3.0 merCruiser Max out at 4000 RPM.

[SurfsideStingray]

I just purchased a 2006 stingray 185 LX open bow Boat with a 3.0 L MerCruiser and alpha one drive. I took it out for the first time and I noticed the WOT at 4000rpm and 40mph. It has a really nice stainless steel ballistic prop that is 14 3/8×21 pitch but the propeller has a few dings and rolled edges from previous owner hitting the ramp. Looking to get a new prop and wondering if I should get a different pitch prop ? I believe this boat should be hitting around 4500 RPMs for that motor?

 

[Scott Danforth]

first, welcome aboard

second, I would send the stainless prop in to get repaired. you may be loosing RPM's because the ends are folded over, and repairing a prop is much much much cheaper than buying a prop.

 

[SurfsideStingray]

Yes I plan on getting it repaired but it takes several weeks to get shipped out and back I want to buy A cheaper aluminum one for now. From what I read it’s probably good to go to a 19 pitch

 

[Scott Danforth]

Yes I plan on getting it repaired but it takes several weeks to get shipped out and back I want to buy A cheaper aluminum one for now. From what I read it’s probably good to go to a 19 pitch

where do you live that you cant simply take it in and drop it off?

 

[QBhoy]

Hi. All being normal. You should be able to turn a 21” well. Very quick boats these. May even need a 23”. I’d also add that a ballistic prop is literally thee worst ever prop for using as a bench mark to compare other prop pitches. They behave so strangely and often inconsistent too. Trade mark of these is that they either work or they don’t. Nothing in between. And almost alway…when compared to another prop of same pitch…will be extremely noticeably slower to plane. Always. If you want a bench mark prop for starters..stick on a black max 21” or a good laser 2 21”. Take it from there. You always know where you are with these two. Consistent and reliable as you’ll ever get from a prop. Sorry to ask..but are you trimming up optimally when you are at 4000 rpm and 40 mph ? If you aren’t…you’d likely gain around 400 rpm at least by doing so. Ballistics rely on plenty trim and running on the surface

 

[Scott Danforth]

3.0's wont spin a prop above 21p just not enough motor there for the 1.98:1

so the 23p is not going to happen

the stingray 185x weighs 2200# which is a lot of boat for that little motor.

 

[QBhoy]

3.0's wont spin a prop above 21p just not enough motor there for the 1.98:1

so the 23p is not going to happen

the stingray 185x weighs 2200# which is a lot of boat for that little motor.

Scott. Wouldn’t be one to argue with a fella like yourself most days. But I’d say it defo would. Might not be great out the hole…but I’m sure it would be into the rpm range and good for into the 40’s. Of all the boats I’ve known with a 3.0 and around that size. Without doubt, this particular boat and an old 79 Glastron cvx16 ss with the early 140 3.0 are far and away the best result I’ve ever known from the 3.0 and a 23”. The stingray I’ve seen achieving nearly mid 40’s and the cvx at least the same but actually indicating a suggested 5000 rpm on the tachometer. I know of a maxum 1800 that could turn a 23” to just over 40 and in the rpm range. But wasn’t ideal all round and certainly not with a few on board. That was changed out for a 21” laser 2. Ran very well pitched with that. Around 40 and at the top of the rpms for sure. Honestly Scott. Some boats will manage it. Only doubt in my mind would be if they had a lower ratio…I presumed they were about the 2-1 ratio naturally. Not aware of a lower ratio on things like that. Might be wrong though.

 

[Scott Danforth]

check the tach, gm inliner motor wont spin above 5000 on its own