www.iFourWinns.com

I have read there are not too many OB owners on here but I'm hoping there are enough to help.

I'm having some running issues that I'm trying to diagnose, which I won't go into just yet, but my question is this...

I have a 1999 Horizon 180 BR with a 2000 Johnson 130 Ocean Pro. It has an Aluminum 14.5 x 19 prop. The highest RPMs I can get is 4300 whereas the specs say I should be getting up to 5500. My speedo says a shade over 40 mph and my GPS says 38 mph (I was going upstream so sounds about right). How does this compare with anyone else with my setup?

Thanks guys

Based on a quick prop slip calculation, it seems your RPM/Tachometer are not correct. You need to double check the tach either with a small portable one or a new one.

Your engine has either a 2.00 or 2.25 gear ratio. If you are getting ~39 mph at only 4300 RPM you have NEGATIVE prop slip, which is impossible. You should be in the 10-20% prop slip range....which would mean you are likely turning 5300-5500 rpm. You will need to confirm which lower unit/gear ratio you have also.

Here is one calculator to use: http://www.mercuryracing.com/prop-slip-calculator/

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Current Operational Boats:
'04-Four Winns 180 Freedom 150 HP Evinrude
'72-Chris Craft Commander 31 Sedan Twin-350Qs

Thanks for the quick response.

I should have mentioned... With the boat on the water a did check the RPM with a handheld digital tach. I tested at 1000, 2000 and 3800 (I was aiming for 4000 but couldn't get it to stay there on my own ) Through that range it was pretty much bang on. Now I don't know what to make of it.

Well, I guess you need to get a second person to run the boat while you watch your portable tach....

Do you know what the gear ratio is in your lower unit?

_________________
Current Operational Boats:
'04-Four Winns 180 Freedom 150 HP Evinrude
'72-Chris Craft Commander 31 Sedan Twin-350Qs

I think 2.00:1 but I'm not sure. How would I determine that?

If you know that the lower unit is original to the motor then you should be able to just confirm with the model & serial number to see what ratio it is. If the lower unit was ever replaced and you don't know, you will need to spin the prop shaft and see how many times it goes around for a given number of turns on the flywheel.

You can pull the plugs then mark the prop and flywheel then spin the prop some number or times...perhaps 20 and have someone else count how many times the flywheel turns. Then just divide. There are only 3 likely options that I am aware of for that motor/gear case. 1.86, 2.00 or 2.25.

_________________
Current Operational Boats:
'04-Four Winns 180 Freedom 150 HP Evinrude
'72-Chris Craft Commander 31 Sedan Twin-350Qs

As far as I know it's original but can't be 100% I'll spin it up tonight and see what it is.

Thanks

Still not sure about the whole prop slip thing but, based on advice I received, I replaced my prop (14-1/2x19) with a 15x17. OMG what a difference! The boat gets on the plane like a raped ape and I hit, just shy of, 5500 rpm and still managed to get just over 40mph. I cannot believe the difference.

It sounds like there was something wrong with your 14.5 x 19" prop. There should not be a 1200 rpm difference between these two props. Perhaps it was modified to a higher pitch, cupped and/or was distorted from a past impact. If you ever get the chance to try a newer 14.5 x 19 I bet it would have a better result than your old one.

If "just shy of 5500 rpm" is in your recommended wide open throttle rpm for this engine, then it sound like you found the right prop with your new 15 x 17"

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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

The 14.5 x 19 was brand new too. I bought it to replace the one that came with the boat/motor as it had a few dings in it. Both new props are the same brand (Michigan Wheel) from the same supplier.

According to my tach I was getting somewhere in the range of 5300 to 5400 since the spec for the motor is 5500 I figured that was close enough. If we assume I was getting 5300, that's an increase of 1000 rpm. I know, in theory, I should have gained around 400 so I can't explain the increase in revs I just know that what happened.

Glad you found a solution.

Are the 2 props the same "model" of Michigan Wheel props?

_________________
Current Operational Boats:
'04-Four Winns 180 Freedom 150 HP Evinrude
'72-Chris Craft Commander 31 Sedan Twin-350Qs

I have to assume so, they are both Vortex A. The 19" is a 992004 and the 17" is a 992003

Thanks, no one is as glad as I am. It was driving me nuts. I pleased on two levels. One, it looks like the problem is solved and it wasn't a major engine issue and two, the way the boat gets up now is ridiculous. I must have stopped and started 20 times yesterday just for fun