Is my prop causing me to fall short?

[honda460ex]

I bought a '97 Glassport 17' Fiberglass Bass Boat back in January. It isn't planing out like it should. I have a '83 Mariner 115hp Inline 6cyl on it. When I get up to full speed I am running flat in the water. My nose will not rise so I have a lot of drag. It has a Hydrofoil on it from the previous owner and goes on plane quick, but once up it stays their. When trimmed up much the motor seems to catch air and definitely will not lift the front. Also the trim fights me when I am wide open. It does NOT like to trim up when under a load like that. I usually have to trim it up before I get to the faster speeds because of this. So what gives? Why can't I get the front end of the boat any higher? Is it my prop? Hydrofoil? Is my motor not in the water enough? Or is it in the water to much? I have included a couple pictures of how the motor sits in the rear when it is level with the boat. The top speed I have hit with me and all of my gear is 45mph and that was a GPS reading so i know it's accurate. The boat itself is a very light hull and very shallow for a fiberglass bass boat. Everyone that sees it swears it should fly for what it is. Any help would be GREATLY appreciated... Thanks.

 

[Texasmark]

Re: Is my prop causing me to fall short?

Didn't you post this question elsewhere on the forum, like in the boats section? Double posting is confusing. Your first picture and boat mentioned seem familiar.

Mark

 

[steelespike]

Re: Is my prop causing me to fall short?

Removing the foil is a goods start.Losing the foil may help the up trim problem.
Read the stickys at the top of the page.
Try to answer all the questions. Get us a comeplete info on the results of a test run(s).

 

[ufm82]

A couple things

A couple things

1) Yes, dump the foil. Once the boat is up it shouldn't even be in the water. if it is that's a ton of drag and will actually pull the stern of the boat down when you trim up.
2) While you have an SS prop I can't tell what kind. You sound like you need bow lift- a cupped blade will do that. Laser II and Tempest props will give you the lift you are looking for.
3) Can't tell from pics where the engine is very well. trim it level with the keel and see where the anti-ventilation plate is in relation to the keel. 1"-1 1/2" above the keel is desired.
4) Do go to the sticky and look at the necessary info- all those details will help us determine potential causes.

UFM82

 

[honda460ex]

Re: A couple things

Re: A couple things

Sorry Mark, I did post something similar elsewhere. Someone there recommended I post here for help with the prop. Sorry for the confusion. I'll look at the stickys, post more info, test it this week, and let everyone know. Thanks all.

 

[honda460ex]

Re: Is my prop causing me to fall short?

Ok, here is the model of my current prop; Quicksliver 48 72500 A5 21P and it is a stainless steel prop

Now can you tell me what any of that means? I know the last number 21P is the pitch.

I found a website that has a prop calculator. It tells the factory weight of my boat, the motor weight, add in # of people, gallons of fuel, and estimated gear weight which I placed at 400 lbs and it recommended a 23P prop for speed and a 21P prop for watersports. Sound about right?

By what they say my boat only weighs 800lbs, my motor 375lbs, two people at 336lbs, totally full fuel weight at 117lbs and gear weight at 400lbs. Total of 2028lbs overall weight with those figures. It has my WOT RPM's at 5,635 and says I should be able to obtain 52.76mph. But very rarely will I be geared and fueled quite that heavy. It also recommended an aluminum prop in the 23P, not a stainless steel. Advantages? Disadvantages?

Does this all seem like it could be part of my issue with planing out along with the hydrofoil? Sorry for all the questions and detail but this is all new to me and I like to know details.

 

[Sprky]

Re: Is my prop causing me to fall short?

From the pic, your motor appears to be to high.

I have worked with a lot of set ups (sprint, pro craft, cajun, stratos) where when the motor was dropped, leverage was gained and bow lift was available.

Try dropping the motor as low as it will go then work up. The mercury props do not have the rake to carry your boat when jacked up. A raker prop (omc) will work at your height and higher but will have to be rehubbed for a your application.

Chris

 

[ufm82]

Re: Is my prop causing me to fall short?

Personally I don't like the Quicksilver props. They don't have the geometry that is needed for your needs. I prefer the true Merc line. And yes, they will have the rake you need. In fact, props like the Laser II and Tempest props (3 blade) and the Trophy (4 blade) are made for applications where bow lift is desired. If you look around, you'll see most bassboats that are Mercury powered will run Tempests or Trophys. The Laser is designed for fully submerged applications like on bowriders. The Tempests and Trophys will run high and even pierce the surface and will perform. And a Merc prop will fit without any changes- simply use the Torque Flo hub kit and you're off.

Bear in mind that there are a myriad of props made by manufacturers. Merc makes several models and they don't fit everything. The Vengeance prop was awful on my boat. I have a Mirage that is great for pulling loads like tubes but has no bow lift and my boat will porpoise bad if I try to trim it up. I ran a Laser once to test it and it blew out on me when i trimmed up high. I now have a Tempest on my boat and it does great. I get plenty of bow lift and you can feel it when I start to trim up. The bow comes up, the speed and RPM climb and at WOT I run 51 mph with a cowl-high rooster tail. Your boat would do very well with either a Tempest or Trophy but they are not interchangeable performance-wise.

 

[honda460ex]

Re: Is my prop causing me to fall short?

Well I tested it out this last weekend and you all are right. The motor is to high and the prop isn't helping either I believe. The hydrofoil was keeping me from trimming up but helping it come up on plane quicker. When I trimmed up without the hydrofoil it blew out of the water and definitely didn't lift the bow. I am prop illiterate. So any places or ideas to get a good prop for a half way reasonable price is appreciated. I know the stainless steel props are pricey. I am going to try and drop the motor a little by reworking my trim plate. Don't know if my idea will work but it will probably take me a week or two to get it done. I'll up date as I figure more out. Thanks all!

 

[Texasmark]

Re: Is my prop causing me to fall short?

When I trimmed up without the hydrofoil it blew out of the water and definitely didn't lift the bow.

I never experienced "bow lift" till I bought my '89 Ranger Fisherman. It was a "pad" hull and I had a high rake SS prop on it. I normally hole shot with the engine near vertical to the boat (0 trim) and as I cleared the water on the hole shot, without touching anything else, I started trimming out. You could clearly see the bow lift up over the water (after it had laid down from the hole rising) and the spray moved from just ahead of the helm to coming out the aft quarter (even with the corners of the transom), and accordingly, mphs just kept rising as did engine rpms. That was quite an experience. I could trim out on that rig till the prop actually started coming out of the water and the rpm's started climbing and the mphs started falling.....but that was at 50 mph with a 115hp OB.> I loved that boat and Son-in-law has it now.

Mark

 

[honda460ex]

Re: Is my prop causing me to fall short?

That's awesome... Hope I can accomplish close to that with my boat. Like I said, I am prop illiterate. Do you think a Raker 22 pitch prop then would be a good fit? I found on on ebay a Raker Prop that I thought I could take a chance on. It is a 15 spline and so is my motor. But here is my question, like I said, I am illiterate about props. Will any Raker prop work as long as it isn't to big inch wise and has the right number of splines? And if the splines are wrong can I have someone press the old hub kit out and put a new one in to fit the splines on my boat? I know I bought a prop the other day because it was cheap enough and a quicksilver, which at the time I thought might help me but obviously not. The outside of the prop is to big for my lower unit. The splines fit, but the prop diameter is to big to slide inside of my lower unit at all. It hits the outside. Lol, I need "Prop Class 101".

 

[honda460ex]

Re: Is my prop causing me to fall short?

I also found a Laser II for the same price as the Raker on ebay just now, but on I-Boats it doesn't list the Laser II prop as fitting my motor. So how do I make one fit?

 

[Texasmark]

Re: Is my prop causing me to fall short?

I also found a Laser II for the same price as the Raker on ebay just now, but on I-Boats it doesn't list the Laser II prop as fitting my motor. So how do I make one fit?

I was under the impression that the Laser is a Quicksilver prop. Quicksilver is the accessories name for Brunswick Marine who also make Merc and Mariner. Guess you have to go to them and ask the question. While there ask if not, what is the Laser equivalent that will fit your Mariner.

What you want to get the bow up is a high "rake" for bow lift, cups for digging in and not ventilating in turns and rough water, SS for longevity if rocks aren't a problem, and ports if you want a fast hole shot and high mph both. So, regardless of the name/mfgr, that is what you want to shop for....then the only thing you need to do is to get the pitch right and that could take some experimenting which translates to: buy from a dealer who will let you try a prop and if it doesn't work, and you give it back in the condition in which you received it, he will give you another to try. Costs more, but once the money is spent, you have the life of your boat to enjoy and the money is long gone!

Mark

 

[Sprky]

Re: Is my prop causing me to fall short?

The raker you are looking at is for a large gear case. (4 3/4 dia.) Do not buy it! Your case is a 4 1/4 dia.

Find an old OMC SST 21 pitch prop that fits a V4 and have it rehubbed for your mercury............or drop your motor.

The QSS line of props (what you have) will carry your boat but you gotta get them down in the water.

The lazer II is not a good choice for your outboard. I have yet to be able to make one do what I want.

Go with the simplest options first then work your way toward the more expensive.

Chris