290 Sundancer - twin 190 hp 4.3 ltr mercrusier performance?

Herrickjde

Member
Jul 28, 2019
68
Jacksonville, FL
Boat Info
SeaRay 290 Sundancer 1998
Engines
2 Mercruiser 5.7 350 EFI 310 HP - Drive - Alpha 1 / Gen 2
I have a 1998 290 with twin 4.3 mercrusiers as well. How fast does your boat run and at what RPM's ? I have stainless steel 4 blade props with 17 pitch on the boat now and it runs 24 to 25 mph at 4,000. That is it ? I tried a set of stainless steel 3 blade props with 15 pitch (came with the boat) and the 4 blade was much better and not difference in top end. I have been told that since my outdrives were replaced by the previous owner the gear ratio may have been changed on the Alpha 1 gen 2 drives as there are 4 different gear ratios available. I am trying to figure out what is normal for this boat with these engines. It is a bit hard to plane with 4 or 5 people on board. They need to move to the front until we plane. Yes I have the drives and trim tabs all the way down
gear ratios.jpg
 
I have a 98 290 with twin 5.0 and alpha 1 gen 2 drives. I run the 3 blade ss props. At 4000 rpm i am turning 30 mph
 
You should be able to get the engines well into the upper 4,000 range. A couple things can cause low RPM. Just off the top of my head: improper trimming of the drives, a dirty hull bottom/running gear (or damaged), too much weight on the boat, bad fuel quality, old/failing engine parts like cap/rotor/plugs/wires, throttle cable issues or a sick/tired/old engine.

There's a serial number on the side of the drive. Or, what about paperwork from the previous owner? You go to SR's website and under the owner's resources area there is a prop matrix. It will show original drive ratio and prop.

If anything, the original props would be a higher pitch... which in your present condition, would cause the RPM's to be even lower. It's not healthy for the engine as it is right now, fyi.
 
You should be able to get the engines well into the upper 4,000 range. A couple things can cause low RPM. Just off the top of my head: improper trimming of the drives, a dirty hull bottom/running gear (or damaged), too much weight on the boat, bad fuel quality, old/failing engine parts like cap/rotor/plugs/wires, throttle cable issues or a sick/tired/old engine.

Thank you for the response; I have also been told what you have said above. I bought the boat in July 2019 and it was surveyed and I was told the fuel may be the problem and replaced all the fuel filters and it did a little better. The bottom was done in April 2019 and kept on a lift until I purchased it. It has been in the water since, but out a few times and we pressure washed the bottom and it looked fine. I am waiting on paperwork for some major work done. both outdrives were replaced with SIC rebuilt drives (don't know the gear ratio yet). Port engine is totally rebuilt and Starboard was worked on. The weight is suspect as it is just me and 3 adults. PS: drives and trims are working correctly.


There's a serial number on the side of the drive. Or, what about paperwork from the previous owner? You go to SR's website and under the owner's resources area there is a prop matrix. It will show original drive ratio and prop.

I went to the searay site and owners section, but they only offer 2008,9,&10 and I need 1998. I also went to the mercruiser site and based on the 3 different gear ratios my props are different. With gear ratio 1.62 the pitch should be 4 blade 15 and I am running 17. Gear ratio 1.81 pitch should be 17 and I am running 17.

If anything, the original props would be a higher pitch... which in your present condition, would cause the RPM's to be even lower. It's not healthy for the engine as it is right now, fyi.
 
Their website has been wonky. There should be, obviously, a whole lot more years to pick from! The Sea Ray Owner's Club website has more info. According to that (which is the same prop matrix as what should be on SR's website), you would have had 1.81 gears and 13.75x21 Vengeance props (those are SS props).

Even with the weight you stated you are running in your boat, you shouldn't be having these issues.

There's definitely something amiss. Regardless of what drive ratio you have, if we assume that everything is "healthy", then you would need to drop down to something like a 13" pitch prop to get your proper RPMs - which obviously isn't correct.
 
Their website has been wonky. There should be, obviously, a whole lot more years to pick from! The Sea Ray Owner's Club website has more info. According to that (which is the same prop matrix as what should be on SR's website), you would have had 1.81 gears and 13.75x21 Vengeance props (those are SS props).

Thanks and on the boat now is Mercury 48-825901A46 Offshore Series 14 Inch X 19 Pitch 4 Blade SS Props. I assume that the 21" above is a 3 blade prop and a bit larger than the 19". I also have a spare pair of VENGEANCE (14 X 19")
PROPS 48-16316A46 3 Blade props that came with the boat. As I mentioned I switched the props and non top end difference. As I mentioned I am waiting on paperwork from a vendor to tell me the serial numbers of the rebuilt SIC outdrives currently install a few months ago.


Even with the weight you stated you are running in your boat, you shouldn't be having these issues.

There's definitely something amiss. Regardless of what drive ratio you have, if we assume that everything is "healthy", then you would need to drop down to something like a 13" pitch prop to get your proper RPMs - which obviously isn't correct.

My engines are running great and one was rebuilt and the other had major work. Based on yours and others feedback it may be a drive ratio / prop thing.
 

Forum statistics

Threads
112,948
Messages
1,422,808
Members
60,930
Latest member
Ebrown69
Back
Top