Replacing mercruiser 485

[Firsttimer92]

I have a 82 vip 17’ that has a 485 set up but unfortunately the previous owner lied and the block has water in cylinders and a cracked head. I’m not real familiar with these motors but I found and 86 trident dynasty that has a running 170 in it for $500 so I bought it and yanked everything out but here is my dilemma. The 485 transom assembly’s mounting bolts are wider set than the 170 so my question is can I just swap the bell housing from the 485 to the 170 or do I need to swap the transom assembly?

 

[achris]

You can go either way. The wider mounting, 14",is for drives and engines up to 1982 (MC1). The narrower mounting, 10", is for 1983 and later (R, MR, Alpha One)...

Personally, I would move to the later transom and drive. Then just change the exhaust manifold from the broken 485.

Chris...

 

[Firsttimer92]

Well the feller put a 165hp out drive with the 170 and the gear ratio is way off but my 485 out drive is geared correctly for the motor. I just wasn’t sure if the bell housing would mount up to the 170 with no problem. I’ll probably swap out for the 10” transom assembly so I can put new seals in while it’s out

 

[achris]

The 165 (the old inline 6) drive ratio was 1.65:1. Your 170 is 1.84:1, as is the 485. As it's only 'one' ratio different, a simple prop swap will get you back in the right RPM range.

 

[Firsttimer92]

Ok well I’m just getting clarification but I can use the 485 flywheel housing on the 170 with no problems or do I need to just use the 170 10” transom assembly? I’m still learning.

 

[achris]

The ONLY difference between a 170 and a 485 is the exhaust manifold. Everything else is the same (it's completely the same engine), so yes the flywheel housings are interchangeable.

 

[Firsttimer92]

Ok I really appreciate the advice. You can’t find anything on these motors but the basics.

 

[achris]

Ok I really appreciate the advice. You can’t find anything on these motors but the basics.

Everything you read about the '470' applies to the 485. As I said, same engine with a better exhaust manifold.

Chris.

 

[Firsttimer92]

Well I put the housing on and not sure of a few things. Looks like the coupling is recessed too much and the old cover held the starter bolts where as the 485 cover doesnt.

 

[Firsttimer92]

My 485 exhaust is trash from a crack going down inside. Reason why the motor got water in the cylinders but my 170 has the aluminum exhaust which I have read is a bit better so I replaced the flywheel housing with the 485 but it looks very deep for the coupler. Do I need the 485 starter and flywheel and coupler to?

 

[achris]

If you're changing from an Alpha One set up to an MC1 set up, you'll need to change the coupler too.

 

[Firsttimer92]

the flywheel to?

 

[Bondo]

the flywheel to?

Ayuh,.... Whatever is Necessary,....

Please keep yer questions in this thread,....
I deleted the other one you started,....

 

[Firsttimer92]

Ok

 

[Firsttimer92]

If you're changing from an Alpha One set up to an MC1 set up, you'll need to change the coupler too.

Sorry for the unending questions but does the couplers just swap out? I know the 170 bolts to the flywheel and the other bolts to the crankshaft. Do I need the 485 flywheel and coupling or just the coupling?

 

[achris]

It's going to be easier to remove all the old MC1 transom, drive and engine and install the Alpha One. I'm not there and can't look at what needs to be changed and what doesn't. And creating a FrankenMerc is only going to lead to more problems in the future.

Chris.....

 

[Firsttimer92]

Ok I appreciate it. Seems like it’s getting deeper than I wanted it to be. Ballin on a very small budget

 

[Bondo]

Sorry for the unending questions but does the couplers just swap out? I know the 170 bolts to the flywheel and the other bolts to the crankshaft. Do I need the 485 flywheel and coupling or just the coupling?

Ayuh,.... Look at the flywheel,.....'Does it have the threaded holes ya need,..??

If not, then youl'll have to swap the flywheel as well,.....

 

[Firsttimer92]

Well it has the flywheel mounted coupling but I was just curious if the 485 flywheel would swap out without messing anything up

 

[Scott Danforth]

Ok I appreciate it. Seems like it’s getting deeper than I wanted it to be. Ballin on a very small budget

no such thing as a tight budget and boats. Boating is seriously more expensive than racing (racing you have sponsors to help) owning a platypus engine like the 470/485 also means you must have deeper pockets than if you had a V6 or V8

Well it has the flywheel mounted coupling but I was just curious if the 485 flywheel would swap out without messing anything up

cranks the same between the two. you can swap flywheels between the 470/485 as they are balanced the same.