at your full trim.

some boats will be at right high when level with bottom of transom, others wont.


Your gonna want a stainless prop and your gonna wont one that is a bit lower in pitch. that 75hp 4 stroke weights about 20lbs less then a 175hp etec.

id recommend trying a 4 or 5 blade prop. not getting a holeshot is extremely annoying.

[Little35]

L35,
What kind of load did you have when you got the 5100-5200 w/the 17" alum? If it was a light load, little fuel & gear, I'd drop down to a 15" SS. If the run was with a bunch of fuel, gear and 3 people, then the 16" SS is worth a try. But get the motor up a hole before you start playing with props. Keep in mind, there probably is no such thing as 1 perfect prop for all situations. People always seem to keep an identical prop as a spare, I've always tried to keep a 2nd prop that is different, and exchange them as conditions change (# of people, speed vs. holeshot, skiing, trolling, etc.
HRG
As far as the weight of the boat as it is loaded is:
25 gallons of gas = 150lbs
2 Trojan AGM Bats = 80lbs ???
1 Start Bat = 25 lbs
1 80lb Minnkota = 40lbs????
3 tackle boxes = 50lbs
rods and reels = 12lbs
1 20lb anchor
8 Pursuit rod holders = 17lbs
handheld marine radio flares pfds and other mis. items = 40lbs
1 Honda 9.9 kicker = 102lbs
3 people total weight = 520lbs

total = 1056 lbs

I don't tow any skiers or tubes with the boat I just use it to fish. Since this is the first boat that I ever owned I don't know what a good holeshot would be like. My biggest purpose, since I only have a 75hp on my boat, is to get the engine to run near the max RPM limit.
When I take my next readings how accurate is the stock tach or should I hook another tach up to the motor?

The idea of having your spare prop be of different size for different apps is good info.

[Hot Runr Guy]

With that list (and kicker), I'd try the 15".
HRG