1986 25' Century Heavy boat...Foam soaked?

[reimelss]

I have 1986 Century Mirada and it has felt heavy since i got it 3 years ago.
I have an out drive that is only 2 seasons old. I just put in a repowered 1994 Merc 350.
The RPMs at WOT were about 4k with a 13p prop on there...I have dropped sdown to an 11p and its now about 4600-4800 at wot and it seems to have more pop in the holeshot...but top end seems to be a lil slower.

With the 13p prop the boat got up on plane with out a problem with a couple people in it..actually even with 4 people in it.
But as soon as you add a 5th person and a cooler it just seems to dog.

I havent been able to test that type of load with the new 11p prop yet.

I was wondering if anyone knows about the foam in larger boats like this...everything i research on the form is for smaller boats with large decks...my boat has a cabin so im not sure where to access thee foam.
I am thinking that in the engine compartment on the left and right sides there are these compartment like platforms that my freshwater, batteries, hot water etc sit on...Is there foam under those and would i be able to access that?
Also is this something i can do on the water?
If foam does exists and is soaked can anyone weigh in on choosing to remove it and replacing it or just removing it?...noty sure how much it affects a boat that size.

Any insight would be great..please let me know if you need more details or if i am leaving anything out.

 

[oops!]

Re: 1986 25' Century Heavy boat...Foam soaked?

that boat should be running a 19 p.

11 is just crazy.

some 25's did not have foam.....but i need to see pics of the boat.
wet foam means you have real issues.

the best thing to do is find the manufacture specs of the boat....and weigh it on the scales.

foam can hold a lot of water.....

iboats restoration section is full of boat rebuilds including re foaming. but dont plan on it this season...lol....wait till the winter....it is not a day or two job.

count on a minimum of a month if you do it your self.

however....lets not jump to conclusions here....weigh the boat first.
also do a compression test on the 350....you just might need a re power. both the foam and re power will be about the same money.

 

[26aftcab454]

Re: 1986 25' Century Heavy boat...Foam soaked?

I have 1986 Century Mirada and it has felt heavy since i got it 3 years ago.
I have an out drive that is only 2 seasons old. I just put in a repowered 1994 Merc 350.
The RPMs at WOT were about 4k with a 13p prop on there...I have dropped sdown to an 11p and its now about 4600-4800 at wot and it seems to have more pop in the holeshot...but top end seems to be a lil slower.

With the 13p prop the boat got up on plane with out a problem with a couple people in it..actually even with 4 people in it.
But as soon as you add a 5th person and a cooler it just seems to dog.

I havent been able to test that type of load with the new 11p prop yet.

I was wondering if anyone knows about the foam in larger boats like this...everything i research on the form is for smaller boats with large decks...my boat has a cabin so im not sure where to access thee foam.
I am thinking that in the engine compartment on the left and right sides there are these compartment like platforms that my freshwater, batteries, hot water etc sit on...Is there foam under those and would i be able to access that?
Also is this something i can do on the water?
If foam does exists and is soaked can anyone weigh in on choosing to remove it and replacing it or just removing it?...noty sure how much it affects a boat that size.

Any insight would be great..please let me know if you need more details or if i am leaving anything out.

I do not think my 1984 Wellcraft has any flotation foam- I would be suprised if you did.They sound simular type of pocket cruisers of the same era.cept mine is repowerd in 1996 and haulz azz!

 

[reimelss]

Re: 1986 25' Century Heavy boat...Foam soaked?

that boat should be running a 19 p.

11 is just crazy.

some 25's did not have foam.....but i need to see pics of the boat.
wet foam means you have real issues.

the best thing to do is find the manufacture specs of the boat....and weigh it on the scales.

foam can hold a lot of water.....

iboats restoration section is full of boat rebuilds including re foaming. but dont plan on it this season...lol....wait till the winter....it is not a day or two job.

count on a minimum of a month if you do it your self.

however....lets not jump to conclusions here....weigh the boat first.
also do a compression test on the 350....you just might need a re power. both the foam and re power will be about the same money.

I thought the 11 was way to small...but i cant run the engine on with that low of rpm at WOT..wopnt it damage the engine?
The thing is the compression is great on all cylinders..and the boat did the same thing with the previous engine...so im not thinking that its the compression.

And unfort. I dont have access to a scale...I know the specs of the weight..its like 4600lbs w/o power

Where do you need the pictures of?

 

[reimelss]

Re: 1986 25' Century Heavy boat...Foam soaked?

I do not think my 1984 Wellcraft has any flotation foam- I would be suprised if you did.They sound simular type of pocket cruisers of the same era.cept mine is repowerd in 1996 and haulz azz!

I need mine to haul *** too!

 

[rbh]

Re: 1986 25' Century Heavy boat...Foam soaked?

I am definetly "NOT" the prop guy around here, that being said I would start with a 15x19 prop and see were that takes you.
The neighbours boat is about your size/and engine HP and that size is working for them.

 

[reimelss]

Re: 1986 25' Century Heavy boat...Foam soaked?

I am definetly "NOT" the prop guy around here, that being said I would start with a 15x19 prop and see were that takes you.
The neighbours boat is about your size/and engine HP and that size is working for them.

Wouldn't that just drop my RPMs.
isnt the rule for every 2in in p you change you go +/- 800-1000 RPMs
so by that math if i went to a 15 i would be approx. 3400 RPMs.

I had a 13p on there before i moved to an 11 and i was at about 4100 RPMs

I have a 15p i can try it but i dont think thats going to help... i like the pop the boat has with the 11p on there but the top end just seems short

 

[oops!]

Re: 1986 25' Century Heavy boat...Foam soaked?

have you weighed the boat yet?....

my 25 footer is heavy but with a 350 and an alpha im seeing 50 mph on the water.

it could be also that the gear ratio you have in the drive is wayyyy too low.

is it an alpha or a bravo?
the gear ratio is on the side of the uppers, just below the sticker.

should read 1. 5 ish to 1.8 ish.

if you are reading a 2. somthing or other the ratios are off with your repower.

 

[reimelss]

Re: 1986 25' Century Heavy boat...Foam soaked?

have you weighed the boat yet?....

my 25 footer is heavy but with a 350 and an alpha im seeing 50 mph on the water.

it could be also that the gear ratio you have in the drive is wayyyy too low.

is it an alpha or a bravo?
the gear ratio is on the side of the uppers, just below the sticker.

should read 1. 5 ish to 1.8 ish.

if you are reading a 2. somthing or other the ratios are off with your repower.

See I should be doin 50mph too! Damn that makes me so mad.

unfortunately I dont have access to a scale..

Its an Alpha 1 aftermarket ...2 years old from SEI its 1:47 ratio...i used to have 1:65 which was too high.

What year is your boat?
Does it have foam?

 

[180Fisherman]

Re: 1986 25' Century Heavy boat...Foam soaked?

If you have a 25' anything with a single 350 doing 50mph you have a freak of nature. Most would be dogs and even with 454 you'd likely see no more than high 40's. 25' is definitely getting into twin engine territory.

 

[reimelss]

Re: 1986 25' Century Heavy boat...Foam soaked?

Right now i have an Aluminum prop on there...I have a stainless thats an 18p...should i switch to that?

 

[CHAWK46]

Re: 1986 25' Century Heavy boat...Foam soaked?

Centurys were very well built boats and may weigh a little more than others the same length. That being said, my Century 210LX is 21.5 ft. with the 350 magnum and does just over 50 mph with a 14 x 19 prop.

 

[26aftcab454]

Re: 1986 25' Century Heavy boat...Foam soaked?

my 1984 Wellcraft aft cab 1996 7.4 /bravo3 tops out at 43mph-jumps on plane quick--it is 5700lb dry w/o power + i have genset+hotwater tank and a whole bunch of other "stuff".

I'm told my boat origanal power was the 350 (260HP) and would top out at 28MPH

 

[JoLin]

Re: 1986 25' Century Heavy boat...Foam soaked?

If you have a 25' anything with a single 350 doing 50mph you have a freak of nature. Most would be dogs and even with 454 you'd likely see no more than high 40's. 25' is definitely getting into twin engine territory.

Depends on the boat. 50 mph is unusual in that size, but mine will run into the mid-40's (on GPS) easily with 2 aboard and all our stuff. Dry weight of my hull is over 5200 lbs, too- it's a tank.

The 1999 Boat Test report on the same exact boat reported 50-point-something mph with 2 aboard and a half tank of fuel. Of course, it had no bottom paint or any other stuff on it.

The OP's boat is likely carbed instead of FI (lower horsepower), and he doesn't have the dual-prop drive I have. However, my friend's 1992 Larson 25 cruiser with the same setup as the OP's, will run into the mid-high 30's.