454 repowering on a 270 Sundancer

L

larsoslo

Member
Jan 1, 2014
63
Oslo, Norway
Boat Info
270 Sundancer 2000
Engines
383 Merc Stroker 6.2 w/Bravo III
I've read dozens of threads on 454 repowering, but it seems like most threads are for larger cruisers with multiple engines or smaller ones where the 383 stroker is a natural choice. I have a 270 Sundancer DA and have received an offer for my engine which is working fine but has 1200 hours on the clock. It is tempting the seize the opportunity and repower. Does the 383 stroker work for this boat or do I have to make the uncomfortable stretch to the 496? It's important that I can reach plane with 5 people on board. Time to plane isn't important, but getting there is.
 
502 is always an option! The stroker will not have the torque for 5 people in my opinion.
 
you can 'enhance' the planing performance of a boat with trim tabs (and the size of trim tabs) and a different (lower) pitch prop....so if you do go with a 383 stroker and find it a little weak for your needs you can make these adjustments.....you may need to change the prop pitch anyway for whatever new engine you install since the performance (torque and horse power curves) of the new engine will likely be different than the original 454....

cliff
 
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This is true. I would be very interested in hearing from someone with first hand experience though. The lower weight of the 383 is a tempting thought.


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The 6.2 was designed as a drop in replacement for the 7.4. It is a high rev engine with a near flat torque curve. You won't find that information anywhere in Merc information, however, other places that stroke engines readily provide it. I don't think you will have a problem if you can deal with the high rev noise. A minor prop change may allow you to come down in RPM without laboring the engine. That is what I did.

I have twin 6.2's in Saint Max and have no problem with the engines pushing the boat as well as a 7.4 equipped 330 of the same age. I keep up with my 7.4 counterparts at cruise at a very reasonable RPM in large part due to enhanced trim tabs.

I have not been to Norway in 3 decades. Last time I was there gasoline was well in excess of $5.00 USD per gallon. My 6.2's burn roughly 19+ GPH (total) at 22 knots. My counterparts with 7.4's burn roughly 23 GPH (total) at 22 knots. Something to consider.
 
I am leaning towards the 6.2 now, largely because it seems like it's a better fit - and should be much more fuel efficient at slow speed with the lower weight in the back. With the new hydraulic steering with autopilot, I am planning to go slow a lot more than I had the patience for when I was stuck at the helm at all times.

Gas is now $8 per gallon here, so it's definitively a concern. But after changing all instruments, steering, heating, engine, etc - I am looking forward to spending some money on gasoline. :)
 
Have you talked to a performance marine shop? Most of the stroker upgrades I have heard of are coming from a 5.7 or smaller to gain torque and of course HP. Think there is a lot of truth to "No substitute for CID". The 8.1 is a well proven workhorse and a small block needs to work a lot harder to keep up to it. There are a few ways to get your 8.1 to lighten up and you would not have to mess around with all the bolt on and acc changes. The 383 is an awesome engine but I think at end of the day your money would be better spent on what you have.
 
If you switch from a 7.4 to a 6.2 wouldn't you have to change gearing in the outdrive due to the higher rpms? Doesn't the 6.2 have a higher hp and torque rating? I understand it needs to work a little harder to push those numbers out put your also dropping a couple hundred pounds.
 
To the OP. To keep me out of the big block, small block debate, you may want to look at the total cost of ownership of each engine. I know taxes are a beast in Norway.

I believe the 8.1 plug wires are close to $50 each. Does the 8.1 require high octane? Where is the torque created? Is the 8.1 a long term engine for Merc? Etc. that may help with your decision.
 
A late follow up to this thread. I replaced my engine early July and have not looked back since. The 6.2 performs much better than I feared and there is sufficient torque to plane with 4-5 people on board (haven't tried with more) and the lower weight certainly shows on waterline. As an added bonus, the engine feels significantly smaller in the engine room as I can now more easily move around.

No gears or props were changed from my BIII with 22" used for my previous 454.


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