Nitro Z6 Motor Problem?

[jerry shack]

I did the best I could with the pics. Not sure which part of the hull should line up with the cavitation plate. The lowest part of the hull in the center of the boat (Bottom of Hull 1 pic) is about 2-1/2" below the cav plate (Hull 1 to Cav Plate pic). The larger/flatter part of the hull is off to the side about 8" (Hull 2 to Cav Plate pic) and best I can tell is about 3/4" below the cav plate (Hull 2 to Cav Plate pic). Does it look like there's room to lower my motor without developing too much drag?

DJRazorback,
The pic's are fine, as far as where to put the straight edge it would be the very center of the pad. However how much set back is built into the hull?(that's the distance from where the motor is mounted to the pad) Ruel of thumb is for every 1" of set back you come up 1/2". So if you have 4" set back the motor goes up 2". That's called a starting point. Looks like from the pic's you may have to much height. Do the formula with set back included you might have to go down 1/2-1".

 

[jerry shack]

The grommets helped my 225 Merc. trying to get up on plane the prop would just spin from to much air/ bubbles or what ever. With the grommets I can tell the difference when trimmed and on plane.

Birda40,
Glad that helped.

 

[byron cooley]

Your measurements mean nothing.
Z6 is a pad hull, you need to forget about cavitation plate. Need to measure center of propsshaft to pad.

 

[DJRazorback]

byron cooley - here are pics of the lowest point on the pad in relation to the center of propshaft (Pic 1 & Pic 2). What does this tell me? Too high? Too Low? Just right?

Jerry Shack - I've done a good bit of research on setback and I'm not sure how much setback (if any) my Z6 is set up with (Pic 3, Pic 4 & Pic 5). Looks to me like there is 0 setback. Please let me know what you think or if you need different pics.

I changed the lower unit oil and it looked fine, no metallic look or metal filings. So I'm back to the lake tomorrow to move some weight around and see if that changes anything. Also going to try removing the Hydrofoil. The closest lake that I can get the boat up on plane is 1-1/2 hours away so I can only try different things on weekends. That's the reason it is so long between post.

I really appreciate you guys trying to help!!

 

[jerry shack]

byron cooley - here are pics of the lowest point on the pad in relation to the center of propshaft (Pic 1 & Pic 2). What does this tell me? Too high? Too Low? Just right?

Jerry Shack - I've done a good bit of research on setback and I'm not sure how much setback (if any) my Z6 is set up with (Pic 3, Pic 4 & Pic 5). Looks to me like there is 0 setback. Please let me know what you think or if you need different pics.

I changed the lower unit oil and it looked fine, no metallic look or metal filings. So I'm back to the lake tomorrow to move some weight around and see if that changes anything. Also going to try removing the Hydrofoil. The closest lake that I can get the boat up on plane is 1-1/2 hours away so I can only try different things on weekends. That's the reason it is so long between post.

I really appreciate you guys trying to help!!

In Pic #1 the set back is from the hull plug straight up from there, now measure the step straight back to the end where the motor is mounted. From the pic it looks like about 4-6" of set back . There fore at 4" between the straight edge and the bottom of the cavitation plate should be 2" for an example. If it's more then 2" lets say 2 1/2" the motor would have to come down 1/2 " like maybe 1 bolt hole for a example. Remember this is your starting point.

 

[byron cooley]

How to measure

 

[byron cooley]

My 05 Nitro 640LX runs and handles best around 4 1/2" prop to pad. Very similar boat to yours.
I have a 75hp opti with 90hp computer and 90hp throttle body restrictor.
50-51 [email protected] 5760rpm by smartcraft monitor with just me 205lbs, gear and 1/2 tank of gas.
2000ft altitude and Lazer II 22p with added cup. 3 large plugs in prop.
Holeshot just a couple seconds

 

[DJRazorback]

Byron and Jerry - awesome info from both of you. Thanks!

Byron - I’m running a Laser II 22P as well. I’ll use the info you provided to see where I’m setting.

Jerry - I’ll run the setback measurements as well.

Surely between the two I will get it figured out. I’ll get back with you guys. Thanks again!

 

[DodgeBoy]

Well if you added batteries and a trolling motor to the boat the extra weight is the problem. You will need the play with the trim to find the sweet spot. When by myself the boat will top out at 56 add a few people, ice water in the live well and she is a totally different boat. You need to adjust your trim anytime you change your weight in the boat.

 

[Z-Man 21XL]

I do not feel your issue is prop or engine height related. It sounds as though you have changed something as far as loading/weight distribution is concerned! I would be more concerned that the boat only runs 40 mph at 4000 rpms. This is not even close to the recommended rpm range of the motor. You need to have the motor checked out as to why your not getting wide open throttle. Your issue is definitely not hub or PVS plug related. A hub either works or it doesn't. When a hub goes bad you'll know it because the prop shaft will spin and the prop doesn't (May idle but not above that)! PVS plugs play no role whatsoever once the boat is up on plane.

 

[DJRazorback]

Hi Z-Man,
Thanks for the feedback. I think I have figured it out. I actually feel really dumb that I didn’t figure it out earlier. Back before this all started I mounted my new Humminbird transducer below the bottom of the pad and evidently it was disturbing the water in front of the prop. I finally noticed it by a narrow rooster tail shooting up along side the motor. So I temporarily removed the transducer and it was back running like it always has. I have since remounted the transducer in a better location and will know next weekend if it is permanently fixed.

WOT on my motor is around 5700 rpm (I think) and the motor sounds fine. I just don’t run it that way often (ever actually), so my reference point was 4000 rpm on smooth water and trimmed properly always gave me 40 to 45 mph by gps. That was before I converted to a 24v system, new fish finders, and Terrova trolling motor. Hopefully the problem is solved and I’m permanently back to my comfortable cruising speed.

Thanks again to everyone who responded and helped. I love this forum.

 

[Z-Man 21XL]

Thanks for the update--For future reference when asking for help for motor/prop related issues, always state WOT numbers. This allows someone to assist in troubleshooting your problem. By the way I see you're in Memphis. I am originally from Arkansas (close to Jonesboro) and worked for the Arkansas HIghway Police as a Safety Investigator for a few years. I sometimes worked at the scalehouse on I55 just across the bridge doing truck inspections.

 

[DJRazorback]

10-4 on the WOT info in the future.

I grew up in western Arkansas. The lakes there are awesome. We go back every chance we get. Did you get a chance to fish any of highland reservoirs while you were there?

 

[Z-Man 21XL]

After I retired from the Army and moved back for a few years I fished all over the state. Dardanelle is my favorite lake.

 

[DJRazorback]

Ouachita is my favorite. In fact, I’m taking my adult son there this weekend to fish for a few days and see if we can catch the black bass schooling. I haven’t fished Dardenelle in years. I’ll have to plan a trip there soon.

Harker Heights, isn’t that just outside Temple? You’ve got some good lakes around there too.

 

[Z-Man 21XL]

Yes, I'm in HH---Stillhouse Hollow is in my backyard