Bayiner won't Plane out

[sturgis]

I've restored a 1985 Bayliner Ciera 2755 with AQ260 (350 Chevy) and 280 out drive. I replaced the Prop with a 15"x19, 3 blade Aluminum as the specification called for. The WOT is 2200 and speed according to the Lowrance is 12 at best. If I back the thorotle of to 1700 the speed stays the same. The engine has a new electronic ignition, new plug, rebuilt Carb, timing is 10 BTC and advance works, It runs smooth. I am convinced that I have way to much Pitch for this boat, its loaded (approx 6500 lb). I am considering prop options and thinking 15"x 15 pitch, I am hoping for 25 to 27 MPH at 3600 RPM with 4400 t0 4500 RPM @ WOT, can someone tell me if I am on the right track.

 

[ufm82]

Re: Bayiner won't Plane out

2200 seems like half of what the WOT should be. Isn't a 5.7 rated to run at 4500-4800 rpm? I would be looking at why you are only getting that kind of RPm out if the engine. You say it runs smoothly but you aren't getting full rpm. Does the throttle plate open fully when the throttle is advanced all the way? The low speed makes me think it's a true lack of rpm issue more than a faulty tach. 2200 is barely twice idle rpm.

UFM82

 

[sturgis]

Re: Bayiner won't Plane out

Over "three" time idle speed. The tach is fine, idles at 700 and will peg in neutral.

 

[craze1cars]

Re: Bayiner won't Plane out

Based on conventional theory, if you are at 2200 top RPM now, and you drop 4" of pitch from a 19 to a 15, your new RPM will soar all the way up to 3000.

Which is still way too low for that motor.

But that's a huge and heavy boat for a single 5.7L. What is your outdrive's gear ratio? If you are 100% convinced your motor is now running at its peak, then I believe your outdrive is geared far too steep for this application and you must gear it down to compensate for the load.

I don't think there is a prop on the market that will have low enough pitch to bring your RPMS up to the 4,500-ish you want and need.

Your problem is in one of two places that are not prop related: 1. Motor not set up and/or not running correctly 2. Wrong gear ratio.

 

[45Auto]

Re: Bayiner won't Plane out

I replaced the Prop with a 15"x19, 3 blade Aluminum as the specification called for. ..... I am convinced that I have way to much Pitch for this boat,

What ratio is your outdrive?

This 27' Bayliner (5800 lb dry weight, it would be right around 6500 wet) with a 250HP 350 motor and a 1.62 Alpha outdrive uses a 17" pitch prop. It cruises at 26 MPH at 3500 RPM, so I think your expectations are realistic.

http://www.boattest.com/boats/boat_video.aspx?ID=902#bt-Overviews

If your outdrive is around 1.50 (10% lower ratio), then you will most likely need a prop about 10% lower in pitch then 17" they used, which would put you right at 15".

If you ever get the thing on plane it will let it rev higher. Right now you've pretty much discovered displacement speed for your hull, which is why it doesn't make any difference in speed between 1700 and 2200 RPM. It can't climb out of the hole it's creating in the water to get on plane. You need a little extra push to get it over the "hump" and onto plane.

I would do a compression check and verify that the engine is healthy before spending money on a prop, but it is entirely possible that a slightly lower pitched prop would let it get on plane, at which time it'll make a HUGE difference in RPM. The generic prop rule of 200 RPM / inch of pitch doesn't apply when one prop will not let it plane but the other one will.

Do you have trim tabs on your boat? I've driven a Sea Ray 260 with a 300HP 350 and a Bravo 3 dual prop drive at about the same weight as your boat. It was a real dog coming onto plane, I don't believe it would have made it if the trim tabs didn't work. You've got a lot of boat for a 350.

 

[boat1010]

Re: Bayiner won't Plane out

I agree with craze1cars. Look at the gears. I have a 24' and with a 454 with a few people in it getting it up on plane. Thats a lot of work for a 350. Is this a "new to you" boat? Has it always been like this?

 

[craze1cars]

Re: Bayiner won't Plane out

What ratio is your outdrive?

The generic prop rule of 200 RPM / inch of pitch doesn't apply when one prop will not let it plane but the other one will.

Very true. I did not think to consider this when I wrote my response. Thanks for the reminder. Get it up on top of the water and indeed resistance drops down dramatically...and RPMS will therefore go up dramatically as well.

 

[dazk14]

Re: Bayiner won't Plane out

Very true. I did not think to consider this when I wrote my response. Thanks for the reminder. Get it up on top of the water and indeed resistance drops down dramatically...and RPMS will therefore go up dramatically as well.

You'll also be getting into the RPM range where the motor makes far more power. The 150/200 RPM's per pitch works fairly well when nibbling close to max HP RPM.

 

[steelespike]

Re: Bayiner won't Plane out

He's running a 6500 lb boat seems to me a 19" pitch is too much.And a 15 pretty close.

 

[sturgis]

Re: Bayiner won't Plane out

I have done a compression check, the lowest Cylinder was 95lb the rest around 110lbs. The butterflies open full and it stains harder. Im 63 years old and Ive been rebuilding and setting up engines since I was 16. I've rechecked and im convinced that it's not the engine. That would have been to easy. I do have power trim tabs and have played with them, they help a little. As far as the gear ratio, four gear sets are listed for the AQ280 1.68,1.78,1.95,2.3 to 1. I can see where there would be a lot of difference from 1.68 to 2.3. My slip is at Tablerock Lake bout an hour and a half away so I will not be able to check the name plate till the weekend. I have had the boat and been restoring it for two years. As far as I know this is the original outdrive with factory gears. As I said I did change the prop. By the way I ran the calculations and a 19 pitch at 4400 RPM calculates to 41 MPH at 100% efficiency, we all know that ain't happening.

 

[45Auto]

Re: Bayiner won't Plane out

I have done a compression check, the lowest Cylinder was 95lb the rest around 110lbs.

Volvo specs from the factory service manual are 142 - 156 PSI at cranking speeds for an AQ260. You're down about 25% in power on your best cylinders, and about 33% on the low one. Could make getting the performance you're hoping for kind of difficult.

Good luck!

 

[sturgis]

Re: Bayiner won't Plane out

Volvo specs from the factory service manual are 142 - 156 PSI at cranking speeds for an AQ260. You're down about 25% in power on your best cylinders, and about 33% on the low one. Could make getting the performance you're hoping for kind of difficult.

Good luck!

I checked my records and found Cyl 1=120, 2=110, 3= 110, 4=95, 5=110, 6= 95, 7=130, 8=150. This was done just after I got it, the Boat had sit for a long period. Now that Ive run it a few time I probably need to warm it up and recheck. Never say never or It can't be that! I have assumed this to be the factory set up but it occurs to me that it could have been changed out with one that has gears for a 454 or a two engine set up.

I have received some very insightful information. I have not ruled anything out and will follow up on each point. I have found the prop that I took off It is marked Michigan 082073 1, 25 97, Can anyone tell me what it is. If my measurements are correct it is a 15'' and pitch measures 14? or 16? Im sure everone is better at measuring than I am.

 

[sstocker31]

Re: Bayiner won't Plane out

Can you just put the old prop back on and try it, or is the prop too far gone?

 

[sturgis]

Re: Bayiner won't Plane out

Yes I believe I can. I remeasured according to instructions on this site (www.propellerpages.com/?c=articles&f...pitch_measurement) The Prop is a 15' x 17p. it was dinged on one blade, bent the leading edge and knocked the cup out. I have recontoured and dressed it as close as possible and think I can run it with very minimal vibration. If It will plane out this will give me very good data to determine where to go from here. I will follow up once I have done a test run. Thanks! Bob

 

[sturgis]

Re: Bayiner won't Plane out

Got to my boat 10:00 PM Saturday night, found my 3 ft stern light laying on the deck with an empty jar of peanut butter. Had left the sliding glass to rear birth open by accident. Everybody knows what comes next. Raccoons got in and ransacked the galley, Crackers, assorted Chips and of course peanut butter. Nothing torn up just a 2 hour clean up. By the way the stern light was used to scrape out the peanut butter, I'd love to have a vidio of that. Sunday I changed the prop and prepared for a test run. I got half way out of the slip when the shifter stopped working. About two and a half hours latter I had the bad shifter cable out laying on the deck. Test was postponed till a latter date, Cable is on it's way. By the way temperature was 105 degrees above deck.

 

[craze1cars]

Re: Bayiner won't Plane out

LOL.

Sounds like a fantastic day of boating...

And people wonder why we love this sport so much...

 

[sturgis]

Re: Bayiner won't Plane out

I installed the new shift cable, little tricky with the outdrive under water. When I ran with the 15 X 17P the RPMs went to 3300 RPM and speed was 22 MPH, when I backed of I could go to about 3000 RPM and stay around 20 MPH, One big improvement was the steering, I had adjusted the skeg radically to the left to compensate for it pulling left and it was still pulling left. With the 17P it was pulling slightly right. I went back toward center half the distance and it held course. Earlier I moved the trim rod on the outdrive one hole to the closest in hole to try and correct steering I may need to back it up at least where it was. The 19P to 17P changed RPMS by 1200 (19P = 2200RPM at 12 MPH), if that holds I"ll get to 4500 RPM with a 15P, however it would seem that as I get closer the RPM change will be less radical. I would like to go to a stainless prop to get every bit possible from the prop but at three times the cost I don't want to commit till I am certain. Any thougths anyone?

 

[craze1cars]

Re: Bayiner won't Plane out

Sorry to answer your question with another question...but...whatever happened with the low compression readings? Has the engine been fixed? I would not recommend spending $300 to $400 to put a stainless prop on a boat with a sick motor....save the money and put it toward a rebuild....it still seems you are down on horsepower.

You are correct in assuming that you will not get such a drastic change in RPMS anymore with a pitch drop. This is because you are now getting the boat on plane and not running like a displacement hull. So if you go down from a 17 to a 15, I suspect a much more conventional change of probably +300 to 400 rpm. So expect probably 3,700 max if you buy a 15, and maybe just a little bit more speed than you had before...but not much if any.

If you get your compression back, and get the motor running strong as new, your HP (and therefore your RPMS) may go up substantially, and you'll have to reprop again.

 

[sturgis]

Re: Bayiner won't Plane out

Good point. I never did recheck the compression but will. I'm thinking another $100.00 for a 15P and look at a rebuild this winter or next. If I can get another 300 to 400 RPM and 3 to 4 MPH I'll be pretty happy for now. I use this boat as a live aboard, It's pretty nice, air conditioned, TV/DVD, gas grill, queen size bed, toilet w/shower. I also have what I call a "water taxi" 15' tri hull/ 85hp Evinrude great and inexpensive for fishing coves and running here and there. I do want to get it (Bayliner) running tip top though. I'll let you know how the 15P does.

 

[sturgis]

Re: Bayiner won't Plane out

I rechecked the compression and found that I still had a problem, however not as bad as the original readings. Cyl 1="120", 2=145, 3=150, 4=150, 5=145, 6="120", 7=160, 8=155. You will recal that with the 15"x19, 3 blade the WOT was 2200 RPM and speed according to the Lowrance was 12 at best, at 1700 RPM the speed stayed the same. With the 15''X17P it increased the RPMS to 3300 RPM at about 22 MPH. Since then I had major engine trouble (always insure that the "O" ring stays on the old filter not the engine!). I now have a 350 chevy /300 HP upgrade. With the healthy engine and a 15"X 15p 4 blade prop I am now getting 4000 RPMs and 24+ MPH. I can back it off to 3600 (half throttle) and it still gets 21 to 22 1/2 mph. So much for the 200 RPMs per pitch rule. It does not apply to this weight, at least not with the size engine I have. I have not done anything to the carburetor jets to compensate for the increase in HP. I intend to go up 1 size. With 6 Hours on the engine the plugs are a little gray with brownish tint. Also does anyone have a recomendation on how to set the secondary butterfly on a Rochester Quadrajet? Should it be open with no vacuum and if so how much. Any Carburetor wisdom is appreciated, especially if you know a good tech site for this carb. One last note, I still have not found the gear ratio, that may be a place to get the other 500 RPM in the future. Even though Im not geting the 4500 RPM it is plaining out fairly quickly, runs steady and losses only about 1 mph on turns.