Finally left the mecruiser 470 woohoo

[CAPTKEV85]

Hey huys I havent been on in a while but I have had dozens of conversations about the dreaded mercuiser 470. Well the fourth of july weekend I blew the radiator cap 2 feet in the air and floored it to get the beast back to the dock. She ran for 10 minutes then shut down. Well needless to say I gave the boat away. Now I just bought a really nice 1985 sea ray 25 foot seville. With a 260r mercruiser 350 v8 salt water cooled. Boat is in excellent shape marina took care of it. I bought it for 5,000.00 I knocked him down from 6. This year he put new risers manifolds, hoses, and bellows, rebuilt carb, trim pistons, prop, power steering rack, and timing cover. Now I feel she runs great but when I lay the hammer down she just doesnt seem all there. all cylinders fire but wot is 4000 which I feel is too low. I'm gonna bump the timing up alittle to see if that helps and do a tune up. Any suggestions guys, opinions? let me know thanks.

 

[xltier]

Re: Finally left the mecruiser 470 woohoo

maybe the new prop has to much pitch.try one with a little less.

 

[achris]

Re: Finally left the mecruiser 470 woohoo

Do a full tune, like you said, and check compressions too...

If that's not it, then like xltier suggested, smaller prop...

Chris.......

 

[CAPTKEV85]

Re: Finally left the mecruiser 470 woohoo

I think the prop is 14x17 he told me plus he had it reconditioned which i dont like The new props are cheap now a days.

 

[CAPTKEV85]

Re: Finally left the mecruiser 470 woohoo

So is this a better setup then a 470 lol I'm just joking i know its a better setup.

 

[45Auto]

Re: Finally left the mecruiser 470 woohoo

So is this a better setup then a 470

With a 25 year old boat, a well maintained 470 could easily be a better boat than a poorly maintained 260 ....

This year he put new risers manifolds, hoses, and bellows, rebuilt carb, trim pistons, prop, power steering rack, and timing cover.

Sounds like he was chasing problems. Hopefully your WOT problem is the prop or carb, but I would be VERY surprised if a decent running 260 needed anything smaller than a 17" pitch prop. Do like Achris said, do a COMPRESSION CHECK before you waste any more money then do a full tune-up.

 

[stonyloam]

Re: Finally left the mecruiser 470 woohoo

Hmmm... My old 470 turns 4400 with a 14.25- 19. 4000 with a 14 - 17 does seem a little low for a V8.

 

[achris]

Re: Finally left the mecruiser 470 woohoo

Hmmm... My old 470 turns 4400 with a 14.25- 19. 4000 with a 14 - 17 does seem a little low for a V8.

Different boat, different drive ratios.

My original engine (165) with a 1.65:1 ratio ran a 15" prop. The next engine (4.3LX) had a 1.84:1 drive and needed a 21" prop. The new engine (4.3MPI) runs a 1.62:1 drive and needs a 17" or 19" prop (depends on the load and weather conditions).... All in the same boat!

His new boat is a 25' Searay, heavy.... I suspect he'll need a 15" (or maybe even a 13") prop.... If he can get it cheap enough I would change the top box and get the ratio to 1.65:1.... Then he can run the bigger props (more efficient)... That alone would get the revs up to 4400.... And I think top boxes from SEI are real cheap....

Chris..........

 

[Fordiesel69]

Re: Finally left the mecruiser 470 woohoo

Most of the 25' sea rays I looked at locally either had a 15p or a few had 17p on them. Don;t just bump the timing. Detonation can still damage things even though you can't hear it.

 

[CAPTKEV85]

Re: Finally left the mecruiser 470 woohoo

Ok Cap and rotor shot lol changed it out, much better. Compression test shows average 145-148 psi in all cylinders. My local marine shop is telling me most of the sea rays around hear turn a 15p which would bring my rpms up. After the cap change tach jumped 200 rpms any way.