470 to 4.3 conversion. What needs to be done?

[littlelund]

Tossing the idea around of setting a pulled out merc 4.3 in place of my merc 470 in my Starcraft Islander 26ft. I hear alot of people say swap the 470 out for a 4.3 but I'm having trouble finding info on actually doing that. Since the 470 doesn't have side mounts and the 4.3 does where do we start. The Islander has two large aluminum beams running front to back in the engine pit so the support beams are there although the width may or may not be correct. Has anybody actually DONE this conversion and even better if someone has done it to an aluminum islander.

 

[cj8mule]

Re: 470 to 4.3 conversion. What needs to be done?

Here's a close example. He started with a 120 OMC and I believe he put a 4.3 in it's place.


http://forums.iboats.com/boat-restoration-building-hull-repair/1976-22-starcraft-islander-rebuild-369247.html

 

[Bamaman1]

Re: 470 to 4.3 conversion. What needs to be done?

You would want a complete I/O unit to transfer over: engine, outdrive, transom plate. Like a donor boat. Mercury are masters at making sure nothing will fit easy in anything. With the 470 transom plate, I don't believe any other engines will fit.

Now has far as fitting in that boat, I'll have to bow out on that one. It's doubtful you'll find any engine transplants for that specific boat.

 

[littlelund]

Re: 470 to 4.3 conversion. What needs to be done?

cj8mule thanks for the 166 pages of reading I'll sit down later and start reading it looks interesting.

Bamaman1, thanks, the islanders came with the 4.3's after they did away with the 3.7's so I know they will go in there. I plan on buying a new SEI outdrive which the 470 and 4.3's both use the 1.84 ratio's. My main concern is mounting the engine and figuring out what needs to be done with that. I want reliablity and although running good, the 470 has a lot of hrs on it (although mostly trolling speeds) So I'm contiplating a 470 rebuild or a 4.3 engine swap depending on cost and what I can find in the used pull out market. Driveline is currently pulled so nows the time to start thinking about it before spring.

 

[cj8mule]

Re: 470 to 4.3 conversion. What needs to be done?

cj8mule thanks for the 166 pages of reading I'll sit down later and start reading it looks interesting.

LOL. Sorry about that lund. It's a good read ha ha. I think you can get what you want in the first 100 pages though

 

[Bondo]

Re: 470 to 4.3 conversion. What needs to be done?

Tossing the idea around of setting a pulled out merc 4.3 in place of my merc 470 in my Starcraft Islander 26ft. I hear alot of people say swap the 470 out for a 4.3 but I'm having trouble finding info on actually doing that. Since the 470 doesn't have side mounts and the 4.3 does where do we start. The Islander has two large aluminum beams running front to back in the engine pit so the support beams are there although the width may or may not be correct. Has anybody actually DONE this conversion and even better if someone has done it to an aluminum islander.

Ayuh,.... What Vintage Islander/ drive,..??

I pulled a 2.5l/ MC-1 outa my 221 Islander, 'n dropped in a 4.3LX/ Alpha drive...

You mention replacin' the Drive in yer next post, the Drive ain't the issue though, it's the Transom assembly...
hence, I ask the Vintage yer startin' with...

As for Motor Mounts,....
I bent some .090" aluminum plates, 'n riveted 'em to each stringer at the tops, 'n to the ribs at their bottoms...

'n like Bamaman1 says,... Find yerself a Donor boat, with the complete driveline ya want,...
Piecing it together, part by part co$t$ 10 time$ More...

 

[stonyloam]

Re: 470 to 4.3 conversion. What needs to be done?

OK here is my opinion, and I am an admitted 470 fan. Why bother? If your 470 is in good shape, keep it. You talked about a rebuild, well it is likely that a "cheap" 4.3 will need a rebuild anyway, and a good 4.3, will be expensive. What I would do is find out exactly what shape the 470 is in. Do a compression check, and if all is good with compression around the 150 mark you should be OK. Plan on replacing the waterpump cam seals. You might want to just pull the head and do the valve guides and seals and maybe put in hardened exhaust seats (use a OEM Mercruiser head gasket). A update with a Petronix Ignitor II and flamethrower II coil might be something to think about. I know there is some talk about parts NLA, but most of those parts don't ware out, they are castings and covers and such, and all are available used on e-bay, so I would not worry about it. The big advantage of the 470 is if you are doing some cold weather fishing, just take 2 min to drain the exchanger on the ramp and you are freeze protected, you can fish all winter if you like. Anyway, just my opinion, good luck with whatever you decide.

 

[littlelund]

Re: 470 to 4.3 conversion. What needs to be done?

Bondo the engine plates was kinda the route I was thinking as well. It's an 84 26ft islander with a 470 and a Alpha 1 gen 1 1.84 upper that locked up so instead of fixing old stuff I'm going to buy a complete SEI 1.81 upper and lower. I've redone every bit of wood except the cabin bulk head, new floatation foam, new cabinets, new interior, new transom, rebuilt gimbal housing, etc etc so all that will be left is the engine. To make the project complete feeling a rebuilt engine of some sort would make it feel complete. But I'm running into expense vs value of the boat so I have to weigh options.

Stonyloam, I'm with you to a point. for some reason am always drawn to the underdog (470) but like the idea of a little more power with a better engine. I'm just kinda feeling things out. The 470 does seem to run well and probably could just use a carb rebuild and some of the problem area's touched up for now. Add a reliable kicker for insurance and I'd feel aright with it, atleast until it breaks in the middle of lake huron

The link cj8mule posted is being very helpfull.

 

[stonyloam]

Re: 470 to 4.3 conversion. What needs to be done?

Add a reliable kicker for insurance and I'd feel aright with it, atleast until it breaks in the middle of lake huron

OK, I just can't let that go LOL! There is a misconception out there that the 470 is a unreliable engine. This is far from the truth. The 470 has some problems, in particular the tendency toward head gasket failure if overheated, but this is a chronic problem that is not likely to leave you stranded anywhere. A well maintained 470 is every bit as reliable as any other of the Mercruiser marine engines (IMHO). I have had mine for 21 years, and even with a bad head gasket it has never failed to start and run well enough to get me home.

 

[littlelund]

Re: 470 to 4.3 conversion. What needs to be done?

Stonyloam I can't argue with you. My neighbor owned it since 84 and I don't believe it ever left him stranded in the 2000 hrs on the gauge, infact it was the only thing he felt strongly enough about that he gaurenteed it ran good. Funny part is other than changing the oil and doing a alternator conversion I don't think he ever touched anything on the boat. His motto was "fish it, don't work on it"

After playing with the engine again today in the shed, I think i'm going to do some preventative maintaince on the beast and see how it goes next year. It does seem to run very well. I've been teetering between 3.7 vs 4.3 but I think I'm going to give this engine a shot. If the time comes where the 470 needs a major overhaul I will probably spend the money on a 4.3 swap.

 

[stonyloam]

Re: 470 to 4.3 conversion. What needs to be done?

That is great. Just remember a new impeller at least every two years, and keep it cool. Then on those 70 degree November days when all the others are "put way for the winter" you can put the (aft) plug in the exchanger and go get some of those late fall perch. Drain the exchanger on the ramp when you pull it out and you are good. have fun. Welcome to the 470 club :facepalm: LOL