Speed & RPM's - 1998 SeaRay 290 twin 4.3 Mercruiser 190hp

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 was curious if any of you have this boat with the 4.3 190 HP Mercruiser engines and what is your cruising speed mph and RPM's and top speed mph and RPM's. I have a hard time getting mine to plane and then once planed only get about 25 mph 3900 to maybe 4000. I have a 4 blade prop that came with the boat, but the previous owner gave me a pair of 3 prop blades stainless and I wonder if I change the props would it go faster? Also, I am having the benton trim tabs checked and outdrives to make sure they are going down all the way. Thanks,
outdrives.JPG
 
I'd put the 3 blades on as a test -- are they the Mercury Vengeance 19p? I think those were stock. Just to see how it runs. You should turn up to 4400-4800 on the 4.3L's

Does the 4 blade have a pitch or model on it? It might just be too much prop
 
Bottom clean? Props and drives clean? Number of pass onboard? 4K rpm is a low WOT. Sounds like slippage, overpropped, or dirty. Usually the 4 blades have more bite and time to plane improves. If both motors are same rpm at WOT then seems like prop or bottom. Unlikely both drives and tabs have same issue of not going through full ROM. You would have likely noticed significant listing if only one side was affected.
 
I wanted to give you guys an update. I pulled the boat out and the bottom is clean. We put the 3 blade props on and not good performance and put the 4 blade props back on and it ran about 3900 to 4000 25 mph. Thanks
 
I wanted to give you guys an update. I pulled the boat out and the bottom is clean. We put the 3 blade props on and not good performance and put the 4 blade props back on and it ran about 3900 to 4000 25 mph. Thanks
Sorry but that’s still not right, you’re overpropped, overloaded, or have a drivetrain issue. You need to turn up to 4400 minimum.
 
Thanks for the feedback. Since I recently purchased the boat I know the outdrive lower units were replace less than 6 months ago (SEI Marine rebuilts Orlando, FL). The props are 4 blade stainless 17 pitch the 3's are 19 pitch and didn't perform well. Once I mess with the trim & trailer switches and get the drives down I can plain, but still no more than 4,000 rpms. Where should I start the troubleshooting process to minimize investment. What I know is the engines are running good and unless they put the wrong drives on the boat (gear ratio). It was just me and 3 other people on the boat. Thanks
 
It should turn in the 4400-4800 range with either one of those propellers. Since the drives were recently replace, I would verify the right ratio was put on - should be a 1:81 on a V6. If all that checks out I would start looking at things common to both engines like fuel restrictions.

Granted it's a smaller boat, but my 4.3/Alpha I with a 1:81 ratio will turn 4900 with a 21p 3 blade aluminum and 4600 with a 23p 3 blade aluminum.
 
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