Engines have a sluggish feeling

3

340DA

Member
Jul 21, 2008
365
LI Sound
Boat Info
2000 Sundancer Sport Cruiser
Engines
454 Mercruiser w/Bravo III Drives
I have a 2000 340 DA with 7.4l Bravo 3s. Lately, the engines seem to "feel" sluggish. What I mean is, it seems to be taking more time, than usual, to get up on plane.
The outdrives are all the way down, trim tabs are all the way up, full water, 3/4 fuel in tank. Lately I've also been taking more people. Yesterday there were 7 onboard. (3 of them were my daughters college girlfriends so NOT a "lot" of weight there). However, I have had this many people in the past without this sluggishness feel. This boat has always had plenty of power.
The engines just seem to struggle with trying to get the boat onto a plane. Almost as if something is trying to hold me back. The engines are not misfiring or sputtering, they just seem to be lacking required power.
Yesterday, I had to adjust the weight in the boat to help. I had to move a few people from stern to mid ship to help with planing
Eventually I do get on plane but it's taking more time than usual.

(i know the marina did not change the spark plugs beginning of this season because they indicated the plugs looked fine from previous year. like I said, there is NO misfiring)

Any thoughts?
 
Might need to use a little tab. How are the wot and cruising numbers. Any change there?
 
Once I am get plane, I have to increase rpm by about 200rpm. At 25mph I am at 3400rpm, Usually I am at 3200rpm.

Regarding the hull, there is some scum around the hull. I am assuming there's scum on the bottom too. Yesterday, I jumped into the water thinking there are barnacles on the outdrives and/or tabs. But there were very few. BUT, I did notice scum..
Could scum cause that much "drag"?
 
340DA said:
Once I am get plane, I have to increase rpm by about 200rpm. At 25mph I am at 3400rpm, Usually I am at 3200rpm.

Regarding the hull, there is some scum around the hull. I am assuming there's scum on the bottom too. Yesterday, I jumped into the water thinking there are barnacles on the outdrives and/or tabs. But there were very few. BUT, I did notice scum..
Could scum cause that much "drag"?
Click to expand...

It’s possible. Depends on how thick it is.

How’s the condition of your bottom paint? Smooth, or are there areas where it’s chipped off so it’s rough?
 
Bottom paint has a few chips. I would not say it's bad though.


Regarding scum, I took a brush and was able to take some scum off the sides..... if I run the boat at crusing speed for a while, will that clean off some of the scum?
 
Running the boat will help, but don’t forget there is a very large area under the boat that you haven’t checked. This late in the season, it’s possible that you have some barnacles growing. I’ve seen them bunched up like a beehive on some.

Are you comfortable with a mask and some fins?
 
340DA said:
Bottom paint has a few chips. I would not say it's bad though.


Regarding scum, I took a brush and was able to take some scum off the sides..... if I run the boat at crusing speed for a while, will that clean off some of the scum?
Click to expand...

Just running doesn’t do much for scum. Helps a little. It once it’s on there a brush is way more effective. Even just a light brushing wit a soft brush can be very effective.

I’ve also seen clusters of barnacles on the bottom. That with soft growth could do it.

A chippy bottom can really impact your performance. I had huge gains after my bottom was stripped and repainted. Not that you necessarily need that - just some info.
 
340DA said:
I have a 2000 340 DA with 7.4l Bravo 3s. Lately, the engines seem to "feel" sluggish. What I mean is, it seems to be taking more time, than usual, to get up on plane.
The outdrives are all the way down, trim tabs are all the way up, full water, 3/4 fuel in tank. Lately I've also been taking more people. Yesterday there were 7 onboard. (3 of them were my daughters college girlfriends so NOT a "lot" of weight there). However, I have had this many people in the past without this sluggishness feel. This boat has always had plenty of power....
Click to expand...

Your post says the tabs are all the way "up". I assume you mean down, meaning set full bow down for takeoff? That, with trimming the drives in (down) will get the fastest time to plane.
 
Other than the outdrives, we have same boat... Under your port side, about 4 feet up from the stern, and in (under the boat) about 2 feet, feel for barnacles... Depending our the bottom paint you use, my paint deteriorates around the through hull fittings, especially on the port side... Barnacles will build up and give you the sluggish feeling... I was on a trip to Montauk, and had to hire a diver to scrap my bottom due to barnacles...
 
check your fuel pressure... mine started with that sluggishness before my cool fuel took a shit on me.
 
Seapig said:
Hull dirty ?
Click to expand...

That’s my first thought. Especially after the hot summer we had. If you don’t go for a good run at least once a week you’ll wind up with a dirty bottom.
 
I'm in Connecticut, middle of long island sound, about a half mile up a river. Last year we had unusual furious bottom growth. Lost about 5mph. Couldn't get close to the normal RPMs. It was struggling to get to 29mph and usually cruises at 26. scraped and did fresh bottom paint over winter and easily hit 36mph at beginning of year. Was so bad my buddy hauled his mid season.

Just throwing out a couple oddball things from my experience - I once didn't notice that the trim tab ground wire came loose so they weren't working and I don't know for how long. Those things are hard to hear.

One that seemed to help a lot - One year I had the props tuned - cost was something like $250 and whoa. Better response, better speed. Consideration if you boat around any shallow areas/mud/silt.
 
You must log in or register to reply here.

Forum statistics

Threads
113,117
Messages
1,426,459
Members
61,033
Latest member
SeaMonster8
Back
Top