120 performance probs

[jake3020]

Guys, I posted some problems that I'm having with planing and performance that some of you "experts" could probably add your 2cents too..

http://forums.iboats.com/showthread.php?p=2358785#post2358785

 

[hwsiii]

Re: 120 performance probs

Jake, please move the rest of your information to this forum.

Jake, I have already left a form for you to fill out, I must have lost my connection when I submitted the form.
I have no idea what boat you have, but from the picture it looks like a deck boat of some kind. The water was coming over the transom because the motor was mounted too low on the transom. What is the tach switch set to on the back of the unit. The arc could have shorted the tachometer out and that is why it is reading wrong. I show a Stiletto 31323 to be a 13 1/4 x 23 Advantage II prop, and I don't know your gear ratio, but I would say off hand that is too much pitch.
Please fill this form out and I will help you as much as I can.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing then do the same thing on the flywheel and turn the motor until the tape lines up with each other on the prop, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a digital tachometer and hour meter here: http://cgi.ebay.com/ebaymotors/Tacho...Q5fAccessories $ 35
RPM _________ Speed ______ GPS ______ No. of people ______ Gal. Gas ________
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way by just pushing the throttle at the helm and not at the carburetor, checked compression, and looked at the plugs and checked spark as well as timing and advance, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.



H

 

[Frank Acampora]

Re: 120 performance probs

Jake: if you have not done so already, go back to the Chrysler/Force forum and read my reply.

 

[jake3020]

Re: 120 performance probs

got it guys... i should have read this thread before the one on the force forumns. I will post all the information here...no need in going to the other force forumn. I'm very gratefull for the assistance.

ok, i still have to get the tach working, but this is what i have so far.

answer
1. 1997 suntracker PD21 deckboat
2. 20'-10" longe, 92" wide at widest point at hull/transom. Not sure what base weight is but all I can find is where it reads " 10 persons 1,400lbs" and below that "1,975lbs persons, motor"
2a. 150 HP
3. 2 adults, 2 children (or about 400 lbs), gas is about 20gal
4. currently just messing around, these problems are making me question what can I use it for??
5. Deep Vee?.i'm not sure how to do this, but I used a 2' edge and measured at the end of it (leveled edge) and measured 9"?so that is 9/24 or 4.5/12..is this enough to get close to the degrees? I'm sure you know around about what it should be or hopefully this is close enough for your calcs
6. 1997, force by mercury. 120 HP
7. 120HP. 2.07:1 gear ratio( per the motor manual..i assume you are talking about the lower unit here??)

8. max rpm per book, 4750-5250?.idle rpm 700-800
9. 1" exactly ( now that I moved it up). i no longer have water coming over the transom!!! although performance was not helped at all...and speed changed none at all.
10. not sure what you are asking for here?
11. no
12. stelletto M1323 is all I have to go off of.
13. my tack might be working?see below post about the setting in the back?if this works then I will take it back out this weekend.

14. 192m (630ft)
15. no to all of this
16. just bought the boat. This was the prop on it/
17. no
18. as noted in post above
19. just want it to plane out


frank, see below pic, this is what my tach looks like. it has these following settings.
2p, 4c
3p, 6c
4p, 8c
5p
6p
it is currently set at 2p, 4c (arrow is facing this set of numbers anyways)
so as you can see, i'm not sure which one of these is the #4 position as you noted...with one should it be set at? I do remember messing with this adjustment as i was looking for loose wires (before i found the short on the voltage regulator).


i was able to track the purple wire all the way back to the top cylinder in the engine...but this same wire runs to all the gauges on the dash...i quess this is normal...

 

[hwsiii]

Re: 120 performance probs

Jake look in your manual and it will tell you whether you need a 12 Pole or a 20 pole tachometer. It would help to know the RPM you are turning at WOT. You should be running about an 18"pitch prop with that setup on the boat instead of a 23" pitch and that is definitely part of the problem.
I don't know exactly what the circumstances are about this boat, but I can't imagine this boat was being used with that motor setup and that prop. It sounds like someone exchanged motors on this boat and just left the prop on it that was used for the boat it was on before. Because that 23"pitch is too much for this setup and you should be able to do over 35 MPH with this setup.


H

 

[jake3020]

Re: 120 performance probs

interesting..i have no history of the boat and setup as i bought it at a dealer that took it in as a trade-in. I will get the tach working this weekend and get back with you. thanks for all your input.

 

[Frank Acampora]

Re: 120 performance probs

The combination 12 and 20 pole tachs I have seen only have settings marked 1,2,3, and 4. Your tach appears to be standard Teleflex tach.

Now, cut me some slack on this, Jake, because I am dealing with a couple of assumptions and assuming makes an A** out of U and ME:

After 1991, Merc started changing Force engines radically so your 1997 MAY have a 12 pole alternator.

The tach is a 12 pole tach, looks like Teleflex from the back, but like women, they all look the same LOL. However, it appears that a grey wire is connected to the signal terminal of the tach. Grey is usually the color that Merc used for signal and since your engine is a 1997, it will have Merc ignition and wiring. Thus, I would expect the grey wire to be correct. It appears that the purple wire (you say it runs to all gauges) is a power wire, and of course, the black is ground.

NOW: if your alternator is 12 pole, that tach you have when used on an 8 pole Chrysler alternator would take a setting of 4P, so you can try setting the switch at 6P position. (do the simple math)

If you can get a good look under the flywheel, simply count the poles (knobs pointing toward the flywheel inside rim) with wire windings on them--there will either be 12 or 20.

 

[jake3020]

Re: 120 performance probs

frank, i believe you where right. i had to change the setting to 6p per this website. it seems to be working fine now.
http://www.mercurymarine.com/serviceandwarranty/outboardfaqs/electrical.php

 

[jake3020]

Re: 120 performance probs

looks like i posted this new information on the wrong thread again.

HWSIII,

alright i've got the tach working. and today the sun was shining and made for a good day to get the boat back on the water and run these tac test.
see below for a complete run down of your questions.
after this test it is clear to see that my WOT is below the manufacturers specs.

answer
1. 1997 suntracker PD21 deckboat
2. 20'-10" longe, 92" wide at widest point at hull/transom. Not sure what base weight is but all I can find is where it reads " 10 persons 1,400lbs" and below that "1,975lbs persons, motor"
2a. 150 HP
3. 2 adults, 2 children (or about 400 lbs), gas is about 20gal
4. currently just messing around, these problems are making me question what can I use it for??
5. Deep Vee?.i'm not sure how to do this, but I used a 2' edge and measured at the end of it (leveled edge) and measured 9"?so that is 9/24 or 4.5/12..is this enough to get close to the degrees? I'm sure you know around about what it should be or hopefully this is close enough for your calcs
6. 1997, force by mercury. 120 HP
7. 120HP. 2.07:1 gear ratio( per the motor manual..i assume you are talking about the lower unit here??)

8. max rpm per book, 4750-5250?.idle rpm 700-800
my current idle is at 1000 rpm
9. 1" exactly ( now that I moved it up)
10. not sure what you are asking for here?
11. no
12. stelletto M1323 is all I have to go off of.
13. WOT is 4,300 rpm....gps speed is 27.1mph

14. 192m (630ft)
15. no to all of this
16. just bought the boat. This was the prop on it/
17. no
18. as noted in post above
19. just want it to plane out. I went ahead and did the test here as you mentioned while i was testing it out. these are the results.
1500rpm-7.0mph
3,000rpm-20.8 mph
3,500rpm-23.6 mph
4,000 rpm-26.3 mph
4,300 rpm-27.1 mph WOT.

Hopefully this will give you enough information to help me out.
it is kinda sad to have this boat and not enjoy it. I took my son out with me tonight and he had to sit at my feet to keep from getting wet ( and i got soaked) becuase all i am doing is pushing the water instead of getting up ontop of it!!!

 

[steelespike]

Re: 120 performance probs

If youre pushing water :
Have you tried trimming the motor up/out? Sounds like like it is trimmed in too far
forcing the bow down.Boat must be planing at 27.So trimming out should raise the bow.If it doesn't you may have a hull problem or a severe setup problem.If you can get the bow up You'll get more rpm and speed.If the motor has a foil on it that could force the bow down.As hwsiii says you will still need to change the prop

 

[hwsiii]

Re: 120 performance probs

Jake, it appears that Frank got you fixed up with your tach, and it appears to me that Spike is right as always, that the motor is trimmed in too much as well.

Here are my numbers and the accompanying chart to go with them.

Prop Slip and Effective Prop Pitch

Prop Slip and Effective Prop Pitch chart

If you will notice that as you raise the RPM on your motor that your prop slip rises as well, and that is definitely NOT the way that prop slip works. As the RPM's rise Effective prop pitch should go UP yet it is going DOWN in this case, and prop slip should go DOWN and in this ase it is steadily rising. As a NORMAL course of events I would say that your prop is slipping on the hub in the prop.

BUT in this case my opinion is different because of your statements about all of the water coming from the bow of the boat. I looked at your Quote below this and it states that you appear to realize that for maximum performance of your boat that you need to trim the motor UP for maximum speed, and that is right.

1) when you are at WOT, with the motor trimmed for max performance, water comes pouring over the transom as if it is catching the front of the lower unit and funneling it up...I?m talking a major amount of water here!!! i think that the motor is sitting two low in the water and am questioning the need for a jack plate... I could only gain 3" by moving it in the factory provided holes ( it is currently set as low as possible).. What do you guys think? see attached pics for reference "motor mount 1" and "motor mount 2". there is no way that this water coming in like this can be normal. Through all the research I?ve done, I?m thinking that the anti- ventilation plate can be as high as 1? above the bottom of the hull ( that is about 5? higher than currently mounted). The current mounting holes will only allow the motor to be raised 3?.

3) When i am running at WOT, 26mph, I?m getting alot of spray from the front of the boat. it makes me think that if i was going a bit faster, and the boat was running higher in the water, then i would be above all of that.....The hole shot is OK, if you get on the trim immediately. This spray is very, very bad...All of my testing has been done with my wife and two small children. This will be the usual load. i also attached an overall pic of the boat so that way you can get a feel for what it's all pushing. I wish i could tell you what the weight was, but i cannot find that info.

So, reading the above Quote my opinion is you may either have a problem with the bottom of the boat at the stern, that could have been caused by being on the trailer wrong or chocked up wrong and it created a depression in the stern, and that would cause the bow to go down the faster you go, but this would be very unusual. Or you have water in the hull at the bow causing the bow to NOT rise at it should.


But I believe the REAL problem is you have a Power Trim unit that leaks down as you apply more power to the motor and thus the drive unit goes under the boat more and pushes the BOW down, thus stopping you from reaching your maximum RPM and speed. While you are running the boat at WOT you need to look back and make sure the motor is rising as you trim it UP and that you are able to make the prop start ventilating, by trimming the motor up, to prove the trim is working right and if the bow of the boat comes up and stays up it is working right. If you can not make this happen, then I am right in my hypothesis.

If this is not the problem, then I need more information, and you have a prop that the hub is slipping on and you need to borrow a prop of about 19" pitch and get me some new numbers like you did already.

I forgot to answer the question on the steering cable, that is NOT my forte, but it looks to me like it is wayy too tight a radius, and that was probably exacerbated by raising the motor up on the transom. If you cut a new slotted cable outlet to the starboard about 1' more I believe you will relieve the strain on the able and make the steering much easier. BUT there are people here who are much better at the cable angle than me, and if they say something different I would probably listen to them.



H

 

[jake3020]

Re: 120 performance probs

thanks for all this information.
i would say that it must be the prop slipping on the hub.
i had my son (40lb) sit on the motor and trim worked fine in driveway, but also it works great while running in the water with the ability to trim up and down easily and of course trim up until the prop starts cavitating. All readings where taken just below that point for maximum speed.
i'm not seeing any issues with the hull. everything is straight and smooth.

can i take the current prop to a prop shop and have them put a new hub in?

of course i know of know one with a 19" prop that would fit this set up, so i will have to buy one. OUCH!! of course from all the post that i've read. i need to have my RPM close to that 5250 and using 400rpm per inch in pitch drop, this 19" prop should get me close.....the joys of boat ownership.

i'm going to decarbon and change the plugs this weekend. I should be able to check compression as well.

I will post the results and changes after doing all of this thanks.

 

[hwsiii]

Re: 120 performance probs

jake, it is very easy to take the prop off and mark it with a permanent marker across the metal of the prop and the rubber hub then run it again, if the marks are NOT lined up then you KNOW the hub is slipping, and you don't have to guess.

But the prop slipping does NOT explain the bow throwing water everywhere.

i need to have my RPM close to that 5250 and using 400rpm per inch in pitch drop, this 19" prop should get me close.....the joys of boat ownership.

It is closer to 200 RPM per inch NOT 400. And yes a prop shop can do it.



H