Prop sizing

[yorkserv]

I have a 1988 merc 200 black max on a 1974 mako 20' I am attempting to make a good decision on a prop but I just got into the mechanics side and decision making of boating so i need some help. The boat right now is going about 49-50 mph at 6000 rpm that is through my gps. Now a buddy of mine had a p21 clever prop at his house that is hubbed for merc so he gave it to me.is that not enough pitch? should I try it? and if not what size should I go to and what manufacturer? Thank you for any help i can get!!

 

[JB]

Re: Prop sizing

Howdy, Yorkserv.<br /><br />Welcome to iboats. <br /><br />What prop are you using now to get 50mph at 6,000rpm?

 

[Laddies]

Re: Prop sizing

Go a head and test it or give us the pitch of your old prop, your old prop is close to the right RPM range watch your tach to make sure the engine don't over rev

 

[yorkserv]

Re: Prop sizing

i really dont know i am going to my friends house to check so i can change the prop

 

[yorkserv]

Re: Prop sizing

Laddies <br /><br />about what rpm do you suppose I should not go over

 

[Coolmaker]

Re: Prop sizing

WOT (wide open throttle) on the engine is 5600 rpm

 

[achris]

Re: Prop sizing

Hey guys..... I think he said Cleaver prop..... Correct me if I'm wrong, but ain't they surfacing props? <br /><br />If the engine isn't set up for surfacing props, then you're going to run into all sorts of interesting things if you put it on. Let us know what happens, I'm curious.<br /><br />Chris...........

 

[yorkserv]

Re: Prop sizing

What kinda problems are you refering to I really like this motor and i want to keep it as long as its operating the way that it is<br /><br />And thanks for the help and input guys

 

[yorkserv]

Re: Prop sizing

the prop pitch that is on the boat right now is a p17 and i have to get a bigger thrust washer to put the prop on

 

[yorkserv]

Re: Prop sizing

THe prop that i have on the boat right now is a p17 do you guys think that it will work. One more thing about the tune up how often would you guys reccoment to change the plugs on the motor,

 

[plumber2]

Re: Prop sizing

I have a 17 1/2' boat with a 150 Black max xr4 running a Laser II 24p that is perfect. But it is a lot lighter boat. If you are running 6000 rpm's now wide open then you need more pitch. Probably only one more than you have. You want it to run between 5200 and 5600 at full throttle.

 

[yorkserv]

Re: Prop sizing

thanks plumber2 i gave up on the clever prop the thrust washer that i picked up is .010 of an inch to small so i am just going to get the prop that will make the boat work better. What affect do you think going up to an 18 from a 17 have on speed and performance