Thread: Prop question on 2002 merc 200 efi engine

yep, cobra was a good boat. Go over to bbc and ask the cobra forum. Im sure someone will be able to answer what prop to use. But with what you posted the 25 should be the correct prop.
Also good advise on the impeller.

I just received an IM from someone on bbc. He has the same boat and a 25 tempest but his was blueprinted. He is running with 2 plugs out and his prop to pad is 3-1/4 below. He said a great hole shot with a tournament load. Hope this helps.

he was seeing gps speeds of 69 with the boat loaded fairly well. 67 full wells and fuel and 2 people

Well, guys, not sure what to say especially about the response from bbc. my boat wont powerload and thats not acceptable period. Ive had 90hp boats with more ass than this thing down low. My uncles boat is the same way loading but were always together so I can back the trailer to the boat while he is on the throttle and he has a 21 ft hawk with 225 efi merc. these motors are sorry on low end in my opinion but I hear there great motors so we will see.

My boat is running 5500-5600 rpm now fully loaded and the best speed I get is 59. Now with that being said, I was getting 63 when the jack plate was up 3/4" but I was losing water pressure so had to do what I had to do. What is acceptable for lost water pressure when trimming up. That boat today would get up to 18lbs and at full trim it falls to 12lbs? When the motor was still up 3/4" it would fall to 8lbs.......

We have a tri-hull boat that we use for catfishing that has a suzuki 115 on it and when loading on the trailer and you up the throttle it will flat rip up in the rpms and push itself up to the rubber roller with ease but this small bass boat of mine with a 200merc wont?

As for the water pump, When I bought the boat supposedly they did a tune up to the boat before I picked it up which consisted of lower unit oil change, plugs, water pump, and im sure im forgetting some stuff ALTHOUGH I couldnt tell you how respectable this dealer is that I dealt with so for all I know maybe none of it was done.

If you have all the plugs out on the PVS plugs you may be getting too much venting not allowing the prop to bite enough and push the boat up on the trailer. This will also cause a crappy holeshot. Guys have the issue sometimes with the Trophy props due to the fact they are a small tube type prop and exhaust over the prop barrel and also out of the PVS holes. The cure for that is a diffuser ring. Since the Tempest is a large barrel you only vent through the PVS holes and of course, out of the rear. If you are getting too much venting the prop won't bite enough on the low end and give you the thrust you need. You might want to try a couple of medium plugs to see if it helps. You can mix and match plugs too, i.e. one large and two medium. The PVS venting only affects holeshot and thrust on the bottom end. Once you are up and running at speed the water is rushing over the holes so fast it basically seals them off.

Originally Posted by Slab Junkie

If you have all the plugs out on the PVS plugs you may be getting too much venting not allowing the prop to bite enough and push the boat up on the trailer. This will also cause a crappy holeshot. Guys have the issue sometimes with the Trophy props due to the fact they are a small tube type prop and exhaust over the prop barrel and also out of the PVS holes. The cure for that is a diffuser ring. Since the Tempest is a large barrel you only vent through the PVS holes and of course, out of the rear. If you are getting too much venting the prop won't bite enough on the low end and give you the thrust you need. You might want to try a couple of medium plugs to see if it helps. You can mix and match plugs too, i.e. one large and two medium. The PVS venting only affects holeshot and thrust on the bottom end. Once you are up and running at speed the water is rushing over the holes so fast it basically seals them off.

Slabjunkie, appreciate your post here but I may have your confused. The reason why it isnt pushing its self onto the trailer is because its dogging rpm wise. When I go to load it on the trailer and the boat starts to walk up the trailer i start to gass it up and it simply wont come up in rpms at all. Stomp the hotfoot and it simply boggs at about 2300rpms. Thats Why I wanted a smaller pitch prop so it has the a$$ to spin that prop over. With the 25 pich I have now I have taken all the plugs out and while it did help some on the take off it still didnt help at all with loading on the trailer.

When taking off from dead stop it comes up on plane pretty good and soon as it plains out you really hear that motor get pulled hard because the prop is biting so hard. It just seems to me the prop is to much for the boat. Im no brainiac on this stuff though.

I think your thinking that the motor is coming to full rev trying to gas it up onto the trailer where it is the exact opposite really. Just simply doesnt have the power to get the motor to its "powerband" . Its right there though man. I think of that thing would come up another 500 rpms pushing on up the trailer the motor would spike the rpms and fly right up on there.........

Originally Posted by sliderman

Sounds to me like it's propped out correctly. Try raising the motor height one inch and hold on.

x2

Also--go to the mercury web site--you can play around with the numbers to see what you get. Typically going from a 3 to a 4 blade you want to drop 1p (you still keep the same RPM) I run a Yam. pro v 25P 3 blade on a 150 XR6 (18' boat). Hole shot is great--even on a full load and turns 5600RPM runs 58mph when trimmed correctly--too much trim my RPM goes up but no more speed. So a 25P I would think would not be too much prop (I've been told it was for mine but any less I run way too much RPM) Also iboats.com has some very good info on the forum about prop selection--you can search them. Just my 2 cents. Hope it helps.