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Author Topic:   13' 1966 Whaler w/1982 35 HP Evinrude

The Mexican posted 07-12-2001 07:07 PM ET (US)
I have a technical question about my prop. I was out on Fishers Island Sound yesterday and I determined by GPS that I was cruisin at 25 knots in my whaler with one other person on board. I weigh about 275# and my buddy weighs ~250. Is that a decent speed or should I be going faster. It was slack tide and there was not much wind to speak of. The prop size is 10" diameter but I do not know the pitch. Any thoughts please chime in!! Thanks
Peter posted 07-12-2001 08:44 PM ET (US)
If the prop diameter is 10 then the pitch is 13. If the prop diameter is 10.5 then the pitch is 11. 25 knots is probably about right for the motor, boat and load.
Bigshot posted 07-12-2001 09:15 PM ET (US)
Had a 10x15 on my same setup. Was too big with 2 people. The 10x13 is perefect.
Dr T posted 07-17-2001 12:57 PM ET (US)
Great question. I was about to ask it.
I have the same motor on a 1982 13ft Sport. I currently have an aluminum 11" 9 pitch prop and use it on lakes up here in Colorado. I am using the middle hole for trim. As for perfomance, at lakes up in the mountains (~8000 ft) with myself, my daughter, and two tanks of fuel on board, I can get about 20 MPH tops. I am about your size, and the girl is about 115 lbs. I get about the same speed with my brother-in-law (wt. about 180) on board.
With 3 average sized people and me, we can get about 16 mph.
Clearly, the pitch will effect the top end, but the weight is a big factor as well.
I used the boat with a 10 x 13 stainless steel prop in Texas. I was not able to measure speed there, but it seemed to be a bit faster. However, the engine spins up much more quickly with the aluminum prop and will also plane much more quickly. I think the increase in acceleration is due both the the pitch and the weight of the prop (the aluminum prop weighs about half as much.
Does anyone have any experience with a 40 hp motor with power trim for comparison?
Bigshot posted 07-17-2001 02:19 PM ET (US)
Do you have a tach? My 10x15 would redline around 5300. The 13 about 5500(max)so it was perfect. This will only work for you if you have the old 35 2cyl OMC. If your is a 40hp or a 35 merc, etc the gear ratios are all different and an 11" might be perfect. Everyone needs a tach to properly set up a boat.
Bigshot posted 07-17-2001 02:21 PM ET (US)
a 13' sport with a 35 should run 30-35 depending on condition, etc. 20 is way too slow. Is this GPS or a speedo? Those speedos are not worth their weight in dirt under 30mph.
Dr T posted 07-17-2001 03:47 PM ET (US)
I am using a speedo with no tach. I will try to get a reading with a GPS in the near future.
It is the old 2 cyl. OMC 35 HP. The problem that I am getting into is the altitude.
In examining another thread in the forum, performance with a new 40 HP 4 cycle was about mid-30s at sea level. It had declined to mid-20s at 7000 ft. with an 11 pitch prop.
The altitude is dramatically cutting the available horsepower. It is probably only making about 20 horsepower (or less) up here.
At the altitudes we have here, it is hard to get it up on the step with a heavy stainless steel 13 pitch prop. The 9 pitch prop gets it up fairly quickly. You just don't go very fast.
At sea level, I expect it would be an entirely different matter. The power output would be much higher and expect that the 13 pitch prop would push it a lot faster and the performance would not fall off that quickly with the weight. Since The Mexican is getting aobut 25 Kn. at sea level, 20 mph does not seem that unreasonable given the factors involved.
I have not yet played around much with the trim, for example. And I am carrying an extra 60 lbs of fuel.
Bigshot posted 07-17-2001 04:12 PM ET (US)
Was it rejetted? I would figure that mixture would foul the hell out of your plugs. EFI will cure all that and go for a 50hp. That 35 really only puts out 28-30hp at sea level compared to new.
WHALERROB posted 07-17-2001 04:43 PM ET (US)
I HAVE A 1967 13 WITH A 2002 25 HP MERC 2 STROKE. NO CONFIRMED GPS SPEED AS OF YET BUT SEAT OF PANTS GUESS WOULD BE ABOUT 30 MPH WITH LIGHT LOAD. I WILL CONFIRM WITH GPS IN NEAR FUTURE.
Dr T posted 07-18-2001 01:06 AM ET (US)
No rejet. It was re-timed for the altitude, however.
An EFI 4 stroke is tempting, but it is a bunch of money to replace something that is working.
Bigshot posted 07-18-2001 09:57 AM ET (US)
have it re-jetted, makes a big dif. But will run like crap at lower altitiudes.
Dr T posted 07-31-2001 11:02 AM ET (US)
I looked up the jet specs in the aftermarket spec manual, and got the impression that it is not a big deal to do. HOWEVER, I am a rookie with carbs and the manual fails to tell you how to do it.
Now for the Rookie Question: Exactly how do you rejet the carbs?
Thanks.
Bigshot posted 07-31-2001 02:17 PM ET (US)
Have it done. Easy with the right equipment. Some drilling is usually required. With just 1 carb, worth the couple bucks.
Dr T posted 09-17-2001 01:38 AM ET (US)
After having carefully reviewed the threads on Doel Fins, Tachometers, and Performance in general over the last two months, I exchanged the generic tail cavitation plate extender for a Doel Fin. The genaric had about twice the surface area of the Doel Fin. The tail was made of a plastic similar to starboard, was 3/8" thick, and had a radiused edge (about 1/2" radius). I ended up cutting the tail up and making a new dashboard for the tach out of it. Probably the best use for the material.

Today, I measured baseline performance with the 11x9 prop, This was done runnig solo with about 8 gallons of fuel on board. The measured performance was: 24 mph indicated on the speedo at 5800 RPM. From 0 to plane in about 4.5 sec.
Next time I go out, I will use the 10.5 x 11 prop to see what happens.
Bigshot posted 09-17-2001 12:06 PM ET (US)
your redline is 5500 on that, an 11" or even a 13" is gonna be fine.
Dr T posted 09-17-2001 03:56 PM ET (US)
Nick,
Thanks, I was wondering about the redline. It looks like the 11x9 is going to be used for pulling the kids on a tube and for high in the mountains.
It will be interesting to see how the 10.5x11 and 10x13 work.
I wonder how far off my speedo is.
Terry

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Author	Topic: 13' 1966 Whaler w/1982 35 HP Evinrude
The Mexican	posted 07-12-2001 07:07 PM ET (US) I have a technical question about my prop. I was out on Fishers Island Sound yesterday and I determined by GPS that I was cruisin at 25 knots in my whaler with one other person on board. I weigh about 275# and my buddy weighs ~250. Is that a decent speed or should I be going faster. It was slack tide and there was not much wind to speak of. The prop size is 10" diameter but I do not know the pitch. Any thoughts please chime in!! Thanks
Peter	posted 07-12-2001 08:44 PM ET (US) If the prop diameter is 10 then the pitch is 13. If the prop diameter is 10.5 then the pitch is 11. 25 knots is probably about right for the motor, boat and load.
Bigshot	posted 07-12-2001 09:15 PM ET (US) Had a 10x15 on my same setup. Was too big with 2 people. The 10x13 is perefect.
Dr T	posted 07-17-2001 12:57 PM ET (US) Great question. I was about to ask it. I have the same motor on a 1982 13ft Sport. I currently have an aluminum 11" 9 pitch prop and use it on lakes up here in Colorado. I am using the middle hole for trim. As for perfomance, at lakes up in the mountains (~8000 ft) with myself, my daughter, and two tanks of fuel on board, I can get about 20 MPH tops. I am about your size, and the girl is about 115 lbs. I get about the same speed with my brother-in-law (wt. about 180) on board. With 3 average sized people and me, we can get about 16 mph. Clearly, the pitch will effect the top end, but the weight is a big factor as well. I used the boat with a 10 x 13 stainless steel prop in Texas. I was not able to measure speed there, but it seemed to be a bit faster. However, the engine spins up much more quickly with the aluminum prop and will also plane much more quickly. I think the increase in acceleration is due both the the pitch and the weight of the prop (the aluminum prop weighs about half as much. Does anyone have any experience with a 40 hp motor with power trim for comparison?
Bigshot	posted 07-17-2001 02:19 PM ET (US) Do you have a tach? My 10x15 would redline around 5300. The 13 about 5500(max)so it was perfect. This will only work for you if you have the old 35 2cyl OMC. If your is a 40hp or a 35 merc, etc the gear ratios are all different and an 11" might be perfect. Everyone needs a tach to properly set up a boat.
Bigshot	posted 07-17-2001 02:21 PM ET (US) a 13' sport with a 35 should run 30-35 depending on condition, etc. 20 is way too slow. Is this GPS or a speedo? Those speedos are not worth their weight in dirt under 30mph.
Dr T	posted 07-17-2001 03:47 PM ET (US) I am using a speedo with no tach. I will try to get a reading with a GPS in the near future. It is the old 2 cyl. OMC 35 HP. The problem that I am getting into is the altitude. In examining another thread in the forum, performance with a new 40 HP 4 cycle was about mid-30s at sea level. It had declined to mid-20s at 7000 ft. with an 11 pitch prop. The altitude is dramatically cutting the available horsepower. It is probably only making about 20 horsepower (or less) up here. At the altitudes we have here, it is hard to get it up on the step with a heavy stainless steel 13 pitch prop. The 9 pitch prop gets it up fairly quickly. You just don't go very fast. At sea level, I expect it would be an entirely different matter. The power output would be much higher and expect that the 13 pitch prop would push it a lot faster and the performance would not fall off that quickly with the weight. Since The Mexican is getting aobut 25 Kn. at sea level, 20 mph does not seem that unreasonable given the factors involved. I have not yet played around much with the trim, for example. And I am carrying an extra 60 lbs of fuel.
Bigshot	posted 07-17-2001 04:12 PM ET (US) Was it rejetted? I would figure that mixture would foul the hell out of your plugs. EFI will cure all that and go for a 50hp. That 35 really only puts out 28-30hp at sea level compared to new.
WHALERROB	posted 07-17-2001 04:43 PM ET (US) I HAVE A 1967 13 WITH A 2002 25 HP MERC 2 STROKE. NO CONFIRMED GPS SPEED AS OF YET BUT SEAT OF PANTS GUESS WOULD BE ABOUT 30 MPH WITH LIGHT LOAD. I WILL CONFIRM WITH GPS IN NEAR FUTURE.
Dr T	posted 07-18-2001 01:06 AM ET (US) No rejet. It was re-timed for the altitude, however. An EFI 4 stroke is tempting, but it is a bunch of money to replace something that is working.
Bigshot	posted 07-18-2001 09:57 AM ET (US) have it re-jetted, makes a big dif. But will run like crap at lower altitiudes.
Dr T	posted 07-31-2001 11:02 AM ET (US) I looked up the jet specs in the aftermarket spec manual, and got the impression that it is not a big deal to do. HOWEVER, I am a rookie with carbs and the manual fails to tell you how to do it. Now for the Rookie Question: Exactly how do you rejet the carbs? Thanks.
Bigshot	posted 07-31-2001 02:17 PM ET (US) Have it done. Easy with the right equipment. Some drilling is usually required. With just 1 carb, worth the couple bucks.
Dr T	posted 09-17-2001 01:38 AM ET (US) After having carefully reviewed the threads on Doel Fins, Tachometers, and Performance in general over the last two months, I exchanged the generic tail cavitation plate extender for a Doel Fin. The genaric had about twice the surface area of the Doel Fin. The tail was made of a plastic similar to starboard, was 3/8" thick, and had a radiused edge (about 1/2" radius). I ended up cutting the tail up and making a new dashboard for the tach out of it. Probably the best use for the material. Today, I measured baseline performance with the 11x9 prop, This was done runnig solo with about 8 gallons of fuel on board. The measured performance was: 24 mph indicated on the speedo at 5800 RPM. From 0 to plane in about 4.5 sec. Next time I go out, I will use the 10.5 x 11 prop to see what happens.
Bigshot	posted 09-17-2001 12:06 PM ET (US) your redline is 5500 on that, an 11" or even a 13" is gonna be fine.
Dr T	posted 09-17-2001 03:56 PM ET (US) Nick, Thanks, I was wondering about the redline. It looks like the 11x9 is going to be used for pulling the kids on a tube and for high in the mountains. It will be interesting to see how the 10.5x11 and 10x13 work. I wonder how far off my speedo is. Terry