2000 Johnson 150hp Oceanpro Prop Slip

[reiddo1]

I have a prop (part number 390821) on my 2000 Johnson Oceanpro 150 hp engine. This prop is a counter clockwise rotating one. My calculated slip is close to 30% using the tachometer and GPS speed over ground information. I have called Solas, gave them the prop part number from the hub and they told me that the prop I am using would be the original prop which they supplied to OMC. When I spoke with them I did not know that my slip was that great. The slip does not change from 3500 to 5200 WOT. I would like to lower my slip and hopefully reduce my fuel consumption. Does anyone have any ideas on which prop I should be using?

 

[reiddo1]

ANYONE???

 

[GA_Boater]

Please don't yell at us!

Read this - http://forums.iboats.com/forum/gene...-and-topics/295058-read-this-first#post295058

 

[reiddo1]

I have a prop (part number 390821) on my 2000 Johnson Oceanpro 150 hp engine. This prop is a counter clockwise rotating one. My calculated slip is close to 30% using the tachometer and GPS speed over ground information. I have called Solas, gave them the prop part number from the hub and they told me that the prop I am using would be the original prop which they supplied to OMC. When I spoke with them I did not know that my slip was that great. The slip does not change from 3500 to 5200 WOT. I would like to lower my slip and hopefully reduce my fuel consumption. Does anyone have any ideas on which prop I should be using?

My boat is a 1979 Glastron v216 Sea Fury with a manufacturer's dry weight of 2200 pounds. Hull is clean below waterline with no,

 

[reiddo1]

Should read that my boat is a 1979 Glastron v216 Sea Fury weighing 2200 pounds and no waterlogged foam. The hull is clean below the waterline with no bottom paint and is very straight and true. I wish to have the current prop which is a Solas 14.5 by 19 pitch changed to one which is more efficient. Please read the first post along with this one and offer me your comments. I appreciate all forms of input here.

 

[Sea Rider]

What's the max wot rpm range for that OB, assume stated 5200 rpm is not so ?

Happy Boating

 

[reiddo1]

OMC stated operating range is 4500 to 5500 rpm. I currently get lightly loaded 5200 rpm.

 

[Texasmark]

Go to: http://www.go-fast.com/Prop_Slip_Calculator.htm. Does that calculate to 30%? Your rpms are ok in that your selection of props is limited by the fact that most change pitch in 2" increments. Is that Solas SS? Is it cupped?

 

[Sea Rider]

Theoretically speaking going one pitch less will manage to run near or at its max stated wot rpm range. You like or intend boating light, medium light of fully loaded. It's not same matching a only one prop while boating with such weight differences. Could send current prop to a prop shop and have it repitched to an 18 one. Will work much better than with current 19, provided that deck weight is maintained same.

Happy Boating

 

[reiddo1]

Theoretically speaking going one pitch less will manage to run near or at its max stated wot rpm range. You like or intend boating light, medium light of fully loaded. It's not same matching a only one prop while boating with such weight differences. Could send current prop to a prop shop and have it repitched to an 18 one. Will work much better than with current 19, provided that deck weight is maintained same.


Can the alteration to 18 pitch be easily made to a stainless prop and how is a reduction in pitch going to reduce the slip? I realize the RPM at WOT will probably jump to the maximum for its operating range, but how do I get more grip from that prop?

 

[Sea Rider]

Assume that will need to sit OB at the sweet tarnsom height, for prop to grip better. Post a pis of lower leg showing upper and lower horizontal plates to work from there.

BTW, how did you ended with a CCW rotating OB, was part of a dual set-up.

Happy Boating

 

[reiddo1]

Assume that will need to sit OB at the sweet tarnsom height, for prop to grip better. Post a pis of lower leg showing upper and lower horizontal plates to work from there.

BTW, how did you ended with a CCW rotating OB, was part of a dual set-up.

Happy Boating

The engine has been with me for 4 years and I suggest it indeed was part of a dual setup. It was rebuilt before I acquired it by Marine Medics in Ontario. I have it mounted so that the anti ventilation plate is 3/4 inch above the keel using straight edges for measurement. I have moved to that height position largely because of recommendations from this site and believe my adjustments to the top hole have made improvements. When at WOT I can barely see the anti ventilation plate.
I only see a huge increase in engine speed when I trim out considerably. With a "proper" trim I will get prop revving only when doing hard turns on the helm at full speed. I really am happy with the boat operation. My slip calculates the same at cruise as at WOT. Thank you for your interest in my problem..

 

[Texasmark]

Mind answering my questions?

 

[reiddo1]

Go to: http://www.go-fast.com/Prop_Slip_Calculator.htm. Does that calculate to 30%? Your rpms are ok in that your selection of props is limited by the fact that most change pitch in 2" increments. Is that Solas SS? Is it cupped?

Sorry I did not see your post until now.
Slip Calculates to 29%. Am no expert on props cupping but it does not appear to be. All Solas told me is that it is theirs and is no longer produced. Solas recommended a 4 blade prop and 17 pitch but did not address slip/cupping specifically. They said a 4 blade Rubex HR4 would work better for me but I would probably lose on top end speed. Thanks for you interest.

 

[reiddo1]

Mind answering my questions?

Yes the prop is stainless steel.

 

[Texasmark]

Yes the prop is stainless steel.

Ok that solves that potential fix and I'll assume cupping is there too as is usually used with SS props. So, next question, did you play around with the prop slip calculator? Learn anything? Questions?

 

[reiddo1]

Ok that solves that potential fix and I'll assume cupping is there too as is usually used with SS props. So, next question, did you play around with the prop slip calculator? Learn anything? Questions?

I did not need the calculator to calculate my slip but it reinforced what I had already calculated manually. I am wondering if it is possible that my specified gear ratio at 1.85:1 might be 2.25:1 as it was for some OMC lower units. Using that ratio places me with a very good slip indeed. Also I am wondering if the gear ratio is as specified, then maybe using a 1979 vintage Glastron hull might indeed be causing that high slip. The 150 Oceanpro is a wonderful engine; I am not concerned too much with the speed but I would like the assurance that with my current prop and operating parameters, I am operating most efficiently. The engine is a pig on fuel and I think the slip has a lot to do with it. Low RPM torque is superb, Engine starting is wonderful and other than having it underwater last year for 4 hours along with the associated problems, this engine has been a dream engine from a maintenance perspective.

 

[Texasmark]

Don't have to guess. Prop turns slower than the crankshaft by the ratio. Mark the flywheel and the prop. If you measure the circumference of the flywheel, you can mark off the distance and convert to a percentage of a revolution. 2:1 is easy, the flywheel has to turn 2x360 for the prop to turn 360. If the ratio is 1.xxxx:1 the flywheel won't quite make the second 360.

Say the flywheel is 12" dia. Pi x D is 37.7". Say on your second revolution you only get around 28.3" of the 37.7" full revolution. 28.3/37.7 = .75. the ratio is 1.75:1.

 

[reiddo1]

Don't have to guess. Prop turns slower than the crankshaft by the ratio. Mark the flywheel and the prop. If you measure the circumference of the flywheel, you can mark off the distance and convert to a percentage of a revolution. 2:1 is easy, the flywheel has to turn 2x360 for the prop to turn 360. If the ratio is 1.xxxx:1 the flywheel won't quite make the second 360.

Say the flywheel is 12" dia. Pi x D is 37.7". Say on your second revolution you only get around 28.3" of the 37.7" full revolution. 28.3/37.7 = .75. the ratio is 1.75:1.

Yes, that indeed is my next step and over the next week, I hope to confirm that it is a 1.85:1 ratio. Thanks again.

 

[Texasmark]

On slip and prop pitch, think about it. If the prop is operating near the surface, the distance from the density of water to the density of air is in the inches or fractions thereof. When you use a shallow pitched prop, the distance traveled per revolution is minimal so the force exerted against the water (thrust per rpm) is reduced meaning that there isn't much pressure differential between the rear of the blade and the ambient air. As the pitch is increased, that thrust per rpm is increased and there is more of a suction from the prop which, when adequate reaches through the available water to the ambient air and you have ventilation. Ventilation is a form of prop slip. The other part is how fast you can move the water before it forms a vacuum and the density of the water is reduced (addition of bubbles) reducing the available thrust.....cavitation. The lower the pitch the lower the water movement per rpm, the lower the cavitation.

Light, fast boats can move water very fast and have little slip. Barges can't and do!