1988 Shadow Bass Boat

[jelbass]

Here what I've got a 1988 Shadow Bass Boat, 5 persons or 650lbs(my son and I weight out at about 395lbs, just put a 1990 150GT Johnson on the boat and it weigh out at about 381lbs and the max weight on the boat is 1075 persons, motor and gear. with 3 Batteries and gear (trolling motor, rods, tackle) and all we may be pushing about 1200lbs. By the way the boat weigh in at about 1000lbs. We've been running a Johnson rebuilt 140 HP for about 10 yrs. and she top out at about 42 or 45mph. The GT150 didn't have a prop to come with it. Anyone got any good suggestion on a prop to start out with on the 150GT? Can anyone tell me the max RPM on the GT150? Thanks for any help and may God Bless All.
Jelbass

 

[Dhadley]

Re: 1988 Shadow Bass Boat

Try to target 5800 with an average load. If the set up and prop were correct for the 140 you can start with the same pitch for the 150. The different gear ratio will make up the difference. However -- don't ya love that? - if the 140 didn't have the torque to get it up and loose it's a whole different ball game.

Let's start with how it ran with the 140. What prop, what rpm, what speed. Jackplate? Did it require a lot of positive trim to get the nose up?

 

[jelbass]

Re: 1988 Shadow Bass Boat

Thanks Dhadley, The Shadow can only be rum with the jackplate and with the 140 Hp I used a 13.5 X 15 allumminun at first. It was slow come out of the hole, and it would wet you during a run (it was like the front was up and front dash back was down) and top speed was 42 to 45 MPH using the trim up at 5500 to 5800 RPM. Keep in mind this boat is rated for 180 HP and from what I can learn this boat was made for speed or to be fast. I pick-up a S.S. prop that was use with the same numbers and it ran about the same as the other prop. This time I'd like to get a prop that will get me up a little fast and keep me from getting wet. Thank you for your help and may God Bless.
Jelbass

 

[Dhadley]

Re: 1988 Shadow Bass Boat

A 15 seems a little small for a 18 1/2' (if I remenber correctly from your other post) but maybe the V4 didn't have enough torque to get the boat up. I'd think that something like an 18 or 20 Raker or a Turbo Vector would work. Obviously we need something with bow lift.

Do you have any V6 props to test with?

 

[Ron G]

Re: 1988 Shadow Bass Boat

If thats the shadows im thinking about they'll fly,they have a step pad under them.They also have alot of lift built in to the hull.a buddy had one with a 200 merc on it that one run high 70 low 80 all day long.

 

[jelbass]

Re: 1988 Shadow Bass Boat

Ron G that the Shadow!!!!
Not yet Dhadley But I looking and asking about one. Will any OMC v6 prop work on the 1990 150? Another question, I've been looking on Ebay at used props and many are posted as 15 spline, does this main that they would work on my GT150? Thanks to all and God bless.
Jelbass

 

[Dhadley]

Re: 1988 Shadow Bass Boat

Yes, you need a 15 spline prop with an OMC (Evinrude / Johnson) hub.

 

[jelbass]

Re: 1988 Shadow Bass Boat

Got a 14.25 X 24 from a buddy to try out on my boat Sat. We were fishing a club tourney down on Santee Copper. I couldn't believe the different in this boat with the GT150. It was like a new boat to me, it come out of the hole like a bat out of hell (FAST) and on top of the water in no time at all. We went to the river and she ran 55 MPH @ 5200 to 5400 RPM's that was about all the RPM's I could get. I had problem getting the Trim gauage to work, so I was running with out a gauage. By not having the motor trim high enought cause the RPM's not to max? Next question the trim guage that was use on the 140 has 4 poles #1.one at top has a L (light), the one below that #2 one(right) has a I (not sure),next one between has a #3 G(ground) and #4 to the left of #2 has a S(not sure). Can someone tell me what I and S stands for? On the GT150 the harness for the trim has 5 wires three of them plug into the trim switch and the other ones, one is black(has a circle connector) and one is white with a plug on it. Are these suppose to go to the trim gauage? Thanks and may God bless all.
Jelbass

 

[muchco]

Re: 1988 Shadow Bass Boat

"I" stands for ignition. "S" stands for sender. The white wire should go to the "S" terminal and the "I" terminal should be hooked to an ignition source. The third unsued terminal on the back of the guage should be the ground.
From a prop stand point I would suggest a few pitches lower. I'm running a 1987 Evinrude 150XP on 17' 5" Larson runabout (2200lbs loaded) 4" manual jack plate prop shaft 4" below the lowest part of the boat. I'm running a 14 1/2" X 22 pitch Raker at 5750 rpm going 57 - 58 mph gps. I have had my 22 Raker B&B and taken out a little pitch and added some tip cup to accomplish this. I hope this helps.
Dhadley is one of the best set up guys on these forms and he will tell you that you will want to get the rpm up. 5800 is the number your looking for anything under 5500 is not going to be good in the long run for your GT150.
The trim guage not working will not affect how much you can trim up, it's just and indicator as to were your at. If you did not have the engine trimmed right up it would affect your rpm. From what I see I would think that you did have it trimmed all the way up though. Was the speed a GPS speed or Speedo speed. The numbers you have given show a slip of 20% at 5400 and 16.6% slip at 5200 which is way to high. you should be more in the range of or about 10%.
I'm sure Dhadley will chime in. He's been very helpfull to myself on several occasions.

 

[jelbass]

Re: 1988 Shadow Bass Boat

Speed was by Speedo speed! Next questions, will an allumminun prop work as well as the S.S. prop? On the prop I used this weekend it had two holes drill in it, Why and what different does theses holes make? Thanks and may God bless all!

 

[jelbass]

Re: 1988 Shadow Bass Boat

O.K. another dum question. I've been looking at props on Ebay and some them has left hand and right hand. What different does it make if LH or RH? Thanks and may God bless all.
Jelbass

 

[muchco]

Re: 1988 Shadow Bass Boat

Most speedo's are quite inaccurate, I would suspect that you were going less than 55 mph. To get the best setup, you should be using a speed from a GPS or radar gun.
Stainless Steel props will most definetley out preform Alluminum props. If the holed your speaking of were near the base of the hub and behind the leading edge of the blade or blades, these are vent holes. They aid in improving the hole shot by letting exhaust gas pass over the blades, and airate the water. This allows the prop to slip and increase or improve the hole shot. Once you get up to speed the water rushing by seals up the holes as if they were not even there.