Boat will not plane out with heavy load

toddh

Active Member
Jun 23, 2009
151
Southern Indiana
Boat Info
260 Sundeck
Engines
350 MAG
Hey guys, had the boat loaded up Saturday with a bunch of people and it would not get up on plane. Probably getting to 3k rpm. Sunday just the wife and I went out and it would get up on plane and get up over 3500 rpm. But I could feel the prop slipping. Any suggestions? Coupler?
 
I'm thinking one prop is spun and the other isn't and that's why it'll run fine with a light load.
 
If anything was slipping behind the engine, your rpm's would be high.
Any idea of how heavy you were when fully loaded?
 
i had a VP 5.7L with 320HP on a four winns 268 vista (weighed 6300lbs dry). when i had full fuel and 8 electricians onboard, struggled to get on plane... one of my buddies went up to the front and got enough weight to be able to get on plane....

how long have you had it? should get close to 4800 rpms at full throttle.... if the most it gets lightly loaded is 3500 or 4000, something is not right, but i don't think its slippage....
 
How many people? How many coolers, bags and other gear? I think you were overloaded for whatever drive/prop combination you have, considering you were back up on plane the next day.

If you only do that load once a year, you may be limited to cocktail speed for the day. If it’s a more regular occurrence, you’ll need to get a bigger boat or similar sized with a big block.

I had a 20’ boat once that was horribly underpowered with an in-line 4. I thought a smaller engine would be more economical, but it burned more gas and had less utility than a larger boat with a bigger engine as I had to run it at almost WOT all the time. I had to send someone forward to get on plane with more than 3 onboard. It sucked!

After that, I want a boat with the largest engine or engines that it could be purchased with. I end up running at a lower rpm, burning relatively less fuel, and being able to take all the people and gear I want (within reason).
 
Had 7 people and probably 4 coolers. I’ve done it before. It was wide open running 3000 rpm and doing probably 15 mph. Saturday with just the wife and I and it ran fine. Oil temps etc seemed fine
 
Any
i had a VP 5.7L with 320HP on a four winns 268 vista (weighed 6300lbs dry). when i had full fuel and 8 electricians onboard, struggled to get on plane... one of my buddies went up to the front and got enough weight to be able to get on plane....

how long have you had it? should get close to 4800 rpms at full throttle.... if the most it gets lightly loaded is 3500 or 4000, something is not right, but i don't think its slippage....
other suggestions?
 
7 people is alot. Both of our boats struggled with 4 or more. This boat is ok with 4 but I think even 5 it would struggle a little. with 7 i don't think there is any way ours would plane out. Doubt it would even with 6
 
Unfortunately it’ll be Sunday before I can try it again. We’ve ran 4-5 people lots of timeS with no issues planing out but I never really ran it hard. So 4500 rpm would be normal when lightly loaded? 350 mercury 24p prop
 
Unfortunately it’ll be Sunday before I can try it again. We’ve ran 4-5 people lots of timeS with no issues planing out but I never really ran it hard. So 4500 rpm would be normal when lightly loaded? 350 mercury 24p prop
Was everyone in the back? Any passengers in the bow seats?
Did you drop the trim tabs when trying to get up on plane?
 
Hey guys, had the boat loaded up Saturday with a bunch of people and it would not get up on plane. Probably getting to 3k rpm. Sunday just the wife and I went out and it would get up on plane and get up over 3500 rpm. But I could feel the prop slipping. Any suggestions? Coupler?

What boat? Bottom clean? Last tuneup?

All else is speculation.
 
Any

other suggestions?

Need to know what is the top rpm lightly loaded, to determine if your boat is running correctly. If it is, I believe your boat was overloaded for your engine. It’s not slippage, your rpm would be at red line....

If it’s not overloaded, could be as simple as bottom growth, (is this a trailered boat or slipped) need a tune up bad gas etc....
 
Boat is on a trailer and clean. Two big guys in the front, the rest were in the back. Tried trim tabs and everything else and it would not plane out. It's was went thru last spring as far as a tune-up. I'll give it a go on Sunday and see what the WOT rpm's are and report back. 260 sundeck with a 350 MAG. Big boat for that motor.
 
Assuming relatively normal size people, give or take, that boat will definitely plane with the load you mentioned. You know this, but I just wanted to give a heads up to others that aren't overly familiar with the boat. It does amazingly well with the 350MAG.

As noted above, since you have a Bravo drive, there is no hub. The coupler can do the same thing as a spun hub, but (also as mentioned) your RPM's would go up. You didn't mention that they did that. But you did mention that you could "feel the prop slipping". I'm curious what you mean by that?

With a light load - say just you onboard - you should be able to easily get 4,800RPM's - 5,000 is that engine's maximum spec. In most cases you can get that - and even a bit more.

Check fuel pressure and/or pull the fuel regulator and look - your model year is in the range of the Cool Fuel 3 "paint" issues.
 
Cool fuel issues were resolved years ago on it. I thought I felt it slip on Sunday with just me and the wife but maybe it was just my mind playing tricks on me. RPM's definitely did not go up. So I am eliminating lower unit issues. I've had a lot of people on the boat before, maybe 7 plus coolers, and it seemed fine. That was a year ago.
 

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