will a severely barnacled hull prevent engine from reving up to full speed?

[sdowney717]

The hull of my 37 foot boat is loaded with big barnacles which has hurt our forward speed.

I found out yesterday on the water that the engines wont rev past 2500 rpm doing a WOT test. I remember years ago they would rev slightly past 3000 rpm.
They dont miss overheat and run smoothly with good fuel. so was wondering if dirty hull has effect on engine top rpm? This past summer we dove on boat and supposedly props are clean. It really does not concern me much as I mostly operate the boat in the 1000 to 1500 rpm range.

 

[robert graham]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

I would say a definite yes...guess that's why folks spend so much money on anti-fouling paint and hull cleaning...

 

[rockyrude]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

I would also add the drag from your hitchhikers is affecting your fuel usage.

 

[rbh]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

The hull of my 37 foot boat is loaded with big barnacles which has hurt our forward speed.

I found out yesterday on the water that the engines wont rev past 2500 rpm doing a WOT test. I remember years ago they would rev slightly past 3000 rpm.
They dont miss overheat and run smoothly with good fuel. so was wondering if dirty hull has effect on engine top rpm? This past summer we dove on boat and supposedly props are clean. It really does not concern me much as I mostly operate the boat in the 1000 to 1500 rpm range.

NO, the issue with barnacles is one thing, the issue with not having the max RPM thrust to move is another.

Clean your hull!

Get a tune up!

 

[steelespike]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

No question they are causing excessive drag. There is every possibility the boat could be twice as fast at 1500 with a smooth hull.
Speed is the determining factor for best mileage. Your motor uses a given amount of fuel at a given throttle setting
regardless if your loaded with barnacles or slick as glass, but your speed will be less with the drag.It's not a stretch that you could be using twice as much fuel at certain speeds.

 

[Don S]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Clean the hull, and the rpm will come up. The prop probably looks like the hull. Spin that if you can :facepalm:

 

[tpenfield]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

anti-fouling paint would be good for you.

 

[Glowplug007]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

I'm a lake boater so no barnacles, however I did have a bunch of moss growing on the hull after a season in the slip. Couldn't have been more than 1/8in thick and it did the same thing for me. WOT gave me 3000rpm and about 20mph. Usually its 4800ish rpm and 43mph. I thought something was mechanically wrong and freaked out. 1 acid wash later and good as new!

 

[H20Rat]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Speed is the determining factor for best mileage. Your motor uses a given amount of fuel at a given throttle setting

Actually engines will use slightly LESS fuel with a dirty hull, if you are comparing WOT to WOT. Think of it in EFI terms. At WOT each injector is going to be firing X cc's of fuel. At 2500 rpm, the injectors are firing less frequently than at 3000, even though they are firing the same amount of fuel.

 

[Ned L]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

smokingcrater - I understand what you are saying, however, ... Consider a lightly loaded boat with a clean bottom, the engine will not have to work very hard to hit 3000RPM, therefore the EFI system will be injecting only the small amount of fuel needed to make the 3000 RPM. Conversely, a loaded boat with a fouled bottom, the engine will be doing everything that it can to be able to just sqeek out that 2500 RPM, the EFI system will be injecting all the fuel that it can (within the programed perameters) to try to get to the 3000 RPM. (Less injections perminute certainly yes)
------ Or am I outdated in my thinking - which is along the lines of how a traditional diesel works.

 

[robert graham]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Actually engines will use slightly LESS fuel with a dirty hull, if you are comparing WOT to WOT. Think of it in EFI terms. At WOT each injector is going to be firing X cc's of fuel. At 2500 rpm, the injectors are firing less frequently than at 3000, even though they are firing the same amount of fuel.

I've got some serious doubts about this!....

 

[Frank Acampora]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Another one for the Mythbusters!

But, I'm with Bob.

The computer is going to regulate the amount of fuel the injectors deliver based on a number of engine parameters, including THROTTLE POSITION, LOAD and RPM. EFI fuel injectors ALWAYS open fully. (This is goverened by the need to deliver a consistant spray pattern. Partially open injectors vary the spray pattern undesirably)

The amount of fuel delivered is governed by the length of time they are open. While the pulse rate may be less because of load the pulse duration may very well be longer, increasing fuel delivered.

A dirty hull has more drag and it will take longer to get where you are going. In the real world, you will use more fuel.

 

[cyclops2]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Nobody should like a dirty bottom.

I want nothing to do with a boat owner who has a dirty bottom.

 

[emoney]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

You can almost guarantee that your prop and any exposed driveshaft is also covered in barnacles. Those nasty little buggers can hold on to anything. Super glue companies would be well served to just squeeze "barnacle sticky juice" into a bottle. If they're that thick on the hull, you're also trying to turn about double the amount of weight in that prop too.

You can probably find a local diver that will clean the bottom for a fee. Around here, they're pretty reasonable usually too.

 

[sdowney717]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Oh they are thick like every square inch has a inch square barnacle about an inch high.
Do barnacles grow on top of other barnacles?
This summer we got in and scraped the hull from waterline down about 2 feet.
Took the boat close to sandy shore on the Back River near LAFB. So we were able to stand in the water and scrape.
And I noticed it improved the speed.
We could not reach any further. I used some long flat oak scrapers I made on the table saw.
We are on the third year in the water in the Chesapeake Bay.
I plan to haul in the coming spring. My slip neighbor says after we scrape to dissolve off what is left using muriatic in a spray bottle. He did this and it takes off the entire barnacle base.

How long should a bottom paint last?
Cost maybe about $600 for hauling and painting it myself.

 

[Frank Acampora]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Just be very careful with the muriatic acid. Gloves, gauntlets and a mask are mandatory for safety. The chemical name is Hydrochloric acid and it is very aggressive toward skin. The fumes will cause respiratory distress too. AND Maryland DNR may have some rules about its use in a watershed--even on dry land.

The thing about hydrochloric is that when it reacts it makes many organic compounds soluable in water (including Barnacle Bill the Sailor. Oops meant to say barnacle glue; you know the song. LOL) Thus many of your medicines are called blah-blah-blah hydrochloride. It enables you to absorb them.

 

[sdowney717]

Re: will a severely barnacled hull prevent engine from reving up to full speed?

Acids react to form salts. The whole chemical thing here is rather overblown as to the effects on land. People use it on their sidewalks and driveways and in their pools. I pretty much expect when it hits the ground after dissolving the calcium in the shells it will have lost much of its power and the ground will finish neutralizing what is left.
Yes to personal safety. I am familiar with using this product. You can buy 30 baume at the HDepot in the pool section. Definitely have a hose nearby in case you do something dumb.
We are in SE VA near LAFB on the Back River.