Speed question

[carbineone]

We took the little GW Invader out today,the one in our avitar and ran the GPS.I am kinda dissapointed in the speed and guessed it way faster than that lying GPS did.But in actualatity the speed was 31MPH on the GPS.Just seems much faster,The setup is a 1974 Evinrude Lark 50HP.The cavitaion plate is set even with the bottom of the keel and the prop pitch is 13x19 Was hoping for some better speed but it does plane out in less than two seconds.Does this performance seem on par to you at all?I am happy with it and it sure seems to go but expected a little more speed.My next question is it runs perfect and to me the RPMs seem nice in the range thats its running but maybe a little low definitley not overevving..I used the old 1963 dual controls and cables and am wanting to know how to tell if we are getting full throttle also?I know its a lot of questions but let me know what you think...Thanks

 

[Chris1956]

Re: Speed question

I am not sure what kind of boat you are running. If the RPMs are in the max WOT range, then it is propped correctly. If you have power trim, make sure it is trimmed out to the max speed. if no PT, you might change the trim pin one hole out in the transom bracket, and test for increased speed. Normally the second hole is the starting point, and if you could run the motor effectly in the 4th hole, that might give you some more speed. Too much trim will preclude you from getting on plane.

 

[carbineone]

Re: Speed question

Heres a pic of the boat,its the ten foot Mini GW in the little pic.The second hole up is where we ran it today.Will try as you suggest and move it to the third hole.Do not get me wrong we are happy with the speed but just expected a little more from a ten foot boat running a 50HP. I just do not know how to tell however if its getting full throttle adjustment through the cables as like I say its a older throttle-shift dual setup from a older motor.I hate the single stick ones..The older ones are more dependable and less complicated in my opinion and take up less space and thats important in our small cockpit.Oh it has no power assists at all..The gear ratio in my owners manual says 12:32 if that means anything to anyone...Thanks

 

[kenmyfam]

Re: Speed question

Check the cav plate height while on plane if possible. See how much is submerged.

 

[Fed]

Re: Speed question

You're chasing your tail without a tacho.

 

[MushCreek]

Re: Speed question

I agree with the tach. That lower unit is geared REALLY low! You sure it's not 12:23? If it's actually geared that low, you're going to need more prop pitch to really get going. How was it riding in the water? Was the bow kinda low? Try some different tilt positions, but be aware that that little GW will get squirrely if you get the bow up too much. If all else fails, cut your losses, send me the boat, and I'll see that it's properly and humanely disposed of.....

 

[wilde1j]

Re: Speed question

You DO need a tach and, while kickout is important, so is motor height. When the motor is at the correct height, the cav plate will be fully uncovered @ WOT. If the motor is too deep, you get excessive drag and resultant lower top speed and lower RPM as well. That motor should turn 5500 RPM @ WOT.

 

[carbineone]

Re: Speed question

Yes fellas thanks.I just posted a new thread trying to find out what tach I can buy for this 1974 motor that will work on my Magneto system and order a tach tommorow if I can find what kind I need.Boat does not ride high in the front at all and handles very well actually.We go 31 around turns and its great.
I will watch the cav plate next time out.Unless the owners manual is a misprint it says 12:32.Yes I am about ready to send it for disposal and would but shipping it to you would just be too much I am afraid,LOL Thanks and if I find out what kind of tach to get we will update this when we have a Tach reading...Forgot to mention the cavitation plate runs right even with the bottom of the boat and I cannot get it above it so its stuck there,no higher.

 

[wilde1j]

Re: Speed question

Your picture of the stern isn't very clear, but it looks like the motor bracket is sitting right on top of the transom, which suggests there are some upward mounting holes available. You move it up by loosening the bolts in the slotted holes, remove the two in the round holes, jack the motor up and reinstall the removed bolts and tighten the ones in the slotted holes. I use the trailer tongue jack, along with blocking under the skeg, to move the motor. Just do it on level pavement and block the trailer wheels, so the trailer can't move. Very simple and quick unless someone slopped 5200 sealer around the holes.

 

[F_R]

Re: Speed question

wilde, his motor does not have the bolt-on stern brackets, it has clampscrew brackets. Changing the motor height isn't that easy.

carbineone, your motor does not have a magneto. The tach gets its signal from the alternator, counting the AC pulses, so you need an alternator tach.

As for the throttle, put the motor in gear and watch the action of the throttle on the motor as somebody advances the control (motor not running). You should see the spark advance move till it goes up against the rubber bumper on the full advance limiter screw. Then any more movement of the control opens the carburetor butterflies till the plates are in a horizontal position. That is wide-open throttle and all she's got. I might add, don't mess with the full advance screw.

Sometimes the spark advance gets sticky and doesn't go up against the stop. That usually causes it to stumble and even quit running, but if it is just a little bit shy, would cause lack of power.

 

[carbineone]

Re: Speed question

OK,I am just going off my owners manual saying it has a Magneto Breakerless
Capacitor Discharge.So any of the tachs that say 12 pole 6p will work regardless of if they are for a newer motor than a 1974?You are right on the height adjustment it will not go any further so I am stuck with the cavitation plate running even with the keel.The engine runs great.I did what you told me and when I start advancing the throttle the part reaches the rubber stop and the butterflies are still not open very far but after it hits the stop they do open fully horizontally when the throttle lever is full ahead.Hope you understand what I am saying.In other words the advance hits the rubber stop way before the butterflies are completely open.Is that the way it is supposed to work or should the arm hit the stop at the same time the butterflies are completely open?....I am more likely going to buy one of those little tiny tachs if they will work.I assume the timing advance works like it should as smooth as the motor runs at all RPMs..Thanks

 

[Banoe]

Re: Speed question

I had a 14' MFG with a 73 50hp Evinrude that would do 34-35mph on the GPS but I had a lower pitch prop on it say a 17" pitch. When I put a 19" on it it just wouldn't rev up and get going. Some times less is more.

 

[wilde1j]

Re: Speed question

I have raised smaller motors using 1/8" wood shim sticks for racing. I suppose you could raise the motor some using the same strategy. Anything major would require building up the transom top, which most people wouldn't care to do.

 

[carbineone]

Re: Speed question

OK everybody heres the story so far.I went and bought a supposedly 100.00 fancy Teleflex Tach in the pics used very little for 30.00 and set it to 6p.I hooked the gray wire to the send terminal,the ground terminal grounded and the power to the accessory on the switch,I turned on the key and the tach dropped and zeroed as I think they should.I started the motor in the tank and nothing,stayed at zero.Checked my connections and all were good,I was getting mad that maybe he sold me a junk tach but he said it worked.I went back and pulled the motor hood and the little round thing in the center photo,I think it may be the rectifier,I tapped it and the tach worked fine.Tapped it again and off again,If I do not tap it again it seems to stay working but maybe not when in motion.Any idea why the rectifier thing may be doing this?I have a couple bigger Johnsons from the same era, a 85HP and a 115HP.Any chance either of those rectifier may work? Going to check the RPMs soon out on the water to let you know what its doing....Thanks

 

[wilde1j]

Re: Speed question

I think the rectifier is grounded through the metal case, which would explain perhaps why tapping it made a difference. In any case, I would make sure the case is well grounded. The other possibility is the rectifier has an intermittent open circuit. Connect a DVM to the battery and see if the is charging going on or not.

Check the AC voltage to the yellows going to the rectifier ... if > 20VAC, the stator is OK and the rectifier or wiring has a problem.

 

[carbineone]

Re: Speed question

Jim,OK I will have to dig up my voltmeter..Are you saying the rectifier should be grounding to the case or the rectifier should be isolated from ground?Thanks

 

[wilde1j]

Re: Speed question

Case should be grounded.

 

[carbineone]

Re: Speed question

OK,theres a chance that there may be paint under the rectifier then as I believe someone repainted the whole motor at one time.I will take it loose and scratch the paint behind it to be sure and re-tighten it up....Thanks

 

[carbineone]

Re: Speed question

Hey everybody I just started a new thread on this over in the Prop section stating the outcome of the test today with the Tach.In short but explained more over there we ran the same 30MPH on GPS of course but only showed we are running at 4200RPMs Thanks

 

[wilde1j]

Re: Speed question

Should ~ 5500 RPM @ WOT. Way too low.