Repower Opinions

[harnett]

I respect and appreciate your point of view. People sportfishing want to go fast. The boat I have is a 53 CONVERTIBLE. Highlight on convertible. I've owned her for over 25 years and there has never once been a fishing pole on board. I guess you don't get that not everyone with a convertible wants to fish. I was hoping for more of a engineering discussion on the technical aspects of what I was proposing. The 53 motoryacht I thought was the exact same hull as the convertible. Can anyone confirm that? The motoryacht the guy I'm talking with did had the 6TA at 450 hp installed and she performed the same as with the the 8V71T. That made me believe that my boat could get at least equal performance with equal HP/ lighter engines. I will give Cummins engineering a call to discuss as suggested. Thank you.

[Boatsb]

Repowering a convertible with small engines will make it harder to sell and get your money out of it.

Look at other convertibles that have been repaired and talk to the people that own them.

[motoryacht lover]

I think what Boat SB is saying is that all things being equal that maximum longevity will be obtained with a larger displacement engine producing the same horsepower as a smaller displacement engine. I am no engineer by a long shot but don’t know if the larger displacement engine will produce more torque at a lower rpm in other words will the large displacement engine keep your boat on a plane at a slower speed and in helping handling in a following sea climbing the backs of the waves, coming in an inlet, etc. I like my power when in a following sea, seems to be less fighting the steering wheel and overall more control.

[jim rosenthal]

You are getting all the good suggestions, here. I would not repower your boat with C series Cummins. either get the right size engines, or put the money away and keep saving until you can do it right. Any of the big engine options would do fine for you. The C series option isn't big enough- they may run and move the boat, but sooner or later you will regret not putting in the larger engines.

Looking at the larger picture, 750hp or more per side isn't actually a lot of power in a 53 convertible, especially one that heavy; these were very robust boats and they weigh a lot. While it's good to stay inside your budget, in this instance you will wish you went bigger.

Look in B&H and see if you can find a set of 3406Es or Series 60s, like he said. You could also call T&S Marine Engines in Crisfield, MD, and see if they know of anything. They are Cat and Cummins dealers and also rebuild a lot of Cat engines in their plant.

Good luck on this. Go big now, or keep your powder dry and wait for the right deal to come along.

[Cricket]

Scott, Series 60 is a great option, didn't think MTU was still selling them in the marine space but they are so parts would be available for take outs or remans. An outfit like Gregory Poole or Jarrett Bay most certainly have already repowered some 53c's so they could be a good resource. They probably already have the engineering for the mounts which could save a ton of $$$$$. Slane Marine did the engineering for our 3406e mounts, Gregory Poole made them or had them made, and they fit perfectly right on the marks the first time. Also, Ring Power could be a good resource for info.

[Boatsb]

The mound design is the easy part


Hang the motor in place.

Make mockups out of duct tape and cardboard.

Have the local certified welder make them out of steel plate 2 sizes thicker than recommended and send for powder coating.

I did this the last 2 repowers I did and it all was fine.

FWIW the custom mounts looked better than the factory ones we compared them too..

[krush]

I left this post over on thread about a 46c repower...applies even more to a 53. I think m11 is too small for a 53.

:https://www.samsmarine.com/forums/sh...ng-my-1980-46C

Cummins c series 8.3 liter are mechanical are going to be too small for a 46c. I have c's in my 41 and it tops out around 30-31 knots and easy cruise at 18knots doing about 18gph total. The 41c is much lighter and much flatter ass and requires way less HP. A 46c needs m11. Save your pennies and do it right.

[jim rosenthal]

Actually Slane Marine did a 53 convertible with M11s, and it topped out at over 28 knots on sea trials. That is fast enough for some of us, esp in an older boat.

[thoward]

Pulling 10k pounds will change your COG and likely have an impact on your ride/behavior especially at hull speeds. I would be very concerned about raising the COG, My 60C enclosed bridge with a tower was absolutely miserable in a beam sea. Tim Powell on HOF can give some first hand insight as to the difference in ride of a 52C with QSMs and a 52 with 892s. Yesterday, I had to run 170 miles in 3' @ 3s quartering seas. No way we could do it at hull speed so we ran at 19 knots and I was certainly happy to have that extra displacement.