3.0 Mercruiser prop.

Jgrinds68

Cadet
Joined
Jul 6, 2015
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13
I am a first time boat owner, I bought a 1995 Regal Valanti 182se. 3.0 mercruiser Alpha 1. 14.5 19" prop. last fall. We have had the boat out several times with just me and the wife or me the wife and 1 of our kids. we had the boat out once with 4 adults and the boat has done great everytime. this past weekend we asked a couple freinds out on the lake with us for the Holiday. we had 6 adults, 3 large coolers, plus food and towels and stuff and the boat would not get out of its own way. it struggled to do 15 MPH. and I could not get over 3000 RPMs. the engine runs great. I am very mechanical, I have restored the boat paint and I replaced the prop. with one just like was on it before. I can understand the boat being slower with that many people in it, but i did not expect it to be as bad as it was. is it just the prop? has anyone else had this happen? thanks
 

Alumarine

Captain
Joined
Feb 22, 2005
Messages
3,684
I'm guessing it's an 18ft fiberglass boat?
That sounds normal with that load and that motor.
If it's a bow rider get as much weight forward when trying to plane. It might help.
Are you sure you're not overloaded?
It might even be waterlogged.
Oh, and welcome!
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
We need the wot rpm and gps speed with you and the wife.
If your not over loading with that crowd you could try a 17" pitch.
But I'd like to see the wot numbers first.
 

Jgrinds68

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Jul 6, 2015
Messages
13
Never had to have it WOT before. It will do 35 easy and about 4000 RPM with me and the wife and not be at WOT. I was thinking it was over loaded also, but only 6 adults on a 18 ft. Boat that holds 8?
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I think boat capacity is rated at 140 lbs for an adult.It does seem that other than the struggles with a load your set up well.
It is important that the motor be able to operate within its rated wot rpm. We need the gps speed to evaluate the whole setup.
It's entirely possible that if you and the wife are at say 4300 or 4400 at wot your barely in the power curve and when you add weight
it will fade quicker obviously dropping further out of the range.Selecting a prop is like trying to find a single gear to do it all in a car.
Marine motors are working very hard like a car pulling a trailer up a never ending hill in high gear. If your at the low end of the wot
rating it's kind of like putting the car into over drive on that hill.
 

Jgrinds68

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Jul 6, 2015
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13
Ok thank you so much. I weigh 250 and the other two guys were 200 plus also.

I see where it appears a 19" prop is great for touring, and they say to switch to a 17" for more power, would a 18" not give you a little of both?
 

airshot

Rear Admiral
Joined
Jul 22, 2008
Messages
4,219
Yes the little 3.0 is not the strongest engine out there but with the correct selection of props you can make it work well. I carry two props, one for normal cruising and fishing and another for heavy loads. You will need to know your wot rpm for each situation so you can prop correctly. It takes less than 5 min to switch props while the boat is getting ready to launch.
 

Jgrinds68

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Jul 6, 2015
Messages
13
Ok, tested boat today. Me @ 250 pounds, my wife 140, daughter at 120, 9 pound dog and small cooler. At WOT boat maxed out at 3700 RPMS and 27 MPH by GPS speed. It has a 14.5" x 19p prop. What do you suggest I change the prop to?
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
That's a pretty light load, and if you weren't in the ball park on WOT RPM, you have other issues. IE: water logged foam and/or water in hull, mechanical issues. I would weight the boat to rule water intrusion (see manufacturer for original weight), then do a complete tune-up including all filters in the fuel system.

I'm guessing that vintage of 3.0L has a WOT RPM of 4400-4800 RPM, and to put the engine in the middle of that range you would need to drop to a 15P prop. Though, I wouldn't recommend a 15P prop, unless it's for a heavy load (which your wife/kid/dog test wasn't) or for high altitude....... BTW, what altitude are you running the boat.....
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Ok, tested boat today. Me @ 250 pounds, my wife 140, daughter at 120, 9 pound dog and small cooler. At WOT boat maxed out at 3700 RPMS and 27 MPH by GPS speed. It has a 14.5" x 19p prop. What do you suggest I change the prop to?
Your numbers are fairly consistent but the boat is struggling speed should be over 30 maybe even close to 40.with rpm over 4000.
Before selecting a prop you should confirm the motor is in full tune.Check the simple stuff.Does the throttle open all the way.Does the boat respond to up trim?
Do you trim down for hole shot?
good compression?Timing set right and advancing as it should?Bottom clean and smooth?Prop in good condition?
Running on all cylinders?Does the boat get up on the water as it should or does it lay down like it's glued to the water ?
Perhaps even steering oddly?Is there a hydrofoil on the leg?
If you plan to run with a similar load a 17" pitch would probably put you at about 4100.As it stands still not enough.
Before any changes check the things I suggested.
 

philipp10

Seaman
Joined
Aug 8, 2012
Messages
61
I have a very similar sized boat with the 3.0. With 3 adults I can run a 14.25 x 19 and hit 4800 or run a 14.25 x 21 and hit 4400. If your only hitting 3700 rpms, something is not right. Either boat is waterlogged or more likely, your motor is not running right. I would expect your setup to be hitting a minimum of 4100 WOT.
 

Jgrinds68

Cadet
Joined
Jul 6, 2015
Messages
13
Ok, checked the ignition parts. and they were not in good shape. I did a full tune up, cap, rotor, plugs and wires. also ran some sea foam through the Carb. took the boat back out but this time with both my daughters which added another person and about another 135 pounds to the load. I was able to get the boat up to 4000 RPMs and WOT. my speed was at 28 MPH at GPS speed. I havent checked compression or gas pressure yet. I will probably leave it like this the rest of the summer and this winter take a look at compressiona and stuff. thanks for the help.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
At some point we still need a lightly loaded wot test run. That would be you alone.
Your 3.0 in a 18 footer should be at or about 4800 rpm with you alone.
Without that light test run we can't tell if your propped within the rpm range.
You need to make 4400 rpm with just you in the boat.To get
you in the very bottom of the range. Even though a 19 is a normal prop
if the boat can't make the rpms it's just like you have installed the wrong prop.
Your test run at 700lbs load does indicate something other than a prop problem.
Enjoy your boat but when you get to it check the timing and be sure it advances as it should.
You might consider a 17" pitch to ease the strain on your motor.
 

Jgrinds68

Cadet
Joined
Jul 6, 2015
Messages
13
I did notice something during the test. It was hard to run the boat at WOT. If I push it to WOT, then pulled the handle back about an inch the RPMS went up a couple hundred and the boat speed up, if I pushed it back down to WOT iyou could feel the motor flatten out and the RPMS went down a little.
I will check the timing. How would I know if it was advancing?
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Timing should advance as you increase the rpm.just watch it.
​ Timing may advance electronically,but you nerd to see that it does.
 

Jgrinds68

Cadet
Joined
Jul 6, 2015
Messages
13
hello, I just wanted to up date this post. I have posted a few other topics on our forums and one was dealing with my loss of power at WOT. This seems to be more of my issue then the pwop. It appears i have a fuel system issue. I plan on replacing the fuel pump and rebuilding the carb to see if this fixes the issue. thanks everyone who helped me out. I ahve learn alot about boats and their engines.
 

wahlejim

Master Chief Petty Officer
Joined
Jul 23, 2015
Messages
884
If your RPMs are dropping at WOT, that indicates a fuel supply issue. When is the last time you changed the fuel filter? When you used sea foam, did you run it through the tank or directly through the carb? If you run it through the tank, sometimes it cleans out gunk in your fuel lines and plugs up the filter. Your boat should not be losing RPMs at WOT. Fix the engine first before you try to mask the problem with a different prop.
 
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