1988 Bayliner 2556 5.7 OMC Cobra-gctid395403

[Guest]

I know there's alot of you guys out there that own or have owned this boat. I'm trying to get a consensus on the propeller that worked best for this particular application. I've tried several different ones and have not really found one I'm happy with. I love the boat and know the performance with this package is not for speed.

[Guest]

Wish I could help, but welcome.

I just found out the other day that the WOT is on top of the fire suppressor or Air cleaner as I would call it. I have mine proped right as I hit wot, get out of the hole. I think that is what you go buy. Somewhere on there is a sizing chart.

[Guest]

gto64dr wrote:
I know there's alot of you guys out there that own or have owned this boat. I'm trying to get a consensus on the propeller that worked best for this particular application. I've tried several different ones and have not really found one I'm happy with. I love the boat and know the performance with this package is not for speed.

151/2 x15 is stock.

[chris]

Im using a 15 1/2x 14 ss, and at 3500rpm im getting 25mph, and a WOT of 4200 ..top speed 31mph depending on weight of course, I swaped to an aluminum 15 1/2X 15 and was getting 3400rpm at 21mph didnt check WOT

[Guest]

Well I ordered an OMC original 15 x 15 SST prop. Once I get it and install it I'll post my results for anyone interested.

[Guest]

So I got my new prop. 15 X 15 OMC SST, set my timing to 30 BTDC @ 3500rpm, cleaned my spark arrester and went for a ride. All trimmed out for max speed, I was able to get 20mph(GPS) at 3600rpm. Sounds good, right? Problem is that was at WOT and wouldn't do any more. Cruises at 17mph @ 3200rpm. Anybody have and idea why I can't get more rpm or speed.

[Guest]

gto64dr wrote:
I know there's alot of you guys out there that own or have owned this boat. I'm trying to get a consensus on the propeller that worked best for this particular application. I've tried several different ones and have not really found one I'm happy with. I love the boat and know the performance with this package is not for speed.

The 7.4 was a 40 mph bomb!!! Wow what a fun boat.:worth

[Guest]

gto64dr wrote:
So I got my new prop. 15 X 15 OMC SST, set my timing to 30 BTDC @ 3500rpm, cleaned my spark arrester and went for a ride. All trimmed out for max speed, I was able to get 20mph(GPS) at 3600rpm. Sounds good, right? Problem is that was at WOT and wouldn't do any more. Cruises at 17mph @ 3200rpm. Anybody have and idea why I can't get more rpm or speed.

If you were able to go faster and hit higher rpm's before the new prop, I would say you now have too much prop. Engine doesn't have the power to turn it any faster.

[2850Bounty]

green650 wrote:
If you were able to go faster and hit higher rpm's before the new prop, I would say you now have too much prop. Engine doesn't have the power to turn it any faster.

Fully agree!

Before you can actually test different props and do a WOT RPM check, the hull must be clean, engine in full tune ..... and this means everything; fuel delivery system, etc. etc. and ignition TA as per OEM specs.

The test is futile without this having been done.

.

[Guest]

The engine is in perfect tune, new plugs and wires, timing set at 30btdc at 3500rpm. Starts right up and runs smooth, no hesitation, runs right at 175(closed cooling system). Stands up and goes, gets on plane by 15mph regardless of the prop (12 x 24 trim tabs). Just doesn't want to crack the 20 -21mph barrier.

I'm not sure that a 15" pitch prop is correct despite what everyone says and the prop company's say. Does anyone know exactly what size props came on this boat? Because with the test results I am getting it seems like 15" pitch is 2" too much pitch.

If there is nothing else wrong wouldn't a 13" x 3 blade increase rpm's by about 400, therefore putting me in the area of correct rpm's.

[2850Bounty]

gto64dr wrote:

• 1 wrote:
• The engine is in perfect tune, new plugs and wires, timing set at 30btdc at 3500rpm. Starts right up and runs smooth, no hesitation, runs right at 175(closed cooling system). Stands up and goes, gets on plane by 15mph regardless of the prop (12 x 24 trim tabs).
• Just doesn't want to crack the 20 -21mph barrier.
• I'm not sure that a 15" pitch prop is correct despite what everyone says and the prop company's say. Does anyone know exactly what size props came on this boat? Because with the test results I am getting it seems like 15" pitch is 2" too much pitch.
• If there is nothing else wrong wouldn't a 13" x 3 blade increase rpm's by about 400, therefore putting me in the area of correct rpm's.

• 1 wrote:
• Excellent! That's the first hurdle to overcome.
• About all you can do is just keep trying propellers that keep the engine within the WOT RPM range.
  
  FYI: WOT RPM is a test RPM only.... not an RPM to be sustained.
• See above #2!
• The Cobra prop diameter limitation is an issue as it is. I don't think that reducing diameter is going to help you.
  
  See above #2 again.

Just so you know, your OMC Cobra drive is a candidate for the DP-S conversion.

.

[Guest]

I have a 15x11 inch pitch and it does great lower pitch higher rpm boat will do 23 knots top speed this is a big heavy boat thats about all she has with a 260 hp 5.7 merc

[Guest]

23 knots? Thats 27 mph, I would give my left one to hit that!

[2850Bounty]

gto64dr wrote:
23 knots? Thats 27 mph, [SIZE]4 wrote:
I would give my left one to hit that![/SIZE]

Give one of us your credit card authorization number and shipping address...... and we'll have you hitting that, and more, in short order! :kidding

[Guest]

2850 bounty where can I find one of those out drives you posted and what is the cost. I also have a cobra and would love to do a conversion on mine to the dp-s

I found a company online but can't get them to contact me back.

I have the same boat and i am running a 15x15 aluminum on mine I have no promises getting on step fully loaded and no matter how much weight I have in it I cruise at 23kts at 3600 rpm's and i can get 4200 at wot I would like to try a ss prop to see if it would do any better.