7.4 l mercuriser 2000 arc Maxum

[Bobportante]

Hey all, I’m having an issue I’m hoping i can get some help. I have a 2000 Maxum scr2800 with a single 7.4 mercruiser. The boat was running fine on my way out to the bay today nothing out of the ordinary happened and on the way back I couldn’t get over 5mph the rpms were moving and got up to 3000 but the boat wouldn’t accelerate. Any ideas?

[Gugi47]

Welcome to the site.
Any noise?

[Bobportante]

No the engine sounds fine once I try and push it I get a slit rattle tho

[mmwjr]

Welcome aboard

So the engine was turning 3000 rpm and the boat was going 5 mpg, correct? What outdrive? Sounds like either a spun prop hub or engine coupler.

[Gugi47]

That's why I ask for any noise.
I guess is the engine couplet.

[jparsons121]

Any smell of burnt rubber in the ER. Coupler spinning will usually be accompanied by a strong smell. To check prop, make alignment mark the outside hub of the prop and on the nut/shaft. I use a small punch to make the marks.
Note the alignment of the marks and make a pull in gear simulating the normal operation. Shut down and observe the marks. If they aren't aligned anymore, the prop hub is slipping.

[Bobportante]

Thank you all for the advise, I will update you when i diagnose the problem for sure.

[Bobportante]

its a bravo 3 dual prop drive

[Bobportante]

it had a little smell of possibly burnt rubber and some one on the boat said they did see a little dark smoke from the stern.

[mmwjr]

Originally Posted by Bobportante

its a bravo 3 dual prop drive

B3 has solid hubs so it’s the coupler. The engine needs to come out to replace it.

[Bobportante]

Does any one know common ways an engine coupler fails? Just trying to get an understanding, just bought this boat last week been out on it for less than a few hours and didn’t think I was doing anything to harm the boat?

[mmwjr]

A coupler can fail from the following:

Age, vulcanized rubber connects inner and outer metal and is designed to break away to protect the engine but after many years the rubber deteriorates.

Prop striking something.

Failure in outdrive locking it up.

[Bobportante]

Thanks so much for the info very helpful and nice to know I can reach out with questions, do you know what an average cost to pull out engine and replace a coupler?

[Gugi47]

Originally Posted by Bobportante

Thanks so much for the info very helpful and nice to know I can reach out with questions, do you know what an average cost to pull out engine and replace a coupler?

2K or more. They have to remove the drive too, for line up the engine when reinstalling....
I suggest to get a kit that includes the bellows, gimbal bearing, water hose, and shift cable and replace them to. They will save you big box. And you pay last in labor having all that out anyway. Just a suggestion...
Good luck.

[mmwjr]

Originally Posted by Bobportante

Thanks so much for the info very helpful and nice to know I can reach out with questions, do you know what an average cost to pull out engine and replace a coupler?

I don't know the labor rates wherever you are located. $100 per hour x 8 hours. Also if you transom assembly have not been rebuilt with new bellows in the last 5 years I would do so as already suggested.