Slow to power up...

[Imtrying]

Hi All....Finally was able to get my 70hp Johnson in the water today....Here's my story...I rebuilt the lower unit and slapped it on. It starts fine, idles fine, but when I "hit" the gas, it takes a while to get up to speed. It pushes my 16 footer at 35mph!! Once I'm up there, it runs real smooth, no hesitation, quiet too. I was expecting a quicker plaining time and a hole shot to pull skiers.....I have never run a motor this large, had a 40hp on it that had a pretty good hole shot, but not enough to pull a skier...Could it be the prop? carboration? The motor hasn't been run for three years...I did put new plugs in, and it also has new coils. TIA...Dan

 

[DJ]

Re: Slow to power up...

Without knowing what your top RPM is, we're guessing.

 

[Imtrying]

Re: Slow to power up...

4200 rpm....

 

[mncafik]

Re: Slow to power up...

Im Running a 1987 70 Hp Evinrude on a 14.5ft marlin glasscraft (hand laid fiberglass runabout) got lots of running gear (Anchor, two batteries, twin 6gal fuel tanks, etc etc etc, and I get 6000rpm WOT with a 13"dia 19pitch aluminum prop running 50mph... My only mods were custom 8mil plug wires, wiesco pistons, and boysenn reeds... Your RPM sounds like you are pushing a barge.....<br /><br />Mike

 

[mncafik]

Re: Slow to power up...

What pitch is your prop?<br /><br />Mike

 

[Imtrying]

Re: Slow to power up...

I beleive a 13 1/4 by 17...

 

[Spidybot]

Re: Slow to power up...

Imtrying,<br /><br />If you want accurate advice, you have to state accurate info.<br /><br />If you only have a believed prop pitch, you'll only get 'best believe' answers. If you are actually turning a 17" at 4200 rpm wot, you're proped wrong.<br /><br />Read the lower part of<br /> http://www.props.net/ <br />fore general prop info.

 

[Bass Runner]

Re: Slow to power up...

your rpm is to low get it up to about 5500 and you will see a big difference, find a friend or dealer that will let you try out a smaller dia. prop or one with less pitch and watch the rpm at wot do not over do it much over 5500 or it will trash your motor, might also check the hull at the rear for a hook, if it is hooked this pushes the bow down and then you are plowing farmer john

 

[Imtrying]

Re: Slow to power up...

The prop is indeed 13 1/4 by 17...and I have no way of knowing what the rpm's are...don't have a gauge to show rpm's. I do have aftermarket fins on the lower unit too. So, do you all think it is the prop? Thanks, Dan

 

[Spidybot]

Re: Slow to power up...

It's impossible to say - sounds like the prop is too steep, but a rpm reading is basic in this calculation.<br /><br />If you want to get it right, consider the (rather inexpensive) TinyTach.com<br /><br />Only, and only by knowing the rpm are you able to pick the right prop.

 

[Imtrying]

Re: Slow to power up...

Thanks for all the help, Everyone!...

 

[rickdb1boat]

Re: Slow to power up...

13-1/4 X 17" should be right where you need to be. You may want to drop to a 15" for more hole shot. Depends on the RPM's. Unless the boat is waterlogged or there is a power problem. Either that or you will have to drop down to an 14 X 11" prop to get you in the right RPM area, if you are running 4200 now????. Does it have power trim??

 

[Imtrying]

Re: Slow to power up...

rickdb1boat -- That was just a quess on the rpm's. I have no way of reading the rpm's because I don't have a guage. I have it on a solid 1979 Starcraft that is pretty heavy IMHO. I had a 40hp Evenrude on it, and it pushed it at almost 25 mph. With the 70hp Johnson it does go 35 mph according to my speedometer. So according to my manual, it should be reading a rpm of 4500-5000. No power trim, put I could move the "tilt", or trim with the tilt adjustment rod. I have it now what looks to be at a "90 degree angle". I quess I'll have to move it around and see what happens..........Thanks, Dan