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Old 09 December 2018, 19:33   #1
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MY Top Speed Is Not So Great, Bombard C4 With 50hp

Bombard C4 with 50 hp Tohatsu

33 mph/53 km/h at 5800 rpm with just me on board.

I was hoping for at least 40 mph/64 km/h

I have it set up with jockey seat, and a hydrofoil and a Hydraulic transom plate for swallow water use.

I am running with 15 pitch prop at 5800 RPM's.

Is this normal, it does handle good, bow stays down and it plans in 1 to 2 seconds.


I have adjusted the trim and motor height and my top speed is still 33 mph/53 km/h.
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Old 09 December 2018, 20:18   #2
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I do understand the some Zodiacs have speed tubes and that lifts the boat out of water and helps with a faster speed but I at least thought a 50 hp on a Bombard C4 would be faster than 33 mph/53 km/h

Or is this about normal..
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Old 10 December 2018, 04:50   #3
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Any videos of it going along? and any pictures of the prop?
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Old 10 December 2018, 11:41   #4
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Hydrofoils reduce speed due to drag.

Videos would be helpful, especially ones showing your wake.
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Old 10 December 2018, 13:51   #5
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Quote:
Originally Posted by office888 View Post
Hydrofoils reduce speed due to drag.

Videos would be helpful, especially ones showing your wake.
When I was putting the boat together I installed the hydro foil before the 1st time using the boat so I don't know what speed might have been lost, I have heard from others its only 1 to 2 mph but many have said no mph lost, I have a auto jack plate so when running I can raise motor to get the hydro foil out of water just before the prop sucks air and it does increase my speed but that would also be the same without a hydro foil, the hydro foil pops the boat on plane at very slow speed and keeps it there so I cant see much mph lost from that, maybe when the weather here warms up I will get a video but not sure why this would help.


Would like to hear from others with similar boat and 50hp what is your top speed.
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Old 10 December 2018, 14:12   #6
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Its the fabric hull I presume. It just isn't as slick on the water. I have a Zodiac Futura MK2 with a Etec 60hp. Yea, I know its a 40hp recommend and a 50 max but the 60 was the same engine with 60hp software and was only $300 bucks more, so who wouldn't.
I have two seats mounted to low storage box with homemade stainless tube control mounting. With just me on board I only hit 37mph. 35mph with my buddy with me. Now I get to full speed in just 4 sec but the engine runs at 6000. I debate getting a stainless prop with hopes of dropping revs to 5900 and add a couple mph but I would need to find the prop used so when I find out it didn't help I can flip it with little financial pain.
My Zodiac dealer told me to increase the tube pressure 1/2 a psi. So go from 3.4 to 4psi. He guessed I could get 5 mph more but that sounds like what a prop salesman would promise you to make a sale. Ill try that first but where I boat there is a big temperature change during the day so checking on the pressure is a hassle but a must do when you over pressure.
My prop is a 13.3 17P 3blade - a pull toy prop is a 13" 15P 4 blade. it goes 33mph with two on board and jumps out of the water when you hit it.
The boat is extreamly stable with no sketchiness with the 60HP.
I love my boat
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Old 10 December 2018, 14:37   #7
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Quote:
Originally Posted by pagick View Post
Its the fabric hull I presume. It just isn't as slick on the water. I have a Zodiac Futura MK2 with a Etec 60hp. Yea, I know its a 40hp recommend and a 50 max but the 60 was the same engine with 60hp software and was only $300 bucks more, so who wouldn't.
I have two seats mounted to low storage box with homemade stainless tube control mounting. With just me on board I only hit 37mph. 35mph with my buddy with me. Now I get to full speed in just 4 sec but the engine runs at 6000. I debate getting a stainless prop with hopes of dropping revs to 5900 and add a couple mph but I would need to find the prop used so when I find out it didn't help I can flip it with little financial pain.
My Zodiac dealer told me to increase the tube pressure 1/2 a psi. So go from 3.4 to 4psi. He guessed I could get 5 mph more but that sounds like what a prop salesman would promise you to make a sale. Ill try that first but where I boat there is a big temperature change during the day so checking on the pressure is a hassle but a must do when you over pressure.
My prop is a 13.3 17P 3blade - a pull toy prop is a 13" 15P 4 blade. it goes 33mph with two on board and jumps out of the water when you hit it.
The boat is extreamly stable with no sketchiness with the 60HP.
I love my boat
Well than I guess I my speed is normal than, on the North American thread they have post of people top speed and some with 150 hp don't see much above 50 mph so I guess mine is normal, it does perform very well and does not have any bow rise issues at top speed, when it warms up wee need to meet in Lake Havasu
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Old 10 December 2018, 14:45   #8
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The bigger Hp can't seem to break the 40 mph but it can really help when you add the 4-5 guy to the boat.
Ill post some videos and a pic of my setup once I upload to youtube
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Old 10 December 2018, 15:30   #9
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I would suggest a higher pitch, like 19 or 21 to increase speed.
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Old 10 December 2018, 16:02   #10
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I wouldn't change prop pitch as the one you are currently using already gets you into the max rpm range with just one person onboard. A larger pitch will reduce your max rpm and put more strain upon the engine, especially if you load the boat with more than just yourself.

Personaly I've never liked using any kind of foil on outboards, partly as they wave your warranty rights on new outboards over this side of the pond. I've also had some diverse dangerous experiences using them in very rough weather on standard mono hulls.

Prop shape can make some difference as can extra cupping of the blades. Engine mounting height can also effect speed but I doubt you will reach that 40mph from simply raising one or two holes but you will gain speed.
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Old 10 December 2018, 16:50   #11
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Quote:
Originally Posted by DiabloLoco View Post
I would suggest a higher pitch, like 19 or 21 to increase speed.

That would be to much prop for my boat/motor set up, I have both 14 and 15 pitch prop, the 15 pitch has me at 33 mph at 5700 to 5800 rpm, the 14 pitch has my rpm's at 6100 but the boat takes off fast with the 14.

16 pitch would be my max if I ever wanted to try it but that would lug my motor.
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Old 10 December 2018, 17:02   #12
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Quote:
Originally Posted by jonp View Post
I wouldn't change prop pitch as the one you are currently using already gets you into the max rpm range with just one person onboard. A larger pitch will reduce your max rpm and put more strain upon the engine, especially if you load the boat with more than just yourself.

Personaly I've never liked using any kind of foil on outboards, partly as they wave your warranty rights on new outboards over this side of the pond. I've also had some diverse dangerous experiences using them in very rough weather on standard mono hulls.

Prop shape can make some difference as can extra cupping of the blades. Engine mounting height can also effect speed but I doubt you will reach that 40mph from simply raising one or two holes but you will gain speed.
I have a hydraulic transom plate and can adjust my motor height up to 5 inch's on the go, I can take it so high I lose prop grab at high speed than bring it down to maintain my 33 mph..


As reading other post on here and on other threads it appears I am at what my boat/motor combo will do with the Bombard C4, I am not disappointed with my speed just thought it would have been faster.

However I can go into very shallow waters and that I like, the hydro foil lifts my back out of the water at very slow speed and with the hydraulic transom plate I set my motor height up high and I can run in 12 inch's of water safely.
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Old 10 December 2018, 17:12   #13
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I also added a 2nd layer of PVC on the bottom of my boat for the swallow water use and beaching the boat, I don't think it slowed my speed down but I don't have to worry much about rocks and such now.
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Old 10 December 2018, 21:18   #14
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Here are some SIB videos I posted on youtube. Showing speed with two different motors.
My boat was first setup with a 40HP 4 stroke but the performance was sluggish from what I wanted. It felt stuck to the water.
Over winter I sold the 40 and ordered a 60hp ETEC 2 stroke.
The 40 would push the boat at 30 mph, the 60 only bumped it 7 mph to 37 but it feels like its flying now. Far faster than what you would think a 7 mph should feel like. Its very stable!
Pics and videos below.

This video is the 40hp at 30mph. https://youtu.be/tOutzKXC9f0

This video shows the 60hp going 37mph in light chop. Parker Strip, AZ. https://youtu.be/0As0I1KM0tQ

On glass heading up river to Topic Gorge Lake Havasu, AZ. https://youtu.be/iVxUxJNQgIc

End of day heading back to the London Bridge! The very you you UK guys sold us. We put it in the desert!
https://youtu.be/gqOr18CK1cg
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Old 11 December 2018, 00:05   #15
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That's a nice boat pagick, I was thinking of going with a larger HP motor but was a little worried about the extra weight on transom, I have a 2018 Tohatsu 4 stroke 50hp, it is the lightest in its class and has 15 inch shaft for the Bombard C4, weights only 209 lbs plus the 23 lbs for the hydraulic transom plate = 232 lbs on a transom rated for 235 lbs, I did add supports to my transom to make sure bouncing on waves don't do damage.

I was looking at the Evinrude's but they sure were pricey but hear they are great motors.

So far I am happy with the Tohatsu, its has some good grunt and takes off really fast.
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Old 11 December 2018, 11:24   #16
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With the ETEC evenrude the 40,50 & 60 all are 60 hp with different software to reduce the lower hp units. My zodiac dealer said the boat can handle it and I should get 40 mph. Boat insurance wasn’t a problem either.
When I got my ETEC, Evenrude offered a free extended warranty. 10 years. First service is at 300 hr or 3 years. Weight is 247# just under the max engine weight. I saved almost $2000 getting it from Wisconsin.
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Old 22 December 2018, 17:34   #17
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Hey pagick I was wondering if your top speed is hurting cause you have the canopy up, when I had a pontoon boat even though it was slow it would loose about 2 to 3 mph with the canopy open vs being closed.
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Old 22 December 2018, 19:29   #18
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PCanopy did not make much difference. At most 1 mph lower.
I have been talking to some guys about props and my rpm. One prop was recommended that is said to possibly get me 3-4 mph more. I bought it used so if it doesn’t help I can flip it. It’s a semi cleaver in stainless designed by evenrude 19p. My prop now is 17 chopper in alu. I am also planning on over pressuring the tubes a1/2 psi. That is said to get me a few mph more too. According to my zodiac dealer. So if both guys are half right I can hit the magic 40 mph
Also my speed stated is in 110-120f degree air. That is slower. I went to same waterway when it was 85deg and I got another 1.5 mph out of the boat.
Too bad there isn’t an anti-wetting agent you can put on the bottom to make it more slick on the water at speed.
I’m looking forward to boating with you this summer on lake havasu especially since our boats have similar setups. And for once I’m not the only sib on the lake.
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