Joe,jale6666 wrote:My 16.5ft. crestliner came with a 70 hp Evinrude. It has power tilt but no trim. I would definitely like to add trim to this setup to help my performance.
This fall it was running right on 30MPH with two people, full tank of fuel and gear. According to the rpm guage it was hanging right around 5000rpm at full throttle I didn't think this speed was too bad but felt it could be better.
My options are add a trim unit and prop change. Question is, do I just have to add the proper unit to the outboard to do this
Here is a pic of the setup currently
Would I be better to just do a prop change and wait to see what difference this makes? Current prop is an aluminium 13 1/4 x 17
Anyone have a similar engine and can tell me what speed/rpm they are getting?
thanks
Joe
your trim and tilt unit is working properly, you are simply not getting enough trim travel to do what you want. When it's reached it travel limit (approx. 15 degrees) it stops, and the tilt unit is reached. This will not continue to raise the motor for obvious reasons, as Skooter stated. In order to gain trim, you need to offset the engine to the transom. This can be done using a wedge system. A wedge is essentially a block of metal one inch to 2 inches (depending on how much you want to gain) thick at the bottom thinning out to approx 1/8th of an inch at the top. Bolted between the engine and transom, this will offset the egine trim travel As I'm showing in the photo below. After you've done this, you will notice an iincrease in your engine rpm's and bow lift at WOT. I would look for a prop that gets you as close to the 5500 rpm limit of your engine. Thats your optimal power band. You may want to consider going down one pitch and adding a bit more cup to the prop, any local prop repair shop can handle that task, this will give you 150-200 more rpm's and a more efficient hole shot. Hope this helps.
Same pitch ..Same everything! 
Closer examination of the props.. found the new one had narrower blades! Therefore pushing less water causing the over rev... not good! But, on the other hand... I dropped a full MPH on my trolling speed! In my case.. a good trade off. 