1980 50 hp Mercury wants to go faster

[troy_ernst]

I need to know what will make my boat run faster. I have a 1980 18 foot Starcraft SS with a 50 hp Merc. The highest speed I can get on GPS is 25 mph and I think it should run faster. I do not have a tach so I can't tell how many RPM's I'm turning, but the little motor sounds like its running good never really gets to were it sounds like it is over reving or anything. At 25 mph I had myself 175 lbs, my wife 158 lbs, and three kids 80 50 & 35 lbs in the boat. I have a 13 pitch prop that cam with it and a clean bottom on the boat. I have changed the plugs am perfect on my oil mixture (pint to 6 gal) and have cleaned the carbs and had a mechanic adjust them on the muffs. I have tried several trim positions as I don't have power trim. Can anyone help with this issue?

 

[capt-pete]

Re: 1980 50 hp Mercury wants to go faster

I think that sounds about right, actually. My 80 HP mariner and runabout hits 35 and if I really work on trimming it out I can hit 37, with a 19 pitch prop.

 

[Moody Blue]

Re: 1980 50 hp Mercury wants to go faster

Want to run faster, get a bigger motor if the boat is rated for it.

You are asking alot of just a 50hp motor pushing an 18ft boat with a 500Lb payload. If you don't know the rpms and the motor sounds like its not over revving, then its pretty hard for anyone else to take a guess at making improvements.

Your best bet is to properly balance the load in the boat and trim the motor for optimum ride. The 13" pitch prop sounds a little small BUT again without a tach you don't know.

 

[troy_ernst]

Re: 1980 50 hp Mercury wants to go faster

How do I put a tach on it?

 

[rainbro]

Re: 1980 50 hp Mercury wants to go faster

You wont go any faster with that engine and that much weight.It sounds pretty fast actually.I have an 83 50 hp on a 14 ft aluminum.With 400 lbs of occupant and fishing gear, I get about the same speed.

 

[troy_ernst]

Re: 1980 50 hp Mercury wants to go faster

I really thought this thing should run in the 30's. I am very disapionted I guess I will sell it and get something else.

 

[fasassvalk]

Re: 1980 50 hp Mercury wants to go faster

I think you are expecting to much out of the 50 hp.
my 18 ft aluminum with a 125 hp runs out 39-40 17 pitch prop, loaded ! So I think the 50 is being all it can be.

 

[moorecomp]

Re: 1980 50 hp Mercury wants to go faster

I recently rebuilt my brother-in-laws 17' Sea Nymph 170SS and his 1966 Mercury 650 (4 cylinder) 65 hp. when we took it out initially, it would only run 24mph on the gps. I found out the prop was a 14x11, so we switched it out to a 13x15. Now it is running 29 on the gps, and it will get a little better when the rings are fully seated and we cut back on the extra oil in the gas. Sounds like you are expecting too much from the setup you have.

Craig Moore
Mancelona, MI