Extra weight in boat effecting speed.

[bocco]

I had no idea how much extra weight would slow my boat down. Normally it's just me, the wife and the small dog. I run about 77mph at 4800rpms with 28 signature prop. We went to take three guys for a ride. I think two of the guys were in the 275 lb range and a skinny teenager that maybe 150. The best I could do was 66 at about 4000rpms. I couldn't hit 70 to save my soul.

 

[Flying_Lavey]

Is your boat open bow? a couple hundred pounds in the bow can make a HUGE difference.

 

[bocco]

Is your boat open bow? a couple hundred pounds in the bow can make a HUGE difference.

No. It's a closed bow DCB 24 Extreme. All three guys were in the back seat.

 

[OldSchoolBoats]

Yeah, absolutely weight can affect speed......

 

[Crazyhippy]

100lbs is a MPH with a v-bottom whacker.

 

[dribble]

OK I'll say it. Have you tried a different prop?

 

[old rigger]

100lbs is a MPH with a v-bottom whacker.

I was just going to post the same thing but when I was taught that it was back in the 70s and told to me by the guys that raced outboards then. Don’t know if it applies today with the killer OBs available? Not to mention the bigger boats.

 

[RiverDave]

I had no idea how much extra weight would slow my boat down. Normally it's just me, the wife and the small dog. I run about 77mph at 4800rpms with 28 signature prop. We went to take three guys for a ride. I think two of the guys were in the 275 lb range and a skinny teenager that maybe 150. The best I could do was 66 at about 4000rpms. I couldn't hit 70 to save my soul.

It should slow it down some, but 8 mph? You sure something else isn’t going on there?

I have seen guys pics up 3 mph just by emptying all the shit out of their boats.. lol. Ezup spawn chairs, skis, etc.. you can add a couple hundred pounds in the bow pretty quickly

 

[Crazyhippy]

It should slow it down some, but 8 mph? You sure something else isn’t going on there?

I have seen guys pics up 3 mph just by emptying all the shit out of their boats.. lol. Ezup spawn chairs, skis, etc.. you can add a couple hundred pounds in the bow pretty quickly

Only 4k rpm, motor never got into the powerband.

 

[Crazyhippy]

I was just going to post the same thing but when I was taught that it was back in the 70s and told to me by the guys that raced outboards then. Don’t know if it applies today with the killer OBs available? Not to mention the bigger boats.

Was super accurate with the 2.5's, less so with the 3.2l Optimax's, and less so again with the V-8's... But the V-8's are fast enough that we aren't running them as close to the edge (yet).

 

[NicPaus]

In my boat I have to prop down to even get on plane with 12 people. Goes from 70 to 55mph boat real quick.

 

[Uncle Dave]

Weight (people, stuff, fuel), air temps, altitude - all effect speed.

 

[FreeBird236]

I might lose 1-2mph with 600 lbs of people unless they're in the front. I can feel the difference in acceleration, but not much on top speed. Like was already stated, not in the power band, I'd say the prop is too big, Even the 4800 @ 77 the rpms are a little low. also the heat.

 

[beaverretriever]

Man, if this was 1984 you could put a sticker on it that says "No Fat Chicks". Usually adds about three to five mph.

 

[spectras only]

Most boats, especially non stepped hulls would run vetter, loaded up with people/extra gear, full tank. It becomes an uphill battle. 4800 rpm is low, especially if the rev limiter is set at 5100 or higher, need to have lower pitch prop, like a 26P

 

[Ballyhoo]

OK I'll say it. Have you tried a different prop?

That does seem like a big prop

 

[farmo83]

Long time family friend would take everything out of the boat when he was going to race someone. Even the back seat. It was quite comical

 

[fishing fool]

According to your numbers with the boat unloaded you have a 15% prop slip.... load 22% By going to a 26 prop (15 slip) speed is 71mph

I say try a different prop

I had no idea how much extra weight would slow my boat down. Normally it's just me, the wife and the small dog. I run about 77mph at 4800rpms with 28 signature prop. We went to take three guys for a ride. I think two of the guys were in the 275 lb range and a skinny teenager that maybe 150. The best I could do was 66 at about 4000rpms. I couldn't hit 70 to save my soul.

 

[bocco]

I might lose 1-2mph with 600 lbs of people unless they're in the front. I can feel the difference in acceleration, but not much on top speed. Like was already stated, not in the power band, I'd say the prop is too big, Even the 4800 @ 77 the rpms are a little low. also the heat.

The prop is a little big and I would have probably done better with my 26. In general I have never gotten the boat past 77 with either prop so I like doing it at lower RPMs and it was 109 degrees last Friday.

 

[bocco]

According to your numbers with the boat unloaded you have a 15% prop slip.... load 22% By going to a 26 prop (15 slip) speed is 71mph

I say try a different prop

Forgot to mention 1.5 gears. Below is what I get with just me and the wife. I'm OK with this.

 

[fishing fool]

Sorry, I put in 5100rpm to get the numbers I posted

Forgot to mention 1.5 gears. Below is what I get with just me and the wife. I'm OK with this.

View attachment 895164

 

[bocco]

Sorry, I put in 5100rpm to get the numbers I posted

That is what my stock rev limiter is set to. But I never get there with this prop.

 

[rivermobster]

I had no idea how much extra weight would slow my boat down. Normally it's just me, the wife and the small dog. I run about 77mph at 4800rpms with 28 signature prop. We went to take three guys for a ride. I think two of the guys were in the 275 lb range and a skinny teenager that maybe 150. The best I could do was 66 at about 4000rpms. I couldn't hit 70 to save my soul.

The Stoker hull is VERY susceptible to weight changes. Even a full tank of gas makes a big difference. In pretty much any mode of transportation, the power to weight ratio is key.

A 28 is a big prop though...