Repower 1999 7.4 Sundancer with new 8.2 freshwater Mercruser

[jgyatesjr]

Good thoughts - I will look into this. You know the standard engine for the 260 was a 5.0L (220 hp) with Bravo II. Optional engines: 5.0L EFI (240 hp); 5.7L (250 hp); 5.7LEFI (260 hp); and, 7.4 (310 hp).

I note that you have two 5.0 in your 300. You wish you had big blocks?

 

[Jimmy Buoy]

If he replaced the engine with a volvo, wouldn't he have to replace the outdrive as well? I didn't think you could mix and match.

In any event, he's going to have to make sure that the gear ratio in the drive matches whatever he repowers with.

You would definitely want to check on that, but you might just be able to couple the same bell housing to the back side of the motor. The block is a GM block from what I've read. Most marine engines are cast blocks from GM and then marinized from there.

Just looks like a concept that is long overdue in the marine world. You get so much more useable torque from a variable valve engine. From the test results provided, the heavier the boat, the better this small block fared against the 8.1.

 

[jgyatesjr]

Update: I now have a new transom assembly and a new Mercruiser 383 Stroker with freshwater cooling. Only have 2 hours on the new engine but I now hit 38 mph at 4200 RPM (WOT is 4800 to 5200 but I haven't tried to do that yet – too new.) Boat sits much higher in water (2 to 3 more inches of bottom paint now showing). It’s only money and whole lot less than any new mid-sized car you can buy.

 

[Lazy Daze]

I bet you're itchin' to hammer down! Thanks for the update.

 

[Pour Bouy]

What size boat ? Were you happy with the Stroker ?

 

[AJSB]

Did you have to switch out props? What size are you running?

 

[jgyatesjr]

To close this out I went with new fresh water cooled 6.2 (383) Mercruiser Stroker. But, it only last 35 hours before rear port spark plugs had disappearing electrodes. Mercury dealer first said I was overproped. But unlikely. The 454 had a Bravo 3 with 24 pitch props; the installer replaced with 23 pitch but still didn't achieve 4800 to 5200 rpm at WOT so we put on 18 pitch. Just when I started getting to 4800 rpm the engine died. Anyway, Mercury is replacing the engine but now claims that the aftermarket fresh water cooling system was the cause. The cooling system is a MPS4320-B by Marine Power Systems in New Jersey. They said they have installed many of these systems and have never had an issue. So, who to believe. Anyway, Mercury is replacing the engine but will not provide a warranty if I install the aftermarket cooling system. Guess I have no choice in the matter. Hope to be in water in April! What a saga.

 

[PlayDate]

I'm sorry I'm late to this thread but no one ever asked you how many hours you had on the original 7.4s? I'm just curious. I sincerely hope the strokers work out for you.

I had a similar problem on my boat 10 years ago and ended up replacing the heads with aluminum marine Edelbrock heads. That created a new problem of having to change the props from 17"x16" to 17"x18".