Mercury 150 xr6 2003 issues

[robsalik24]

Recently acquired a 1992 Bayliner rendezvous with a 2003 Mercury xr6. Motor has less than 50 hours on a rebuild 6 years ago. My Max RPMs I am hitting is 3200 RPM with a 16 by 13 pitch ptop. First big engine outboard I've owned. I have replaced ...fuel filter, fuel lines, fuel bulb, and spark plugs. Engine starts rough but once is warmed up runs and idles great at 500 RPM. the prop size comes from Mercury based on weight and loading of boat with a 40 gallon tank. So why am I not exceeding 3200 RPM at wide open throttle? I am mechanically inclined but, I am hitting a wall and I could use some advice from some pros. Boat runs on premium fuel only.

 

[Chris1956]

I doubt that motor idles at 500 RPM. That would suggest your tach is inaccurate. See if it is set to 12P or 6C on the back.

What kind of boat is that? Quick search says 26 footer.

 

[robsalik24]

Brand new Faira Tach set at 6C. It's a 26ft Bayliner deck boat. Boat weighs 3300 lb, motor weighs 403 lb. Max Rev on motor is 5600 RPM.

 

[robsalik24]

Huh I just took a photo of it from the back side and you may be right! my tach may be set incorrectly. There is a photo of my profile tell me what you tthink.

 

[Faztbullet]

Xr6 should have the smaller lower unit as prop size should be more like 13x16

 

[robsalik24]

Large OB 135-200HP 1.87 Gear Ratio

 

[Faztbullet]

If it has a large gearcase 1:87 lower it has been changed as original was a small diameter 1:78 ratio

 

[robsalik24]

I have the original owners manual it states that it's a 1.87 gear ratio.

 

[Dukedog]

Xr6 should have the smaller lower unit as prop size should be more like 13x16

little gear case went away in '96/'97 I think Faz….maybe '95?

 

[Faztbullet]

Did some searching and found it was 97-98 that Merc went back to big case and supposedly lil case it could be ordered as option...

 

[Dukedog]

justa "foggy 'ole brain".. that's tha main case I used on most all my hot rods when I was inta that "sickness".. know they were gettin' hard ta find when I finally got away from it....

 

[robsalik24]

Just an update....My Tach was set incorrectly. I am turning 6300 at W.O.T. with 16 by 13 pitch prop. Running a motor at 5200 RPM. I am up on plane but seem to still have a little bit of water running through the hull. Like the ass of the boat is still to deep. Or is that normal for a tunnel Hull/ fiberglass pontoon boat?

 

[leonreno]

If your wot is 6300 rpm you need a new prop, you need more pitch. Some where in the 15-17 pitch area. Also may need to check mounting height of motor. Might be too low. What prop did you buy?

 

[robsalik24]

Leonreno.... I currently have a 16 dia x 13 pitch recommended by Mercury for wieght and fuel load on boat. So obviously that's too small. As for height of the motor I am unsure on this.

 

[leonreno]

The cavitation plate typically needs to be about an inch above the bottom of the hull but I don’t know about your boat as I believe it’s a cat / tunnel hull. The cav plate should be just out of the water when on plane near WOT.

 

[robsalik24]

Okay..... sounds like I have some work to do.