Repower 2006 320 Dancer i/O 5.7 to 8.1?

[OTH]

Hi folks,

We have a 2006 320 DA with twin 5.7 Horizons with BIII I/O. Currently have 1400+ hours and marina starting to cringe, warning us to start thinking about repower. Current package well cared for and running fine, lead mechanic going on his experience. Our boat has closed-loop cooling, bought new and 10 years in fresh water, with several trips to salt, and now full time in salt water. We sold our lake house and put our boat on Casco Bay, Maine. Loving it!

We are having the drive(s) painted-surfaces redone for salt. Spent 2016 season diving on drive weekly for a good scrubbing. Question to the forum, whenever it does come time to consider repower is it feasible to repower existing drives with 8.1 engines, or should we consider entirely new drive + engine packages or just live with new 5.7s considering cost/benefit trade-offs?

We like how the hull performs in the ocean but when things get bumpy and we're climbing the back side of fairly big seas we wonder if more power would be a nice thing to have. Current 5.7 Horizons rated at 300 HP each, but we seem to loose bite on the duo-props when climbing the back side of big waves. I'm good on the throttles so manage OK but wondering if more power gives us a prop pitch which would have better bite in big seas. We do try to avoid them but when in Maine it's often a fact of life.

We understand I/Os are not the best option in salt, so the best long-term answer may be to get another boat...but the boat we would opt for would cost several hundred-thousand dollars more...so spending some money on a boat we owe little on and already know/like/trust is not an unreasonable proposition.

Looking for input.

Thanks
Jeff

 

[mnm99]

If they do fit, it would be a nightmare to work on. They would almost touch eachother. Not to mention the cost to convert over 35k. I would stay with the small block, but do like a 350hp 383. Use as much parts off you small blocks and save a bunch of cash.

 

[Jeremygavin]

I have bravo IIIs with 8.1s and they are fine. I agree that they are probably large for your boat. My engines are only about 8" apart at the manifolds but I have a 340.

As for losing bite, easy tip it to make sure you switched the "celery" spacer in the drives so that you can tuck the drive in more. That helped me a lot. It is the space on the drive where the trim rams mount onto the outsrive. I have mine positioned forward of the bolt and that allows the drive to tuck in a bit lower.
Second and more expensive improment I made is I went with Hill Marine 4x4 4 blades and that made all the difference for me. I almost never cavitate anymore with these props. Well worth the money especially if you add more power and have to change pitch anyway.

 

[bahamabreisus]

If the boat is running fine, why be concerned. It sounds like the marina wants some work to do. Have a compression check done to see the condition of the current engines, I would recommend having it done by someone other than your marina, just to be sure. There is no reason for those engines not to last quite a few more years.

 

[Vince_nj1]

The newer 330's have big blocks in them. 11.6 beam. The manifolds almost touch. However with I/O's engine access isn't nearly as bad as V-drives. Personally, I wouldn't worry about re powering until you actually need to and then I would drop fresh set of 6.2s back in.

 

[BillK2632]

Unless there are other problems starting to develop, I would not be thinking about replacing your 1400hr engines. That is nowhere near end of life on a well maintained gasoline engine. The death of most engines especially in salt water is water ingestion due to a failed exhaust riser. The fact that you have closed cooling is also a big plus.

 

[northern]

As noted by others repower when you have problems. If your engines do what they did last year and the year before I would keep them until you notice lack of power and or oil consumption. Our engine have 2750 hours on them. If you have been good to your engines they will last a lot longer.

 

[juggernaut1]

Whilst the 8.1s can swing a prop with more bite, in my experience they don't have the torque to drive up the back of larger rolling swells and you need to be on the throttles to maintain rpm and speed.

 

[juggernaut1]

That is only because you are using them in a boat that should have diesels. In the 340 or anything smaller this is not an issue.

Granted the boat would perform better in these conditions with diesels as any boat probably would. However, the local dealer said it was the same to a greater or lesser degree for all gas powered cruisers in our larger swells at the time I was buying.

I've also been part of a convoy to an island which is approx 20 Klms off the coast and was the largest boat in the convoy and all the smaller boats suffered more than mine as the weight of my boat seemed to benefit momentum up the back of the rollers. Following them was painful as I had to keep adjusting my speed down.

 

[OTH]

Thanks everyone for the input, much appreciated.

Will definitely hold off on doing anything until things start to change, and will then have another shop take a look.

 

[OTH]

Thanks Jeremy, I will check out both!

Jeff

 

[mnm99]

I have bravo IIIs with 8.1s and they are fine. I agree that they are probably large for your boat. My engines are only about 8" apart at the manifolds but I have a 340.

As for losing bite, easy tip it to make sure you switched the "celery" spacer in the drives so that you can tuck the drive in more. That helped me a lot. It is the space on the drive where the trim rams mount onto the outsrive. I have mine positioned forward of the bolt and that allows the drive to tuck in a bit lower.
Second and more expensive improment I made is I went with Hill Marine 4x4 4 blades and that made all the difference for me. I almost never cavitate anymore with these props. Well worth the money especially if you add more power and have to change pitch anyway.

He as a 320 though, Beam is smaller, Generator is in the rear