Nitro Bass Boat Planing Issues

[codybuehler]

I have a 1998 Nitro 884 savage (18' 3") with a 150 merc 2 stroke outboard. I have been having planing issues since I bought it in June. With the motor trimmed full down, the boat goes nose high, and takes forever to get onto plane. Once on plane, it takes off with no issues. It came with a SE 200 hydrofoil, which based on . It has a quicksilver 21p stainless 3 blade prop.

This past weekend, The boat wouldn't go onto plane with 3 people and a full gas tank. I had one of my passengers sit on the front deck, then the boat went on plane. It is very, very frustrating having a boat that can't get on plane, especially with a 150hp (max for this boat is 175hp).

I put this post in prop questions because I have a feeling the pitch is a little low at 21. would a 23 or 24 give me the lift and push I need to get on plane in a reasonable manner? I'm not looking to get the fastest possible speed out of this boat. Right now it can do 54 mph WOT @ 5850 RPMS, but my usual cruising speed is 30-40mph. I'm happy with that.

Here are a few more fun facts that may help: The boat is outfitted with an automatic bilge that does move water (I have a leaking fitting associated with my livewell and it's only 2-3 gallons per 45 mins, but that's another issue). The boat has a 40 gallon tank, I do have a jack plate that is full down, 3 batteries, 2 chargers and no way of moving anything forward due to space limits.

Any thoughts, ideas or suggestions will be a great help! I am in the process of borrow 2 24p props, 1 tempest and 1 Bravo 1. I am hoping for dramatic results, but I'm not holding my breath.

Cheers All and thanks!

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

A bigger prop (more pitch) will make the holeshot issue worse. At 5800 rpm (if the tach is right) your holeshot should be just fine. I'd start by making sure the motor is running right at low rpm (good spark & compression). If that's OK I'd take a look at set up.

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

A bigger prop (more pitch) will make the holeshot issue worse. At 5800 rpm (if the tach is right) your holeshot should be just fine. I'd start by making sure the motor is running right at low rpm (good spark & compression). If that's OK I'd take a look at set up.

Good to know. I am going to replace the plugs very soon. They came in the motor, and I have no idea how old they are. The motor runs like a champ right now. Idles well and runs without a glitch. I am tempted to throw the compression gauge on it just to see what that says.

The jack plate does have tell-tale marks that it was in a few positions higher than what it is now. Would moving the motor up help in any way with the planing issue? I'm new to the whole boating world. I'm thinking that's what you mean by setup.

Thanks!

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

Sounds like a manual jackplate (which is fine) but yes, play with the height by all means. We'll assume it has about 5-6" of setback, right?

Next - does your current prop have vent holes?

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

Sounds like a manual jackplate (which is fine) but yes, play with the height by all means. We'll assume it has about 5-6" of setback, right?

Next - does your current prop have vent holes?

I'd say the jackplate does have 5-6" of setback. I plan on setting it where I can see it was set before and trying it at those points. I'm thinking it got set full down at the shop I bought it at after the previous owner traded it in. I did notice some forward spray coming off the motor that didn't seem quite right. Another clue it might be too low, should the hydrofoil be visible while at planing speed?

As for the prop vent holes, It does have them, but I'm not sure how many, placements or sizes. I have no way of checking until friday on that. I just know it's a quicksilver prop with the numbers 48 11070 A40 21P on it.

 

[Mi duckdown]

Re: Nitro Bass Boat Planing Issues

remove the hydrofoil and retest. Pics of the transom set up would help ALOT

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

remove the hydrofoil and retest. Pics of the transom set up would help ALOT

I will get pics as soon as I can.

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

At this point I'd make 1 change at a time. So far You've been establishing a baseline with it on. I'd leave it on for the moment and play with height. The setback is fine. Don't worry a lot about if you can see the fin or not, not real important since we're all the way down and testing up in small increments.

 

[steelespike]

Re: Nitro Bass Boat Planing Issues

Thats a good point ^ one change at a time, though
occasionally its possible that a foil will actually dig a hole as you try to get out of the hole.

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

I put some thought into the whole issue last night, trying to rack my brain with how exactly it acts. Here are some more clues:
1. It does bog down when I initially take off full throttle like it is grabbing too much water and is having a hard time pushing. It's not bogging like it would for a firing/fuel issue. It feels the same as trying to move a car in to high of a gear.
2. Once it starts picking up speed and getting out of the hole, It still has to work pretty hard until minimum planing speed (which is ~17-18mph)
3. full down trim is actually pointing the prop down at ~15-25 degree angle below level. On plane, I found trimming up slightly (about 1/8 of the trim gauge up) helps. I think this is normal, but I'll let someone with more knowledge tell me so.

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

Classic description of excessive drag. As you raise the motor you'll lose drag and gain efficiency. How high you can go will depend largely on the prop technology and condition.

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

Classic description of excessive drag. As you raise the motor you'll lose drag and gain efficiency. How high you can go will depend largely on the prop technology and condition.

That's a relief. I was thinking it was going to cost a fortune more. I am beginning to think BOAT means "Bolt On Another Thousand"!

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

That's a relief. I was thinking it was going to cost a fortune more. I am beginning to think BOAT means "Bolt On Another Thousand"!

It might, but not yet.........

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

It might, but not yet.........

geee, thanks!

 

[cajunmerc]

Re: Nitro Bass Boat Planing Issues

what merc 150 is it ? that's what we need to know ? nitro 's are hard to launch,what is the diameter and model of the prop on it now ? what is your prop to pad measurement ? is the merc a '98 too ? carb xr6? efi 2.5 liter ? have you checked to see if your throttle cable is adjusted properly ? need lotsa info. your motor is way too low if all down on a 6" plate. with 3 guys in the boat,and full wells and gear your gonna be looking at a 4 blade 21 or a 23 trophy plus repitched to a 22 to launch that weight and still hit 5600, the only 3 blade that will launch and pull hard to the rpm you need will be a cupped 21 tempest plus,your asking it to do alot on a heavy boat.really,that boat should have a 200efi w/24 trophy,and yes,that wing thing should be way out of the water on plane,learn how to measure prop to pad,and start at 3.5" and adjust up from there,

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

So...Just got back from running the motor with the jackplate up ~2" from dead bottom and what a difference. It pops up on plane in about 5-6 seconds now compared to 15-20 before. WOT left me at 54mph at 5200 rpms. Up 2 mph, down 600 rpms. I can stand to raise it another 1/2" - 1" and should be able to still see results.

I attached pictures of the jackplate and motor side shot. The jack plate was buried all the way to the top of the slots.

I'm sure I could change the prop for different results, but that's nitpicking, the expensive way.

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

Excellent, this is why we harp on set up rather than buying a prop right away. Yes, we'd love to sell a prop but not at the expense of someone not getting efficiency. Always max out what you have first.

As an example we had a guy in the shop last week that wanted to buy a prop with less pitch (needed rpm). He was convinced from reading on the web it was his only option. The motor was fine, we looked at that first, moved the motor and in the end he gained the rpm, speed and efficiency he was after without buying a prop. In fact when he does get a new prop it'll most likely be one with more pitch. He went from the low end of the rpm band to the top of the band, boardering on actually needing more pitch.

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

I was very relieved, but it could use some more tweaking yet.

The higher I go with it shoud lead to less drag, higher rpms and more speed. How high should I go if the previous sentence is correct? I know that when the prop cavitates and I overspeed the motor that I went too far. Is there a happy place of borderline cavitating that the prop gets a bit of air to bring up the rpms, but still able to catch enough water to push effectively? Is this where a higher pitched prop would come in?

And cajunmerc, you were all over the place with the props. My boat is only rated to a 175hp max, so the 200 with a 24 trophy is out. You mentioned 4 different props that would work, and they really aren't anything like each other. I am really swaying from changing the prop from a 21p based on the latest run. 3 people, with gear and water in the wells popped right up now that I raised the jackplate. There is no way I'm buying 4 props and repitching one just for testing.

 

[Dhadley]

Re: Nitro Bass Boat Planing Issues

How high you can go will depend largely on the technology built into your prop and it's condition. But yes, you have the basic concept right.

 

[codybuehler]

Re: Nitro Bass Boat Planing Issues

How high you can go will depend largely on the technology built into your prop and it's condition. But yes, you have the basic concept right.

Fantastic. Thanks for all your help so far!