Boat only planes out after shifting weight forward?

[jackmorgan]

look at the numbers on the prop to see what you have. however at 4300 RPM, I would say either your down a cylinder, or your over-propped.

FWIW, my pig of a boat would hit 46mph at 4600rpm with 6 people on board (or 4 people and 4 dogs) with the 5.7 and 290DP drive running B6 props, a full fuel tank, and 40# of ice and 6 cases of beer. hole-shot was about 50' long to be up and on plane. the B5 props would have a greater hole shot, however I had a lower top end.

they're F4 so that's not the issue

 

[jackmorgan]

Agree 100% with everything in this statement.

good to know. all the more reason to want 100% of available power.

 

[jackmorgan]

Maybe you're not achieving WOT? Linkage adjustment?

checked that a while back - it's ok.

 

[rallyart]

Sadly, you now know why the previous owner sold the boat. So, you have good compression readings on a low hour engine. Assuming it is in good tune it has what power it is going to have and you have a problem to fix. Re-powering is an expensive fix but should remedy the problem. Much cheaper, but not cheap, is to put on a lower pitch prop set. The engine needs to be in a higher rpm range to get you out of the hole and you are no where near the optimum range for the engine at full power. Who cares if it is the stock prop. If the engine is running correctly it is not the right one for the boat, stock or not. I think this will be essential.

Moving weight forward stops you from pushing as much water aside and allows the boat to come out faster. Maybe look at moving weight permanently forward. You may need more lift on the stern so longer trim tabs or a foil might help. Full throttle and trimmed in until fully on plane is essential when a boat has problems like yours. Finding a fix can cost lots of money but you may find patches that limit the problem. That's like moving people weight forward, adding a foil, or moving weight forward permanently.

 

[bruceb58]

I was actually looking at this model boat many years back. What turned me off on it was the small engine they put in it. When I met someone that had one at the lake and he told me that he ran it at 4500 RPM all the time, I decided not to bother. Apparently, no BBC was ever offered in this model which surprised me.

 

[jackmorgan]

Sadly, you now know why the previous owner sold the boat. So, you have good compression readings on a low hour engine. Assuming it is in good tune it has what power it is going to have and you have a problem to fix. Re-powering is an expensive fix but should remedy the problem. Much cheaper, but not cheap, is to put on a lower pitch prop set. The engine needs to be in a higher rpm range to get you out of the hole and you are no where near the optimum range for the engine at full power. Who cares if it is the stock prop. If the engine is running correctly it is not the right one for the boat, stock or not. I think this will be essential.

Moving weight forward stops you from pushing as much water aside and allows the boat to come out faster. Maybe look at moving weight permanently forward. You may need more lift on the stern so longer trim tabs or a foil might help. Full throttle and trimmed in until fully on plane is essential when a boat has problems like yours. Finding a fix can cost lots of money but you may find patches that limit the problem. That's like moving people weight forward, adding a foil, or moving weight forward permanently.

I see what you're saying, but i still think i'm missing some power - other owners of the same boat say they max out at 4800rpm. Boat test said the same - with the f4 prop and similar load. I have new plugs and wires on order and if i don't notice any difference i may get the injectors bench cleaned. Will report back.

 

[jackmorgan]

I was actually looking at this model boat many years back. What turned me off on it was the small engine they put in it. When I met someone that had one at the lake and he told me that he ran it at 4500 RPM all the time, I decided not to bother. Apparently, no BBC was ever offered in this model which surprised me.

With the 5.7 I have you can cruise at 3100rpm at 30mph and get 2.2MPG which isn't too bad. With the 5.0 you will need 4500rpm for best fuel economy (way too high of an rpm to be running at i agree) and 35mph - that's probably the engine the guy had.

 

[redneck joe]

Waterlogged?

.....

 

[jackmorgan]

.....

what do you mean by waterlogged? the fiberglass? the bilge is clear.

 

[redneck joe]

Sorry sir missed on your first post you are new to boating. I'm assuming is has flotation foam below decks. If left outside and not protected properly for even a season or two the water can soak up in the foam. An 07 boat is now ten years old.

Search the terms 'water logged' and 'foam' here on the forum and you will find more than a few threads.

There are many smarter people on here than me but in a 25' boat you might could have an extra 500-800 lbs of extra weight many times in the rear of the boat. Under the deck. Get your boat weighed - it is new enough you should be able to get specs to do without too much trouble.

Could be just underpowered motor or you have a engine performance issue but heavy foam can exacerbate that.

 

[bruceb58]

With the 5.7 I have you can cruise at 3100rpm at 30mph and get 2.2MPG which isn't too bad.

Are you positive you have an F4 prop and your tach is correct? Assuming you have a 1.95 gear ratio drive, there is no way you are going 30MPH at 3100RPM.

The guy had a 5.7L in it.

According to my prop chart, F4 with a 1.95 will be going 36 MPH @ 4200 RPM

Also, I would be VERY surprised if your hull has any foam flotation in it.

 

[jackmorgan]

Are you positive you have an F4 prop and your tach is correct? Assuming you have a 1.95 gear ratio drive, there is no way you are going 30MPH at 3100RPM.

The guy had a 5.7L in it.

According to my prop chart, F4 with a 1.95 will be going 36 MPH @ 4200 RPM

Also, I would be VERY surprised if your hull has any foam flotation in it.

I tried to edit my response - should have been 23mph at 3100RPM. I hit 42mph at 4300 (at which point the tach won't go any higher). Definitely F4's - jumped in with a snorkel on to check. I guess the tach could be off a bit though?

I don't think there's any foam either - nothing under the cabin floor or in the engine bay that I can see.

 

[jackmorgan]

Sorry sir missed on your first post you are new to boating. I'm assuming is has flotation foam below decks. If left outside and not protected properly for even a season or two the water can soak up in the foam. An 07 boat is now ten years old.

Search the terms 'water logged' and 'foam' here on the forum and you will find more than a few threads.

There are many smarter people on here than me but in a 25' boat you might could have an extra 500-800 lbs of extra weight many times in the rear of the boat. Under the deck. Get your boat weighed - it is new enough you should be able to get specs to do without too much trouble.

Could be just underpowered motor or you have a engine performance issue but heavy foam can exacerbate that.

No problem. I understand what you're saying now - pretty sure i don't have any foam though. Checked under the cabin floor and in the engine bay - everything is fiberglass.

 

[bruceb58]

I tried to edit my response - should have been 23mph at 3100RPM. I hit 42mph at 4300 (at which point the tach won't go any higher).

That is not possible either. You need to bring along a shop tach.

 

[redneck joe]

No problem. I understand what you're saying now - pretty sure i don't have any foam though. Checked under the cabin floor and in the engine bay - everything is fiberglass.

yeah jsut did some searching and it looks like over 20' not reuired so I'm sure they did not go to the expense. For some reason I thought the threshold was 28'.

 

[bruceb58]

yeah jsut did some searching and it looks like over 20' not reuired so I'm sure they did not go to the expense. For some reason I thought the threshold was 28'.

None of the boats I have owned that are over 20' have had foam in them. Does your Carver?

 

[jackmorgan]

That is not possible either. You need to bring along a shop tach.

Here's the performance figures from boattest for the same engine and almost identical boat:

3000rpm 23.3mph
4800rpm 41.5mph

Now that i think about it I may have been going slower at WOT at 4300rpm - My dash gps is in kph and my phone is in mph. I think i was going by my phone (with navionics) so that may be off a bit. The cruise seems pretty dead on according to these numbers and my idle is perfect at 600. I tried to post the performance graph but it wouldn't upload.

 

[bruceb58]

Here's the performance figures from boattest for the same engine and almost identical boat:

3000rpm 23.3mph
4800rpm 41.5mph

Those sound correct. 42 at 4300 does not sound correct. I think your RPMs are higher than you think they are. Check with a shop tach.

What boat is Boattest running? Hopefully, a FourWinns Vista.

At this point, you just need to move weight around and correctly use your trim tabs. Your props are in perfect condition hopefully.

 

[redneck joe]

None of the boats I have owned that are over 20' have had foam in them. Does your Carver?

No sir but i thought that was due to being old.

 

[jackmorgan]

Those sound correct. 42 at 4300 does not sound correct. I think your RPMs are higher than you think they are. Check with a shop tach.

What boat is Boattest running? Hopefully, a FourWinns Vista.

At this point, you just need to move weight around and correctly use your trim tabs. Your props are in perfect condition hopefully.

Yes, it's a 2004 vista 268. I will try a shop tach and see what i get. Props are mint. Thanks for the help.