3.0l merc turns 5000 rpms

[snake91876]

my 3.0l merc turns 5000 rpms and only gets about 30 mph, it has a 17pitch prop on it right now. it has a bolt on stingray fin and it is almost on plain immediately what prop do i need to put on it to keep it from reving so hard with no top speed or do you think i have coupler issues.

 

[jbh1024]

Re: 3.0l merc turns 5000 rpms

what size boat is it? i had an 18 ft stingray that was doing the same thing. when i got it , it had a 19 pitch prop but was reving to high and i had to go to a 21. if its a small boat i would up the prop a little then go from therer

 

[tommays]

Re: 3.0l merc turns 5000 rpms

It sounds in the about right for a 3.0 on and 18' boat

MOST boats like that come with a 21" pitch prop from the factory I have a 17" /19"/21" and 4 blade 20 "

I find the only time i would use the 17" Would be water sports or fully loaded with big people


And i have come to like the 4 blade 20" for general runnig around with 2 to 4 poeple on board

 

[snake91876]

Re: 3.0l merc turns 5000 rpms

it is an older 87' 18 imperial bowrider , i dont know if i should go with a 19 or a 20 i definitely want more speed but wont be really doing watersports maybe a tube behind the boat, should i leave that stingray fin on the outdrive , or does that slow it down

 

[Frankiea87]

Re: 3.0l merc turns 5000 rpms

hey i just picked up a 1987 18' imperial bowrider also... $800 bucks runs awesome and in good condition... got any pics of yours?

 

[Dandelion]

Re: 3.0l merc turns 5000 rpms

You need to go up in pitch.

Try a 14 x 19" pitch, 3 blade prop. That will increase your top speed, and bring your RPM's down to within the desired range at Wide Open Throttle. You will lose a little off the hole shot, but since it sounds like the boat is practically exploding onto plane with the 17" prop this shouldn't be an issue. My guess is that switching to a 14 x 19" prop you'll do about 34 MPH at 4600 RPM's, and the hole shot will still be quick because of that Stingray fin. The fin also allows you to stay on plane at slower speeds, and prevents the boat from porpoising. The smoother overall ride and better low end performance is well worth the 1 or 2 MPH you'd gain without the fin, IMO.