Is 1987 Gt 150 running right

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Hello again, After switching from force to Johnson I must be a little paranoid. I'm running a 17 foot Fabuglas open bow and the Johnson I put on had a 22 pitch stainless prop, I could only gain about 4800 rpm at wot with it, so I went down to a 19 pitch alum. prop and with little gas got 5200 rpm out of it, put 25 gallons of gas in today and 5000 rpm up river and the 5200 again going back down speed is between 45 and 50 not on GPS. I been in the prop section and walley seems to think there's a problem so I'm over hear now seeing what you all think. I mentioned to walley that when I put in, it vibrates a little in the no wake zone but holds a even 700 rpm. You click it one more time and start going it smooths right out. I hope I'm just being paranoid here, The motor does not miss a beat on the river and the boat probably weighs at least 3000 pounds maybe less with normal load and full gas. What do you all think??????????. Thanks in advance, Chris
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Is 1987 Gt 150 running right

What is the gear ratio? If you can't get close to 5800 RPM max, I think you are still too high on the pitch. Have you tried trimming the motor out when you are on plane? You want the A/V plate flat parallel to the water.

I could not tell from your picture, but is the A/V plate a little above the bottom of the boat?
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Is 1987 Gt 150 running right

yes it is by about 2 inches maybe a little less. I trim as far as I can go then back just a touch. I don't know the gear ratio. Is there a way to find out???? About the pitch I'm thinking that a 17 stainless would do the job.
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Is 1987 Gt 150 running right

You can get the gear ratio from the owners manual or the service manual if you have them. They are listed in the front in the specifications chart. If not, someone may be kind enough to look it up and let us know.

You need the gear ratio to calculate the theoretical maximum speed that the boat could go at a given pitch; That way you can calculate the slip.

The pitch is the number of inches that the boat would move in a perfect state with each revolution of the propeller.

That 17 would make sense to me, but I would run it by the prop forum. Those guys are the experts on the propellers.
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Is 1987 Gt 150 running right

I see. I'll try to get a manual, I get one with every thing I buy just hav'nt gotten to this one yet in the mean time if anyone out there can help us out the model number is J150GTLCUR.
 
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