Prop for '88 Mercury XR4 150 - Need help

[achilles555]

I would like to trade my current prop for a new one. The previous owner of this boat says that the Quicksilver Laser II that is currently on there barely gets her out of the hole. In talking with others about my boat, it has been suggested that I go with a "High Five" Prop. Any help you guys can give me as to what prop I should look for, and maybe a place to find it would be greatly appreciated.

Here are the details of the boat:

Boat: 1985 Charger Bass Boat
Motor: 1988 Mercury 150 XR4 Black Max
Current prop: 21 Quicksilver Laser II
Length: 20' 8"
Weight: 1400 lbs.
Use: Bass/Crappie Fishing and some Family Fun (skiing, tubing)

You can see the boat, motor, and current prop here: http://s286.photobucket.com/albums/ll117/acleme1/

I don't need anything extravagant. Just a prop that will pull skier's up, and get me on plane. I won't hardly ever open-up the throttle. Mostly I will keep it at a nice cruising speed when going from one fishing hole to the other.

Just a note: I'm a rookie with boats and motors. This is my first restoration project, and I am trying to learn as I go. From reading this forum, I realize that I need to get her out on the water and check RPM's to get a good read on what prop I need. I'm not even sure that the RPM guage works on my boat yet. What do you guys think would be the best prop for this boat. Thanks SO MUCH for the help!

 

[Silvertip]

Re: Prop for '88 Mercury XR4 150 - Need help

You answered part of the question already. Since you have no experience with the boat, you have no idea what rpm the engine runs at when at wide open throttle, so you therefore don't even know IF you need a different prop. Make some test runs at wide open throttle with an average load. Note the RPM. That's the crucial number. Then and only then can you determine if you have the right prop or if you need a different one. The fact that you don't plan to run wide open has nothing to do with prop selection. If the prop is wrong at wide open throttle, its wrong at any speed less than that.

 

[achilles555]

Re: Prop for '88 Mercury XR4 150 - Need help

thanks for the reply silvertip. i'll get her out and take some detailed notes. i'll report back once complete (although it might be a month or so). thanks again.

 

[achilles555]

Re: Prop for '88 Mercury XR4 150 - Need help

btw silvertip,
where in the midwest are you? i am in the kansas city area.

 

[BF]

Re: Prop for '88 Mercury XR4 150 - Need help

just as a comparison FYI... I have a V150 that is a few years older than your XR4... mine is on a 16' fiberglass ski boat (like glastron CVX). Which I imagine is lighter than your 20 footer. I have a 19" pitch aluminum prop on it, and it goes to 6K rpm at WOT, and does mid 50's... It jumps out of the hole and accelerates fast. No problem pulling skiers or multiple tubes. Boat still jumps out the hole with 5 people on board.

It's possible I could do better with a bit more pitch (?), but I'm guessin' that since your boat is bigger, a 19 pitch would work better than the 21 that on it has now (?). As you said, best to try it yourself first and see how it works. If it's slow out of the hole with a lightish load, it'll probably be a dog trying to pull stuff.

Another option if your WOT rpms are good, but it's slow out of the hole, you might research adding some ventilation holes (if the prop doesn't have them already). On start up, they allow some exhaust gas to flow behind the blades allowing the motor to ventilate a bit and get the rpm's up.

I've had no direct experience with a high 5... but my neighbor had one on a 200 hp merc and loved it.... until someone stole it off his motor over the winter. He replaced it with a different brand, I don't know what, and complained that it was noticeably less-good. Whether his new prop is the optimum pitch etc, I don't know either.

anyway, good luck with the new boat. Nice rig.