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Author Topic:   18 Outrage/140 Johnson - prop size dilema?

HJB posted 05-20-2003 09:02 PM ET (US)
I own a 1989, 18 Outrage with an 89 Johnson 140 ob. I need a correct prop size, to maintain plane at "lower" speed(s). I currently have to cruise around 3600 rpms to stay up on plane. Anyone own this boat setup, and can assist on my planing dilema?
acseatsri posted 05-20-2003 09:36 PM ET (US)
I have the same with a 150, had the same problem. That vintage OMC didn't have enough negative trim possible. I installed a Doelfin and transom wedges, dropped about 4-5 knots off my planing speed. You could probably obtain better results with trim tabs, but it would also cost a lot more, probably around $400+ for the tabs vs about $40 for fin and $30 for wedges. I also moved the batteries to the console, though mainly to help offset the weight of a kicker on the transom.
PS- with the 150 Hp and engine trimmed all the way in, I can plane at around 2600 RPM. A lower pitch prop may also help in keeping on plane.
FLUKEDUKE posted 05-21-2003 12:34 PM ET (US)
My 88 OR18 with a 150 has a 14 1/2P x 19D SS cupped prop. With battery, kicker/3 gal. tank and 20 gal. livewell all in the back, it is in plane at around 3000 +- 100 depending on conditions, POB and wether the livewell is full. All this may not be relevant to your case with a 140, even though there's only 10 hp difference there is a big difference in the 2 motors. The 140 was at that time a "high tuned 4 cyl" to generate the 140 rating, whereas the 150 was a "low tuned 6 cyl" to produce 150 hp., meaning the hp to RPM curves are quite different for each engine. Sorry I can't help with the best prop size for your set-up but I'm sure there's someone on this site who can.
Tom2697 posted 05-21-2003 01:33 PM ET (US)
A lower pitch prop should get you on plane quicker and maintain plane at a lower RPM. However, you will lose top end and might even overspeed the motor. For a better answer, we will need more info on your setup. What is you WOT and your current prop size? Are you running a 3-blade or a 4-blade? Stainless or aluminum? Cupped or uncupped? What is your normal load? etc.
Also, if you don't have a Dowl-fin installed already, you might want to give one a try. They were designed for this problem.
Barry posted 05-21-2003 03:13 PM ET (US)
How high is your engine mounted? The anti-ventilation plate should be at least even with the bottom edge of the hull and preferably 1-2" above it. See this for more info http://continuouswave.com/ubb/Forum4/HTML/001644.html
gfrutig1 posted 05-21-2003 04:23 PM ET (US)
I have the same motor on 83 18 Outrage. I have 2 props I run, 19 and 21 inch pitch, both stainless and cupped. 19 will plane at lower speed, but will exceed rpm with light load. 21 will fly, but slow out of hole. Our lower unit is consderably smaller than those on most 150's out there. hope this helps.
Gary
Sal DiMercurio posted 05-21-2003 06:58 PM ET (US)
Flukeduke, your prop is a 14.1/2D x 19P, no such prop as a 19d x 14-1/2p.
Don't under estimate those 140s, they were hot engines.
HJB, you don't say which prop your now running, pretty tough without knowing what you have.
Sal
jimh posted 05-21-2003 09:30 PM ET (US)
What is the point of having a forum specifically for discussion of "performance" which has hundreds of article about propeller selection if we are all now suddenly content to post and answer these questions to the General forum?
I don't at all encourage this type of posting and in fact I tend to delete them after a day or two.
If you want help with your boat's performance, please post your article to the Perforemance forum, where it will be archived and provide useful information for others.
Articles posted to the general forum which are more appropriate elsewhere will not be archived.

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Author	Topic: 18 Outrage/140 Johnson - prop size dilema?
HJB	posted 05-20-2003 09:02 PM ET (US) I own a 1989, 18 Outrage with an 89 Johnson 140 ob. I need a correct prop size, to maintain plane at "lower" speed(s). I currently have to cruise around 3600 rpms to stay up on plane. Anyone own this boat setup, and can assist on my planing dilema?
acseatsri	posted 05-20-2003 09:36 PM ET (US) I have the same with a 150, had the same problem. That vintage OMC didn't have enough negative trim possible. I installed a Doelfin and transom wedges, dropped about 4-5 knots off my planing speed. You could probably obtain better results with trim tabs, but it would also cost a lot more, probably around $400+ for the tabs vs about $40 for fin and $30 for wedges. I also moved the batteries to the console, though mainly to help offset the weight of a kicker on the transom. PS- with the 150 Hp and engine trimmed all the way in, I can plane at around 2600 RPM. A lower pitch prop may also help in keeping on plane.
FLUKEDUKE	posted 05-21-2003 12:34 PM ET (US) My 88 OR18 with a 150 has a 14 1/2P x 19D SS cupped prop. With battery, kicker/3 gal. tank and 20 gal. livewell all in the back, it is in plane at around 3000 +- 100 depending on conditions, POB and wether the livewell is full. All this may not be relevant to your case with a 140, even though there's only 10 hp difference there is a big difference in the 2 motors. The 140 was at that time a "high tuned 4 cyl" to generate the 140 rating, whereas the 150 was a "low tuned 6 cyl" to produce 150 hp., meaning the hp to RPM curves are quite different for each engine. Sorry I can't help with the best prop size for your set-up but I'm sure there's someone on this site who can.
Tom2697	posted 05-21-2003 01:33 PM ET (US) A lower pitch prop should get you on plane quicker and maintain plane at a lower RPM. However, you will lose top end and might even overspeed the motor. For a better answer, we will need more info on your setup. What is you WOT and your current prop size? Are you running a 3-blade or a 4-blade? Stainless or aluminum? Cupped or uncupped? What is your normal load? etc. Also, if you don't have a Dowl-fin installed already, you might want to give one a try. They were designed for this problem.
Barry	posted 05-21-2003 03:13 PM ET (US) How high is your engine mounted? The anti-ventilation plate should be at least even with the bottom edge of the hull and preferably 1-2" above it. See this for more info http://continuouswave.com/ubb/Forum4/HTML/001644.html
gfrutig1	posted 05-21-2003 04:23 PM ET (US) I have the same motor on 83 18 Outrage. I have 2 props I run, 19 and 21 inch pitch, both stainless and cupped. 19 will plane at lower speed, but will exceed rpm with light load. 21 will fly, but slow out of hole. Our lower unit is consderably smaller than those on most 150's out there. hope this helps. Gary
Sal DiMercurio	posted 05-21-2003 06:58 PM ET (US) Flukeduke, your prop is a 14.1/2D x 19P, no such prop as a 19d x 14-1/2p. Don't under estimate those 140s, they were hot engines. HJB, you don't say which prop your now running, pretty tough without knowing what you have. Sal
jimh	posted 05-21-2003 09:30 PM ET (US) What is the point of having a forum specifically for discussion of "performance" which has hundreds of article about propeller selection if we are all now suddenly content to post and answer these questions to the General forum? I don't at all encourage this type of posting and in fact I tend to delete them after a day or two. If you want help with your boat's performance, please post your article to the Perforemance forum, where it will be archived and provide useful information for others. Articles posted to the general forum which are more appropriate elsewhere will not be archived.