Thinking of changing engines, question about stirngers

berth control

berth control

New Member
Nov 16, 2008
886
Saugatuck, MI
Boat Info
1985 270 Sundancer
Engines
3.7 liter Mercruisers
I am thinking of changing engines in my boat from 3.7 liter 4's to 4.3 V6's. My 3.7's need to be rebuilt this winter, and I estimate it will be about 2,500 each to have them done completely, if I pull and re install them.

Doug Russel sells "certified" rebuilt 4.3's for about 3,500 each. I am thinking about just upgrading to these more powerful, smoother, quieter, and MUCH easier to maintain engines. There are also lots of parts available for them and my 3.7's are really hard to locate parts for, and when you do they are expensive (1,300 for an exhaust manifold, 500 for a distributor).

There are a couple problems though that I need advice on. The marina mechanic tells me that the new engines will work fine with my outdrives (which were recently rebuilt by the PO) but the boat needs new stringers because the new engines will mount differently. Also, I am wondering about how the wires will all hook up to make the gauges ect. work properly. Any idea on how hard it is to install new stringers and what type of cost I can expect? Also what will it take to make all the wiring work?

I am not sure I am going to take on the project, but you really can't decide until you know the cost and time needed, so I appreciate the help and advice.
 
While I love the old boats and would probably do the same thing, I would look at the COST involved with doing the whole rebuild or upgrade. In other words, you can get the new motors for 3,500 each or $7,000 but how much will the labor run? How much will it cost if you have to re-wire, replace gauges and what OTHER things might go wrong? How much for new stringers? In other words, if it all goes well, you might be looking at $10,000 in total cost. How much will it cost if the worst case happens? If you sold your boat and added another $10,000 to the pot could you buy a boat that has that already done or a different boat all together?

While you've got the engines out, take a look at the fuel tank(s) and replace that bilge pump while you can reach it with the motors out!!

Tough decision! It would be nice knowing it has brand new motors and outdrives! I'd get the opinion of a second mechanic just to make sure it can be done and it will fit without having to move the drives. Good luck and keep us posted!! Send pictures!!
 
Thanks for the advice Sundancer, I appreciate it. The reason you bring up is the reason I am THINKING about doing the swap, not for sure doing it. I may just sell my boat and put the money into the next one. But also, like you said, the next one will prob. not have new engines. I have also already re done the interior of the boat and the outdrives were done by the PO. However, I am not by any means married to the boat. Just need more info to make the decision. Selling my boat and putting another 8 to 10K with it will buy me a mid 90's 290 or 300, the biggest I want to trailer to Florida every winter. Is that better than my current boat with new engines? Not sure.
 
Boats are ALWAYS a compromise! It's not an easy decision! I've looked at some of the newer boats and the only thing I wish I had is an onboard generator! It's not worth jumping ship for that at this point. We'll probably own this one until the kids are old enough to get their own boats! Then we'll down size to a 260 ish boat with a generator!! :grin:

Good luck with your decision!
 
I really like the 270 with 10 ft beam. If the boat is in good condition I would consider the motor swap rather than another boat. Another boat is likely to have it's own set of problems. I've actually been thinking of picking up a 270 that is in need of some repair. If I did, I would replace the twins with a single 8.1/B3. That would make a nice boat, and get rid of the expense of maintaining twins.
 
Needing "new stringers" is really kinda vague info from your mechanic.
Just because the engine mounts are in different locations, doesn't necessarily mean it's a big deal.
Depending on what differs, there's other solutions. You can easily sister a new stringer alongside the existing ones, or through-bolt some heavy-duty aluminum angles to the stringers for the new engine mount locations.

There's plenty of ways to skin this cat- find out from him exactly what differs and I'm sure there's a reasonable solution.
 
I guess a lot of that question also depends how much you're comfortable doing yourself. Id be comfortable doing everything (wiring, fuel plumbing, etc) except the actual glassing of new stringers (and as previously stated, how much modification is required?) and then finding a way to get the engines in and out. If you could do this yourself, the added cost might not be much more than the engines - fuel gauge would remain the same, trim, speedo etc all the same, tach would be different but may be able to be adapted (if yours has the 4-6-8 cylinder switch, and the sending unit on the new engines is close enough it may not be an issue). The great thing about a non fuel injected engine is that the electronics are very simple.
 
:smt001 sounds like you need to get the real price from the people who will do the work,and make a choice then:smt001
 
So where did you end up with the stalling problem you had in that other thread? Is that engine toast?
 
Berth,

I would verify all answers mechanics give. When we first looked into putting a big block in an old 260, we were told motor mounts were not in the right place, gauges would not work, cables would not work, motor wouldn't fit, weight would drop the motor below the risers at rest, etc. Most of this information came from marine mechanics. One very knowledgeable source in Phoenix (Bergeron Engineering) said they had done many, and none of of those issues were correct. They were right. Everything worked including the gauges.

If you're going to do it, I would higly recommend a couple of 350's.
 
tobnpr said:
Needing "new stringers" is really kinda vague info from your mechanic.
Just because the engine mounts are in different locations, doesn't necessarily mean it's a big deal.
Depending on what differs, there's other solutions. You can easily sister a new stringer alongside the existing ones, or through-bolt some heavy-duty aluminum angles to the stringers for the new engine mount locations.

There's plenty of ways to skin this cat- find out from him exactly what differs and I'm sure there's a reasonable solution.
Click to expand...


The current motors mount in the front of the motor, the new ones will mount on the sides. There are currently NO stringers anywhere near where the mounts are, so I defanitely need to put some in.
 
Lauralex said:
So where did you end up with the stalling problem you had in that other thread? Is that engine toast?
Click to expand...


It was a combination of a couple little things that kept elluding me, but basically it was a check valve in the fuel line combined with a carb not quite perfect and moisture in the distributor. That is what the marina's mechanic said yesterday at least, I am not sure it's really fixed until I get over there and trial it.
 
keokie said:
Berth,

I would verify all answers mechanics give. When we first looked into putting a big block in an old 260, we were told motor mounts were not in the right place, gauges would not work, cables would not work, motor wouldn't fit, weight would drop the motor below the risers at rest, etc. Most of this information came from marine mechanics. One very knowledgeable source in Phoenix (Bergeron Engineering) said they had done many, and none of of those issues were correct. They were right. Everything worked including the gauges.

If you're going to do it, I would higly recommend a couple of 350's.
Click to expand...


Thanks, I was hoping you would chime in. Glad to hear all your gauges worked fine. That was a concern of mine. I know the motors will fit, 350's were an option in the boat but they were the biggest motor offered and are really tight in the ER, that's why I am looking at the 4.3's.
 
Glassing in a stringer should not be that much work, but it's got to be sized correctly, and just as important it must be tied into the rest of the structure properly. It probably shouldn't just run from the transom to the engine room bulkhead and stop or you'll be setting yourself up for cracking problems. If there's a fuel tank forward of that bulkhead, it might make it difficult to have a good transition.
It'd probably be helpful to find a similar boat with the engines you want (if they were an option - if not maybe the 350s mount the same way?) and take a look at the stringer layout. Maybe somebody on the board has one? Or if you can talk to an engineer at Sea Ray to get some advice on the size and layout of the stringers you require.
 
Are the 350's a tight fit front to rear or side to side? The 4.3 is essentially a similar block size (same bore and stroke) as a 5.7 - just has 2 less cylinders. If my boat tops out at 41 with 4.3's - I can't imagine how much faster it would be with another 90-100hp out of a 5.7! Those poor Alpha drives may not last too long though....
 
Been in a few diff. 270's 4.3 and 305's never 350's , I think the V6's are under powered for that boat. If you were thinking 4.3's I would reconsider and go V8's , same mounts just two less cyl's each. Outdrive ratio would also change. V8's in the 270's is a nice package. 350's would be my choice,it would wake that 270 up.Just my opinion tho.....
 
Eric,
With the V8's. The width span from the left and right motor mounts is 22 1/2" dead center. This should help figure your stringer locations if you decide to do it.
 
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