Couple of dumb I/O BBC newbie questions Help!

[Needafunboat]

If winter were still around, he'd get a kick out of this post. A few years ago he and I were politely competing for the few nice starliners around, I gave him a bunch of crap when he got that persuader - and now I'm lovin' my new sterndrive! Far less trill, but better for the family in cool MI weather and gobblin' up the miles on bigger inland lakes.

To the questions -

1) My new boat has a 1995 454 mag (EFI) in it. I found some specs online - 8.6:1 compression and it says to ONLY use 87 octane, which makes NO sense to me. The regular 454 (8.0:1) has no such warning. For the amount of gas I run in a summer the price difference between 87 and 92 octane is nothing - especially compared to a motor. Any thoughts on what to run???

2) What's the redline on that motor? Is there a rev limiter on it in stock form? I was out to around 4800 rpm (per dash tach anyhow). I'd like to wring it out and see some bigger #'s, but again don't want to take a chance for the price of a motor.

BTW - motor has about 450 hours on it, 7 cylinders are good and the troublesome rear port cylinder (#7 or 8?) is within spec, but lower than the rest. Boat runs well - 65.2 GPS on a my first run - medium/heavy weight load, short blast without messing with trim much on a kinda gnarly 23p mirage. Boat weighs around 3550 lbs dry and is sort of like a chubby/wide 234 persuader. 1995 stingray brochure says 68 mph on that boat / motor with a light load. I should be able to hit that with less fuel and more seat time to get the trim right.... If I don't run out of rev's.

 

[boatn70]

seems like the mag motor should rev i little higher than that...
my non mag setup had a rev limit of 4800, the 502 mag efi has a 5050 or 5250 rev limit i think....
there may be a sticker on the intake, tstat hsg or valve cover that details some of this stuff, merc seemed pretty good at doing that. your boat seems like it turned out to be a nice deal for you!! glad to hear it.

 

[convincor242]

If it is a Mag motor the rev limiter should be 5250 as boatn 70 has stated at 450 hrs of hard use it may need a freshen up valve job and springs, cam could be wearing, this is probably a gen v motor not a gen VI motor you can check all this stuff if you have the proper measuring tools but it is a great motor to start with so run the heck out of it you will get mor speed with seat time!!

 

[Needafunboat]

Thanks guys - I checked the motor (just too obvious for me to do before I posted!) and it says 4600 to 5000 rpm.

Thanks Kevin - the boat is turning out pretty well. I do have a few $K into the interior, plus a grand into the trailer/outdrive - but it's a nice package for the $. We had an absolute blast on it last weekend - just so much more family and big water friendly than the starliner.

As suggested, I'll run the boat as is for a while. For our family uses, there is absolutely no reason to add more power - but I know I'll get the itch. There's a nice set of IMCO's near me and it's hard not to do it!

Convincor242 - any idea on what it would cost to freshen it up over the winter?

 

[convincor242]

Freshen up

Well that is a tuff question to answer properly it all depends on what you want to do you can give me a call I will give you some better answers when I find out what you want to do but I can certainly help you out, Mike Huyser 6164518333 ext 165 @ Oliver connecting rods

 

[Jetmate]

It doesn't make sense to me why you couldn't use higher octane fuel. The rule has always been you can go higher but not lower if you have a high compression engine. IMHO

 

[Needafunboat]

It doesn't make sense to me why you couldn't use higher octane fuel. The rule has always been you can go higher but not lower if you have a high compression engine. IMHO

Same thing I'm thinking - what's it going to do - anti-detonate??

I ran 92 from the gas station last time out. I'll probably stick with that when it's available.