Swapping out 470 for 260

chris0061 · Feb 20, 2009

For you experts, I rebuilt a Mercruiser 260 and have a 19 foot cuddy with the 170 hp mercruiser wich you all hate, but it runs good, Anyway how much would it take to put the 260 in? I have everything from the belts to the prop.

TilliamWe · Feb 20, 2009

Re: Swapping out 470 for 260

You need to fabricate a way to put side front motor mounts for the V8. It's not hard, my dad did it on a boat.
And when you say you have everything from the belts to the prop, you mean for the 260, right? Other than the gimbal housing and bell, you'll need all of it.

starsnstripers · Feb 20, 2009

Re: Swapping out 470 for 260

Your better off going to an L-6 165hp move front mount forward. I have one in my ole heavy 21.5'er and she goes great. Thats alotta motor for a 19'er. Or a little more complicated a 4.3 v-6. Then ya have to do side mounts, a pain. How olds the boat?

Don S · Feb 20, 2009

Re: Swapping out 470 for 260

Ok, ONE MORE TIME.
Gear is wrong, need different drive
Exhaust port on transom shield probably won't accept Y pipe for V engine
Stringers needed for side mounts.

That's just the 3 biggies, lots and lots of little problems along the way. Things like where to mount shift interrupt system, wiring differences, hatch clearance, etc.

chris0061 · Feb 20, 2009

Re: Swapping out 470 for 260

First, Yes I have everything for the 260, engine, y pipe, gimbal ring, lower and upper. The entire package came off one boat. Second I figured it would'nt be as simple as just swapping everything out. The motor mounts I can fabricate and when you look the boat up on nada it comes with a 260. Its a 86.

Don S · Feb 20, 2009

Re: Swapping out 470 for 260

Yes, the hole through the transom is the same for either a 470 or 260. Only the parts that fill the hole changes.

starsnstripers · Feb 20, 2009

Re: Swapping out 470 for 260

OH, Well I guess if you hav a whole complete pakage from another boat then you have the right drive transome mount, exhaust, etc. and the boat can handle it. Guess, you need engine bed stringers ( whithin the spec height ) for the motor mounts. the rest is labor by the sounds.

chiefalen · Feb 20, 2009

Re: Swapping out 470 for 260

You say that boat was rated for a 260 ? 19 ft boat?

19 footers usually go to a 4.3 max. It should have a plate or sticker in the engine bay, saying max hp.

HT32BSX115 · Feb 20, 2009

Re: Swapping out 470 for 260

chiefalen said:
You say that boat was rated for a 260 ? 19 ft boat?

19 footers usually go to a 4.3 max. It should have a plate or sticker in the engine bay, saying max hp.

Hmm,

Well, I usually never did disagree with Chief Master Sgts.....

Or "The Chief"

But, the 1966 18' Mark Twain I used to have was placarded for up to 310hp.
(which in those days would have been a 409 Chev v-8 and a Merc #2 drive)

My guess is that the boat will probably handle the modest additional HP of the "260" Just make sure you have the right drive ratio and you'll have to experiment with prop pitch..........

Cheers,

Rick

chris0061 · Feb 21, 2009

Re: Swapping out 470 for 260

I may give it a shot, I'll know if my Mark twain is going to run good next month and I get it back together then The 19 footer will be a good next project. I get it in, aligned and good to go I understand about the prop selection. Right now the 170 has a 19 pitch prop and I took it wot one time and it hit 4800 so I think if I was to leave it in I should take it up to 21 pitch.

HT32BSX115 · Feb 21, 2009

Re: Swapping out 470 for 260

What a coincidence....another Mark! When you get the engine out, check your floor and stringers carefully..(My dad replaced his floor and stringers in our 66 V-sonic in the mid to late 70's)........Just about all MarkTwains had rotten stringers and floors at one time or another!
But then....you would probably know that since you hang out on the Twainer board!

Cheers,

Rick

Swapping out 470 for 260

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