1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

[Racefan131]

Hi,

Just bought this boat needed new lower gear unit. Replaced all bellows, water impeller, thermostat, shift cable, all is good. Put it in water for first time ran great only problem could not get over 2600 RPM 1/2 tank of fuel 4 light passengers 25 MPH max. Throttle body is opening up full.
Question, is my propeller pitch way off. What are people with same size boat and engine running? Thanks

 

[craze1cars]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

I have no idea what a "27 DA" is....but it seems to me there's no reason that prop wouldn't get your RPMS considerably higher on most any planing boat, so I suspect you have a mechanical or electrical problem that is unrelated to the prop. But we really don't have enough information to go on. A few things to consider beyond what you mentioned:

What is your gear ratio?
What is your base timing set at compared to spec?
Have you tested your timing advance for proper operation?
Have you confirmed your tach is accurate?
Are all cylinders known to be firing?
Did you replace fuel filter and/or water separator?
Is your fuel known to be fresh and good?
Have you tested fuel pressure?
Is your flame arrestor clean?
Is it possible you have some clogged or malfunctioning injectors?
Was the boat planed out at 25 mph, or was it still plowing water?
Is your power trim working, and are you educated in how to use it properly?
Same for trim tabs, if equipped?
Have you checked for stored trouble codes in the computer?

 

[SparkieBoat]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

you could try a 17 pitch prop ..but you need 2000 more RPM at least. but maybe it will make a big difference, you should trouble shoot the motor first... it is also possible that you put the wrong gear ratio on the boat when you replaced the outdrive. thats my guess.

 

[Racefan131]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

Thanks for the reply. As I stated boat is new to me so I have a lot of things to learn. The first easy fix to my problem was to find out what pitch this boat came with Sea Ray shipped the Sundancer's out with a 24 pitch prop so I at least know that I am in the ball park. You have brought up a lot of questions that I need to find out. Going to start with fuel systems first. The funny thing is the engine runs great just no power, have to look into the gear ratio too. Thanks again.

 

[SparkieBoat]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

since you changed the outdrive..finding out the old gear ratio and the new gear ratio is first thing to do. if they are the same, then you have engine problems.

 

[Racefan131]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

Found out today Merc has 4 diffrent gear ratios. Mine is a 16:27, going to count rotations and see what I got.

Thanks

 

[45Auto]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

If you know the gearing you don't have to count rotations ......

27/16 = 1.69 to 1

Your gear ratio and prop pitch are where they should be, something else is wrong with your boat. Did you do a compression check on the engine? Is the throttle opening all the way?

 

[SparkieBoat]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

where did you get the 16:27 (1.69 : 1 )info from?? I assume that is the ratio you are supposed to have, and now you will test to see what gear ratio you currently have.

 

[Racefan131]

Re: 1999 27 DA 7.4 MPI Bravo 3 drive 22 pitch ss props

Found out today the lower gear unit that I put on is a 15:19 I need a 16:27 that is what the 2.00:1 calls for. Will have it re-geared in the winter. The engine is not the problem she is strong. Thanks for all your help.