Ribcraft 585/150 Evinrude prop size help!

JABS · 25 March 2008, 22:13

Hi,

I just changed the engine on our Ribcraft 585 to an Evinrude Ficht 150 two stroke. Has anyone experience of that combination and can you offer advice on prop choice? I have tried 23 and 20 pitch and am still struggling to achieve WOT. Could I have a fuel starvation issue???

Thanks.

Tony.

Hightower · 26 March 2008, 19:29

Facts and figures is what we need. What revs and speed is she pulling at WOT.

I have a 150 FICHT too, she pulles about 5000RPM and acheives about 40knotts with a 19" prop on a 6.2m. You should be getting about 44knotts of speed at least with a 5.85.

JABS · 26 March 2008, 20:49

First run was with a 23 inch pitch p[rop. I got 4000 RPM and 39 knots. Fairly calm conditions.

Put on a 20 inch pitch and, although it was too rough to go balls out for long, was only getting around 4300 and no more speed.

I need to do a run on the 20 inch prop in calm conditions, but I think it is still too coarse.

I have been offered a 19 to try and think that looks promising.

23 an 20 are stainless, 19 is ally. Is that a problem??

Speed as measured on GPS, on the 23 in two directions. On 20, only one way in S'hampton water, so could have been a knot or two against me.

Didn't want to get into so much detail initially.

Thanks for your help.

Tony

Neil Harvey · 26 March 2008, 21:04

Tony, You are welcome to try my 19" stainless at some point if it helps.
I went from a 19" that had me pulling over 6000 rpm to a 21" pulling about 5800-6000, that's on a 175 DI and 7.2m rib.

Hightower · 26 March 2008, 21:44

Don't forget that the 175 has a higher WOT throttle range than the 150 which is 4750-5250.

Are you sure there's no extra weight on the RIB like a bilge full of water?

My speed drops to about 37 knotts with 2 up and 200 litres of gas on board, revs drop to around 4800rpm trimmed right out.

When I used the 21" prop the speed was pretty good at about 42 knotts and the revs dropped to 4400.

The other thing that you can check easy is the throttle is opening fully when the throttle handle is fully forward.

Hope that helps a little more.

JABS · 27 March 2008, 07:37

Quote:

Originally Posted by Neil Harvey

Tony, You are welcome to try my 19" stainless at some point if it helps.
I went from a 19" that had me pulling over 6000 rpm to a 21" pulling about 5800-6000, that's on a 175 DI and 7.2m rib.

Neil,

Would love to try that prop.

I hope, this weekend, to try the 21 in calm conditions, even if I have to go up to the container basin. That will give me a final result on the 21. Then it could be time to go to 19. Thanks Neil.

Hopefully more on Monday.

Thanks for all the help. RibNet is a truly valuable resource.

Tony.

JABS · 27 March 2008, 07:39

Quote:

Originally Posted by Hightower

Don't forget that the 175 has a higher WOT throttle range than the 150 which is 4750-5250.

Are you sure there's no extra weight on the RIB like a bilge full of water?

My speed drops to about 37 knotts with 2 up and 200 litres of gas on board, revs drop to around 4800rpm trimmed right out.

When I used the 21" prop the speed was pretty good at about 42 knotts and the revs dropped to 4400.

The other thing that you can check easy is the throttle is opening fully when the throttle handle is fully forward.

Hope that helps a little more.

Andy,

We dry sail, so don't think we have a bilge full, but that is a valid point which I will check.

The tests so far have been done with one up and 80 litres of fuel. Nothing else of note on board, except the results of many beers over the years!

I need to have a definitive run with the 21, hopefully this weekend.

Thanks for your help, Andy.

Hightower · 27 March 2008, 19:30

Well check the throttle, that's easy. Fully open the throttle lever on the console and see if there is anymore travel in the linkage under the cover (butterfly valves horizontal).

one easy method of discovering whether the outboard is being starved of fuel is to go WOT on a cruise and get someone to pump the primer bulb. If you get extra performance when the primer bulb is being pumped then the answer is yes, if you don't you keep looking.

One other performance area to look at is the height of the outboard relative to the hull bottom. Too much outboard leg in the water will cause drag and slow the boat, so check that too this weekend too.

Downhilldai · 27 March 2008, 23:24

Who fitted the motor? Do they have facilities for you to test different props?

The WOT RPM sounds low to me for such a high power o/b on a light boat. Set-up may need looking at, as Hightower says above.

JABS · 06 April 2008, 19:50

We finally got some WOT running on the 20 inch pitch ss prop on Saturday. We achieved 4400rpm but had a GPS failure so can't report the speed attained. Even at the top end of Southampton Water, in calm conditions, we didn't gtet above 4400.

The boat jumped up onto the plane easily and was very responsive.

Could the Tacho be out??

I now have the 19 pitch prop in the car, ready to try. I don't want to risk over revving the outboard.

Is the general opinion that we have another issue to address???

Thanks

Tony

Neil Harvey · 06 April 2008, 19:55

I don't think you are pulling nearly enough revs.

Like you said, maybe the tacho could be out. If you think that's a possibility, best to get it checked out rather than risk over revving.

Does not sound right though, so if it were me, I'd take it back if you bought it from a company as opposed to private.

They should at least be able to attach it to the computer and see what it is running at. If the tacho is correct, I would have thought there is definitely something wrong.

good luck!

Chris · 07 April 2008, 19:53

There is normally a switch on the back of the tacho that you set for either 3/4 or 6 cylinder engines.

It may be this needs setting correctly.

Chris · 07 April 2008, 20:00

Tony, I assume you are trimming out to get full speed?

Chris

antoine · 07 April 2008, 20:55

Hello,

A french ribs fan wich have a Tornado 580 with a 150 etec tried a lot of prop.

You can see the results her :http://img412.imageshack.us/img412/6...cesjpegiy6.jpg

He talk about it here
http://pneuboat.com/serv-bibl/module....php?id=207536

I'm sorry, it's in french but tou can find few ideas, i think.

Antoine

Hightower · 07 April 2008, 21:06

Try This: http://babelfish.altavista.com/babelfish/tr

might make things a little clearer.

antoine · 07 April 2008, 21:18

Great!

The first day:

First assembly which I will name "race": height + 6-7 cm (driving shift +3 cm), Propeller Rebel stainless: 14.3/4 X 23: The boat seems very on-motorized, it has a very unstable behavior that I never knew to him with the 115 Ficht, the trim is practically not exploitable! The perfs are on the other hand époustouflantes in the low modes, 30 KT to 2500 T, one pushed it up to 48 KT for hardly more 4000T... but beyond that, it seemed ingérable and dangerous! I was thus a little depity of the nonhomogeneity of the ensemble..et especially I did not recognize my hull at all that I know so sure and effective.....

Second assembly: even propeller, even shift, but height brought back to + 4-5 cm the behavior of the unit very clearly improved, that always pushes very extremely, but the hull is much more stable and remains.... the push well flat is objectively phenomenal, I already used ribs which take more than 50 KT, but none had given me this feeling of "fulgurance", the 0-40KT is reached in a few seconds and less 50m I think! Side perfs: 32 KT to 3000 T, 42 KT to 4000 T, but there the boat remain well on line and very stable up to 45-46 KT, then, the hull is on a wire, it is very unstable, one pushes until practically 50 KT and approximately 4600-4700 T with the max, trim positive! It is thus much better, but very perfectible.....il remains 1000T under the cap and still a hair of instability to try to recover... if the hull (of a SR of less 6m...) to little support such dash speeds without stumbling?

New test:

Assembly +4-5 cm (not of change thus...), but this time with a very different propeller, more dedicated at the speed 14 3/4 X 21 Viper stainless: The behavior of the boat is very different as of the "setting in catch from the engine", paradoxically, whereas the step decreased one feels much less the important couple of the engine... dans trés low the modes (- of 2000 T), the nose of the boat is raised much more and the unit is much less "fluid"..... The perfs are very in withdrawal, one is more than to 25 KT to 3000 T and hardly 32 KT to 4000 T (against 42 with the 23 with the same mode!!)..la dash speed is it also penalized with 46 KT and always of the instability, which appears there besides rather, towards 44 KT! 5200 T on the other hand are reached (one took from 300 to 400 T) what was partly the required goal... mais the boat is less pleasant, less powerful (not more nervous of the whole!) in all the compartments, and especially less stable! "very basic" assembly, one descends the engine from a hole is: +2-3 cm with return to 14 3/4 X 23 Rebel of the departure: One finds a more pleasant unit, with an enormous couple in the low modes while leaving the hull very flat, a kick in the ass chabalesque, and perfs nearly identical to the first tests taking into account the water level and different conditions... soit 30 KT with 3000T, 40 KT to 4000 T and especially a concrete profit of stability à.fond since the boat remains very stable up to 48 KT (against 45-46 before...) what will be besides its dash speed for approximately 4700 T!

I hope it will help you...

Antoine

Chris · 08 April 2008, 07:22

Quote:

Originally Posted by antoine

Great!

The first day:

First assembly which I will name "race": height + 6-7 cm (driving shift +3 cm), Propeller Rebel stainless: 14.3/4 X 23: The boat seems very on-motorized, it has a very unstable behavior that I never knew to him with the 115 Ficht, the trim is practically not exploitable! The perfs are on the other hand époustouflantes in the low modes, 30 KT to 2500 T, one pushed it up to 48 KT for hardly more 4000T... but beyond that, it seemed ingérable and dangerous! I was thus a little depity of the nonhomogeneity of the ensemble..et especially I did not recognize my hull at all that I know so sure and effective.....

Second assembly: even propeller, even shift, but height brought back to + 4-5 cm the behavior of the unit very clearly improved, that always pushes very extremely, but the hull is much more stable and remains.... the push well flat is objectively phenomenal, I already used ribs which take more than 50 KT, but none had given me this feeling of "fulgurance", the 0-40KT is reached in a few seconds and less 50m I think! Side perfs: 32 KT to 3000 T, 42 KT to 4000 T, but there the boat remain well on line and very stable up to 45-46 KT, then, the hull is on a wire, it is very unstable, one pushes until practically 50 KT and approximately 4600-4700 T with the max, trim positive! It is thus much better, but very perfectible.....il remains 1000T under the cap and still a hair of instability to try to recover... if the hull (of a SR of less 6m...) to little support such dash speeds without stumbling?

New test:

Assembly +4-5 cm (not of change thus...), but this time with a very different propeller, more dedicated at the speed 14 3/4 X 21 Viper stainless: The behavior of the boat is very different as of the "setting in catch from the engine", paradoxically, whereas the step decreased one feels much less the important couple of the engine... dans trés low the modes (- of 2000 T), the nose of the boat is raised much more and the unit is much less "fluid"..... The perfs are very in withdrawal, one is more than to 25 KT to 3000 T and hardly 32 KT to 4000 T (against 42 with the 23 with the same mode!!)..la dash speed is it also penalized with 46 KT and always of the instability, which appears there besides rather, towards 44 KT! 5200 T on the other hand are reached (one took from 300 to 400 T) what was partly the required goal... mais the boat is less pleasant, less powerful (not more nervous of the whole!) in all the compartments, and especially less stable! "very basic" assembly, one descends the engine from a hole is: +2-3 cm with return to 14 3/4 X 23 Rebel of the departure: One finds a more pleasant unit, with an enormous couple in the low modes while leaving the hull very flat, a kick in the ass chabalesque, and perfs nearly identical to the first tests taking into account the water level and different conditions... soit 30 KT with 3000T, 40 KT to 4000 T and especially a concrete profit of stability à.fond since the boat remains very stable up to 48 KT (against 45-46 before...) what will be besides its dash speed for approximately 4700 T!

I hope it will help you...

Antoine

Yes thats much clearer

Pikey Dave · 09 April 2008, 18:47

I had a Ribcraft 5.85 with a 175hp Ficht, which is basically the same engine as the 150. Initially I had a 20 inch prop on it. I couldn't get more than 4750rpm & low speed manouvering was a pain. I swapped it for a 19" & the difference was huge. 5500rpm, docile low speed response ( we used it as a dive boat so needed low speed for picking up divers) & 47kn top speed. All at around 4gph@30kn cruising.

JABS · 10 April 2008, 09:27

Tested last weekend on the 20 pitch prop and got 4400 WOT. GPS kindly packed up so I have no idea how fast we were going.

The boat gt onto the plane quickly but cavitated seriously in tight turns. Not sure if this is a clue.

Plan for this weekend is to fix the GPS and test with 19 and 20 props.

We also are going to visit the issue of engine height on the trasom.

Thanks to all.

Tony.

Hightower · 10 April 2008, 17:52

Quote:

Originally Posted by JABS

Tested last weekend on the 20 pitch prop and got 4400 WOT. GPS kindly packed up so I have no idea how fast we were going.

The boat gt onto the plane quickly but cavitated seriously in tight turns. Not sure if this is a clue.

Plan for this weekend is to fix the GPS and test with 19 and 20 props.

We also are going to visit the issue of engine height on the trasom.

Thanks to all.

Tony.

The prop caviteted with the engine trimmed in or out?