Re: Merc 150 1990 xr-4 power
Hi, I'm just wondering what kind of speed y'all are getting out of these outboards. I have mine on an 18ft ranger fish n ski - not sure what it weighs but do know it holds 7 occupants. If I remember correctly the rpms were around 5300 wide open. It has a 5 blade stainless prop - not sure of the pitch rite off. Anyway I can only get about 40 - 42 mph. Is that normal? The engine starts, idles, runs, and sounds fine.
Under what conditions are you getting these results? Is that true (GPS) speed or off the water driven dashboard speedometer?
I have an XR4 on a 1988 Tracker fish-n-ski. I run a 24 pitch high five when I'm hauling 2 fat fishermen to work, and it goes about 60 at 5900 rpm. Alone in the boat, 1/2 tank gas, livewells dry, it runs in the middle 60s at about 6200 rpm. When I'm hauling family on ski-play patrol, I put on a 22 pitch high five, which will do about 55 with a full load at 6000 rpm.
There are many things that could be wrong. My boat was a 50 mph slug with the 22 pitch prop on it, barely running 5900 with just me in it. There were fuel delivery issues, link n sync was off in several places, carbs were all a little misadjusted, engine height on the jack plate was wrong, and the boat had some water in the wood and foam.
That engine likes to run near 6000 rpm. It has an advance module on it that could be acting up, or not working at all. It should advance the timing a few degrees at 5000 rpm.
If it is stock, it has a 4 1/4 inch lower. A lot of them lost the lower and a 4 3/4 in was installed in it's place. The prop manufacturer and part number would help figure it out.
That motor was sold as a bass boat special, and puts out over 160 hp right out of the crate. It is limited in what you can do to improve it, with around 175-180 being the limit.
hope it helps
John
