3.0 mercruiser top speed??

[Rpo_2002]

I'm not sure if I'm even posting this in the right category. But I just purchased a 1993 Wellcraft 182s w/3.0 mercruiser. I don't know much about boats. I was wondering what top speed shud be?? We took it out for the time today and it took for ever to plane out then it top speed at 5000 rpm at 29 mph. So no low end and not much high end. Is that what I shud expect from a 3.0? Or is there something I can check on it with out spending on it already.

 

[H20Rat]

Re: 3.0 mercruiser top speed??

compression test maybe? Just because it is hitting a decent rpm doesn't mean its a healthy engine. Just means someone might have propped it down to make up for a sick engine that isn't running on all cylinders.

 

[jesus94p]

Re: 3.0 mercruiser top speed??

Sounds like an under propped engine. Might not want to keep running it like that since you might be over reving the engine.

 

[Dave.Mishchenko]

Re: 3.0 mercruiser top speed??

The max RPM for WOT on the engine is 4400 - 4800 so you don't want to run it at 5000. Checking the prop and compression is a good place to start. If you look at the sticky posts in the Prop forum you'll find some info you should collect if you have further questions about the prop and there's a forum for Mercruiser engines if you have further questions about that.

 

[Bayliner175xt]

Re: 3.0 mercruiser top speed??

Hi, we have a Bayliner 175 Bowrider with a 3.0L Mercruiser.
I would check your compession, it should be around 185PSI per cylinder. We hit about 42mph in our boat and it plains within 1-2 seconds. our prop is a 13"-22P 4 blade and we also run SX Samrt Tabs.
Your WOT RPM is 4400-4800 RPM..... not 5000.

We have no trouble pulling out a slalom skier.or even 3 single tubes, so i would be checking engine out.
Hope you find the problem, let us know what you find.

 

[YankeeDiver]

Re: 3.0 mercruiser top speed??

I have a 95 MAXUM 17 foot with the 3.0 engine. I just bought it a few weeks ago so I am still messin with the trim to get the most speed out of it. In my tests I am averaging WOT of 4500-4600 at 42 MPH. This is with three adults in the boat.

 

[Philster]

Re: 3.0 mercruiser top speed??

29 mph is way off? If she hits 5000 RPM that is good news w/out knowing real information like compression, etc. Still, it could be erased quickly if the prop is so small even a weak engine will spin it up.

You could be more than one size too small on the prop. Although, jumping up in prop size won't exactly add 12+ MPH to the boat.

You definitely need a clean bill of health for the engine before doing anything.

There is a chance, just a chance, that it has a tiny prop AND you aren't trimming up the outdrive when on plane or top speed run.

First: Are you trimming up the drive? If not, she probably has more revs and a way too small prop!!! If you are hitting 5000 rpms, AND NOT trimming up the drive for a full throttle run.... all your problems might be solved by going up two steps in prop size AND trimming that drive up!

 

[45Auto]

Re: 3.0 mercruiser top speed??

If you're comparing speeds, make sure everyone is using a GPS. Standard boat (pressure) speedometers are useless below about 20 MPH, and tend to read too fast by several MPH once they start working. I don't think I've ever seen one that read too slow, unless it was plugged and not working at all!

The standard 1992 3.0L (115HP) should be propped to run between 4200-4600 RPM. If it's a 3.0 LX (135HP) it should be propped to run between 4400-4800 RPM. Download factory manual #13 for all the specs on your engine from here:

http://forums.iboats.com/showthread.php?p=1693398#post 1693398

If you have your boat trimmed correctly, then 29 MPH is a little slow. Do a compression test to make sure the engine is OK, then a complete tune up (plugs, wires, cap, rotor) if one hasn't been done lately. Borrow a prop with 2" to 4" more pitch than your current prop to see if it gets you into the mid-4000 RPM range. Your speed should hopefully come up to around 40 MPH.

 

[maharg]

Re: 3.0 mercruiser top speed??

I only get 30 out of mine running with 4-5 people and gear/cooler/fuel. If I am empty I get another 5mph or so. I have a 17p prop and a 16.5 ft boat with good compression.

 

[ezmobee]

Re: 3.0 mercruiser top speed??

I only get 30 out of mine running with 4-5 people and gear/cooler/fuel. If I am empty I get another 5mph or so. I have a 17p prop and a 16.5 ft boat with good compression.

I would really think you'd be able to see 40MPH with a light load. Wet foam maybe?

 

[maharg]

Re: 3.0 mercruiser top speed??

No, its dry, floors were just redone last year and new foam installed.

 

[45Auto]

Re: 3.0 mercruiser top speed??

Since Maharg is admitting the truth about his boat, I guess I can post about my 16' 1982 Mark Twain with a 120HP 2.5L (precursor to the 130HP 3.0L) that will do 34 MPH (GPS) at WOT with only me on board.

I'm usually hesitant to post about it because it seems to provoke the ire of some 4 cylinder owners who will immediatly be posting that theirs will pull up four or five 300 pound skiers at once while running 60 MPH, delivering better gas mileage than a sailboat, and getting more valuable every day!

 

[oldjeep]

Re: 3.0 mercruiser top speed??

I've never checked mine with GPS, but I havn't seen anything faster than 38ish mph on my 19ft bayliner 195, which tops out at 4200 RPM. (14.25 x21 prop)

Usually have 5 people (650 lbs) in the boat.

 

[maharg]

Re: 3.0 mercruiser top speed??

I should put that my Wot with just me is 4600, and with everyone aboard is 4200

 

[Rpo_2002]

Re: 3.0 mercruiser top speed??

Thank everyone for there comments. I was using a gps and 29 mph was it. No gear just 3 people. My prop size is 15.25x15. I will have someone check my compression.

I do have the 135hp 3.0

 

[oldjeep]

Re: 3.0 mercruiser top speed??

I've never checked mine with GPS, but I havn't seen anything faster than 38ish mph on my 19ft bayliner 195, which tops out at 4200 RPM. (14.25 x21 prop)

Usually have 5 people (650 lbs) in the boat.

I did check with a GPS a few days ago and the speedo is a tad off. Top speed via GPS was 43 MPH

 

[oldjeep]

Re: 3.0 mercruiser top speed??

Thank everyone for there comments. I was using a gps and 29 mph was it. No gear just 3 people. My prop size is 15.25x15. I will have someone check my compression.

I do have the 135hp 3.0

15.25x15 sounds way off for a 3.0L in an 18 ft boat.

You should be closer to a 14.25 x21 prop for your setup

 

[rs1lollie]

Re: 3.0 mercruiser top speed??

I have a 1990 18' maxum with a 3.0L alpha 1 out drive I'm running with a 14x20 4 blade prop, I'm on plain with in about 5 sec top speed is 42mph @ 4800rpm's with 2 adults.

 

[Bifflefan]

Re: 3.0 mercruiser top speed??

Theoretical Boat Speed Equation:

RPM / Gear Ratio x prop pitch / 1056 = Speed

Copied from Cabela's .com

This is not an absolute but more what it would be if all were perfect.

 

[bigskiohio]

Re: 3.0 mercruiser top speed??

you need a 19 pitch prop to give you all around performance.