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Discussion Starter · #1 ·
After a few trip out on the boat with the new fuel flow guage I decided the prop on my outboard has got to be too small. I have a Arima Searanger 21 with a skip tower and a Yamaha Vmax 150. The current prop is a 13 3/4 x 17. At WOT the rpm guage reads right around 5700. My manual says that it should be between 4500 - 5500. The best fuel economy I can get is almost 2.5 mpg at 4200 rpm and 26 mph with my fising buddy and I in the boat, so I have a few questions I hope someone can help me out with.

1) Once my outboards reaches 5700 or so rpm I still have about 2-3" of throttle left. DO these motors have a govenor to prevent them from over speeding?

2) Does anyone know of a prop shop around Whidbey that will let you try a few different props before you buy?

3) I am thinking of going to a 14 x 19 prop and everything that I have read says it should reduce my top end rpm by about 200 but then I start to think about question 1 and then to question 2.

4) What is the advantage of a 4 blade prop over a 3 and vice versa?

Here is a pic of the boat and motor. Any help would be greatly appreciated. I would think I should be able to get around 3.5 mpg at a cruise of 3500 rpm and 28 mph.
 

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I have a 20' Trophy with a 150HP 1996 Yamaha. When I bought the boat (used) the max RPM's I could get was about 4700. I didn't know ant better as I had always owned I/O's and this my 1st outboard. When I took the boat in for service one time I mentioned the 4700. He told me that outboards are made to run higher RPM's and I should be geting closer to 5500 RPM's at top end. He also said the worst thing for an outboard is for it have too big a prop and which causes the engine to work too hard and lug. I went to a smaller prop and now I get 5300-5400 at top end depending my load. Boat performs much better out of the hole and good top end too. I can't comment on any gas comsumption difference because I don't know, and I probably don't want to know $$$$$.
 

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Call up the prop shop in mukelteo they sound very knowlegeable when I have talked to them
 

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Discussion Starter · #4 ·
I was wondering what some of the boards members that have simlar weighted boats and outboards where running? I have aslo heard that I do not want to bog the motor down but I sure as heck don't want to over rev it a bit more. If I can get the rpm down to near 5500 or slightly less than I would be happy.
 

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Fishfry, If you are really getting the kind of RPM you say then you are definitely under-propped.
There is a rule of thumb, 2 inches of pitch equals about 200 RPM. I am not sure about diameter. Try going to http://www.miwheel.com/MIWheel/propit/main.htm. This is a prop calculator and may be of some help.
 

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fishfry said:
I was wondering what some of the boards members that have simlar weighted boats and outboards where running? I have aslo heard that I do not want to bog the motor down but I sure as heck don't want to over rev it a bit more. If I can get the rpm down to near 5500 or slightly less than I would be happy.
I just went through this very same thing with my 22ft Sea Ledgend. I repowered to a 225 E-Tec & the 15x17 from my old 200hp was hitting 6200 on the new motor @ 43 mph 400rpm to much.

First prop was a 15.5 x 17 Rebel 5200 & 38 mph wot.
Second prop 14.75 x 19 SST 5400 & 40 mph
Third prop 14 1/8 X 20 4 blade Apollo 5600 & 41 mph vibrated bad
Fourth Prop 15.25x19 Apollo 3 blade 5700 & 44 mph Just Right
 

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If the current prop is in good condition,you can have the pitched changed by up to 2".

4 bladed props have better hole shot,better fuel economy,have better bite in rough water,and are also smoother running.

You'll lose top end with a 4 bladed prop though,because they have more drag.

4 bladed props typically run better closer to the surface,so you may have to change engine height with a 4 bladed prop.
 

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I forgot to add,you want to have the boat set up like it normally runs when making prop changes. If you add pitch and lower the rpms,then run with 4 guys when you tested with 2,you might lose too many rpms.
 

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Discussion Starter · #9 ·
I was wondering about the difference in load and weather or not the motor has a govenor in it. I can't seem to find it in the owner's manual because it will hit 5700 rpm with 2 adults, 2 adults and 2 kids and I have even had 6 guys in the boat and still hit 5700 rpm. I just want to be sure that I am still not going to be going too small by buying a 14 x 19. I guess I could get a cheeper aluminum one and see how that does then get a nicer SS one later. I will keep researching the governer question unless someone else knows. :geek:
 

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My boat is the Smaller 17' Arima with a 90hp Mercury. It came with a 21 pitch prop on it, and too all day to get on a plane. It would do about 31mph giving it all the RPM. I switched to a 19 pitch prop, and now she jumps out of the water better still runs around 31mph max RPM but now cruises nice at lower RPM's I normally cruise around 23mph. Seems to do ok on fuel. Sorry no more specifics on economy.
 

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fishfry said:
I was wondering about the difference in load and weather or not the motor has a govenor in it. I can't seem to find it in the owner's manual because it will hit 5700 rpm with 2 adults, 2 adults and 2 kids and I have even had 6 guys in the boat and still hit 5700 rpm. I just want to be sure that I am still not going to be going too small by buying a 14 x 19. I guess I could get a cheeper aluminum one and see how that does then get a nicer SS one later. I will keep researching the governer question unless someone else knows. :geek:
I'm thinking you need a new tach.

If you add 4 more adults and don't drop a few hundred rpms,I gotta think somethings wrong.

I've never heard of a 2 stroke with a governor,alot of 4 strokes have them though.
 

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No, the motors do not have a governor to prevent over revving. The over revving stops when the pistons exit the sides of the engine block. Also, it is my understanding that stainless steel props and aluminum props perform differently even if the pitch is the same. Another thing to keep in mind: Aluminum props can be repaired and rebuilt if damaged but stainless steel props have a tendency to shatter on impact. With all the logs and debris in the sound I prefer to stay with aluminum, they work fine and they are much cheaper. I would have to believe that if you went to a 14 x 19 that would be about perfect as you want to be able to develop 5500 rpm at WOT.
 

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Discussion Starter · #13 ·
Hunter P said:
fishfry said:
I was wondering about the difference in load and weather or not the motor has a govenor in it. I can't seem to find it in the owner's manual because it will hit 5700 rpm with 2 adults, 2 adults and 2 kids and I have even had 6 guys in the boat and still hit 5700 rpm. I just want to be sure that I am still not going to be going too small by buying a 14 x 19. I guess I could get a cheeper aluminum one and see how that does then get a nicer SS one later. I will keep researching the governer question unless someone else knows. :geek:
I'm thinking you need a new tach.

If you add 4 more adults and don't drop a few hundred rpms,I gotta think somethings wrong.

I've never heard of a 2 stroke with a governor,alot of 4 strokes have them though.
It may sound hard to believe but I consider myself a pretty good motorhead and 5700 rpm sounds the same with two or six in the boat. I will research it a bit more but I am sure the tach is reading correctly.
 

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Fishfry, this is a great topic and asking around at the boat shows I get all types of different answers. The problem with my 21 Arima SeaRanger with 130 HP Honda, I can't consistently get above 4800 RPM and I have a 12.75x17 4 blade. The general consensus for me was to go down to a 13x15 3 blade? So now I really am confused, especially reading your posts. Did you talk with the guys up at EQ Marine at Cornet Bay Marina? Les told me to go with the 15...
 

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catchinabuzz said:
Fishfry, this is a great topic and asking around at the boat shows I get all types of different answers. The problem with my 21 Arima SeaRanger with 130 HP Honda, I can't consistently get above 4800 RPM and I have a 12.75x17 4 blade. The general consensus for me was to go down to a 13x15 3 blade? So now I really am confused, especially reading your posts. Did you talk with the guys up at EQ Marine at Cornet Bay Marina? Les told me to go with the 15...
I'd be for getting the right prop ASAP. At 4800 you're 200 rpms under the MINIMUM specs for the 130. I'd want the rpms to be near 6000 at WOT with a 4 stroke. Lugging a 4 stroke is bad news. When you're at 4800,is that with the engine trimmed up?

I can gain almost 1000 rpms with my Yamaha 150 just by trimming the engine to the optimal trim angle.

If you were to switch to a 17" pitched 3 blade from a 17" 4 blade,you gain rpms just from the fact that the 4 blade makes more drag. Going to a 15" pitch should net you a few hundred more. I'd say going to the 15" pitched 3 blade should get you near 5400.
 

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Discussion Starter · #17 ·
catchinabuzz said:
Fishfry, this is a great topic and asking around at the boat shows I get all types of different answers. The problem with my 21 Arima SeaRanger with 130 HP Honda, I can't consistently get above 4800 RPM and I have a 12.75x17 4 blade. The general consensus for me was to go down to a 13x15 3 blade? So now I really am confused, especially reading your posts. Did you talk with the guys up at EQ Marine at Cornet Bay Marina? Les told me to go with the 15...
No I didn't talk to Les but I called Master Marine instead seeing as they deal with Yamaha motors. I talked a bit to their sales rep but their techs were out testing a boat so I will try again tomorrow. 4800 does seem quite a bit out of that motor. I am still trying to figure out why I have some 2-3" of throttle movment after I hit peek rpm with no change in rpm. It must already be a WOT before the throttle lever is all the way forward. I think I am going to try a 14x17 this weekend if I get out. They do not have a test prop program there but I am going with the aluminum prop so I won't be out a few hundred dollars if it is the wrong one. I love my Vmax it is a great performer but I think I can get a little better fuel economy out of it than I am now. Maybe not a whole mpg better but some.
 

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Go to a 19 pitch will push more water and handle a heavy load. Most Yamaha dealers offer a swap-a-prop where props can be returned for credit toward another prop. Must be new and in original box, when returned. Full throttle rmp range should be 4500-5500 that 19 pitch should provide good performance and should be all you need in rough water. You may want to go with a four blade instead. Call 253-891-0762 and ask for Brad he has a good selection 3 blade stainless and 4 blade Yamaha props store opens at 9am.
 

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I have tried trimming the motor to perfection, I get a little more top end speed, but only 100-200 rpms more. The other thing is I added trim tabs and maybe I just don't know what the heck I am doing with them. I have played around and haven't been able to create any more rpm....
 

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Discussion Starter · #20 ·
catchinabuzz said:
I have tried trimming the motor to perfection, I get a little more top end speed, but only 100-200 rpms more. The other thing is I added trim tabs and maybe I just don't know what the heck I am doing with them. I have played around and haven't been able to create any more rpm....
I can honestly say that the trim tabs used to give me problems as well but then I did a lot of research and like I said before I only use them now to level out the load or when weather gets rough. Most my trim is done with the motor. It is more efficient on gas to use the motor than to throw your tabs into the water stream. I think I am going to MAster MArine tomorrow to talk face to face with someone as well. The Navy had me down in Lemoore CA for the last few days so I haven't been on line fore a few. the 14x19 will be the first I try and I will test it with the wife an daughters on the boat as this is my most common load for fishing. If I were you I would try to get your rpms up by going down to a 12.75x15. I will let you know what happens once I change mine and the weather permits me to get it out.
 
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