need advice on motor height !!!!
 

i have an 18ft team persuasion custom aluminum boat that i had a gill bracket built for because i bought a 20 inch shaft 175 evenrude etec motor, someone said if i trimmed all the way down and was throwing a rooster tail on each side of the cavitation plate that my motor needed to come up some more to gain more top end , my boat weighs about 1600lbs and does 49 mph at 5700 rpms they say i should be running in the mid 50s to low 60s,i will have to buy a jack plate to bring it up higher,and have the prop worked to bring the rpms back down and keep the top end , IS THIS TRUE??? ANY HELP WOULD BE APPRECIATED , THANKS

will tak pics tomorrow, thanks , right know the cavitation plateis about an inch above the bottom of the boat,but some one told me the etec have to ride high,,and i do throw a rooster tail on each side trimmed all the way down

I worked at the prop shop for 3 years. If you want one afternoon I can meet you at the verm river launch in abbeville and we can see what needs to be done. Your motor height sounds right,you probably don't have the correct prop.

we cant launch at the river they are re-doing the whole thing but i am turning just about the max rpms for the motor which is 5850, but thanks i live between abbeville and intercoastal city ,i launch at maxies,the dealer said that is all i would get out of the motor but the guy who built the gill bracket said i shoild not have any rooster tail coming off the cavitation plate when trimmed all the the way down ,he is the second person that said i am dragging to much motor ,i have a 14 3/4 x17 prop, thanks all info is helpful,and i would sure take you up on your offer if the river launch were open

What brand of prop are you running? I always judge the height while trimmed up running,not down. You need to be able to see the cav plate and not have alot of backwash. What is your main concern,speed? High 40's sounds pretty close with a 1600lb boat with a 175. We mounted a 250 verado on that same hull for WLF and it only did 60. Looks like maxie's launch in your avatar pic...

yes that is maxies launch, and this was a wlf boat at one time, i can see my cavitation plate when trimmed out, so maybe that is all i will get out of it,but i do have a lot of back wash,and i am running a viper prop ,and i dont cavitate on take off.

As high as you can get it and maintain water pressure.

Here 'ya go for a basic set-up; you will need a 24" level and tape measure (and a helper makes it a whole lot faster).
1.) Hold the level firm to the bottom of the boat at the transom; with the tailer jack raise or lower to level; measure distance from top of level to floor, slab etc.. jot down measurement.
2.) Remove prop and place level on cavitation plate of engine, tilt back or forward to level; measure center line of prop shaft to floor, slab etc. jot down measurement.
3.) Subtract prop shaft distance from bottom of hull measurement. As a starting point you want the c/L of prop shaft 2 1/2 below the bottom. This should put you within 1/4 in up or down of the optimum height for your set-up... Hope this helps.

Is your main concern top end speed?

thanks guys and yes my main concern is top speed ,that way i can pull back on the throttle and save fuel, and maybe still get 40 mph at cruising speed

my boat has a pad on the bottom of it. i just leveled the boat and the motor, the bottom of the cavitation plate is 2 3/4" above the bottom of the boat

You need a bigger diameter prop for that heavy hull. You may not gain much or any speed,but you will have a better cruise speed. It is hard for me to explain it online but more top end speed does not mean better fuel economy at cruise speed. The larger diameter prop will carry the weight and lift the boat more. You will notice you have to use less throttle and trim to make the boat respond. Get you a mercury mirage plus. Hands down the best prop on the market for heavy bay style boats. The mirage has a universal hub,they make kits to fit any brand including the etec. A new one will set you back around 600 bucks,but it will pay for itself in the end. Call Phillip at the prop shop,tell him Ryan sent you. Buy a prop with him and if your not satisfied with the prop out the box they will tune one it for no extra charge within 30 days of purchase.

this is it. hope the pics attatch

Motor height looks perfect. Get that viper prop off there,it was made for bass boats. The whale tail is usless too,you can actually hurt performance and cause drag. Whale tail is a bandaid for a prop issue.

i was thinking about changing the prop, but i am turning close to the max rpms with this prop

thanks montauk

It's not so much your rpm's it's the blade design and diameter that is hurting your performance. Anytime bro,don't mind helping out. Prop setup can be a pain in the azz,very minor adjustments can make a huge difference.

Larger diameter prop will make your boat feel like a sportscar!!

I had same problem as you. Big heavy boat, little tiny prop.......Went to a 15 1/4 diam prop and Igained performance in holeshot, handling, and top end!!!

thanks guys ,i put the whale tail on it to help lift the back when running,but i guess with the right prop i will give me some lift

thanks guys , i put the whale tail on it for lift, but i guess when i find the right prop it will give me lift.. does anyone have a prop to fit this motor that would help? for a decent price, thanks again