Peak Power on 330 Mercruiser
 

I wondering what rpm peak HP is made on a 84 330 Mercruiser. The motor is stock as far as I know. Where should I set a rev limiter at?

Thanks Rob

set it at 4500

BOY DID I MIS READ IT WAS A 330 NOT 365 ,,BRAIN FADE ::(

SAVE THOSE ROD BOLTS 4500 ,,

set the rev limiter whereever you want, but keep in mind that engine is not designed to be run over 4600 rpm. the main reason being that the rod bolts are not meant to handle the acceleration and deceleration and subsequent induced stretching and compessing of the piston and rod assembly over 4600 rpm. as they stretch out of spec, the rod bearing will move in the rod and eventually spin or worse. also , and this will probably happen first, you're beating the **** out of your valvetrain over 4600. those ****ty little single springs just aren't up to the task, an dthe valves will float and eventually hammer the head off a valve even thoght you don't think you hear the floating. but then again, there always someone who gets away with it! hope this helps.

That engine has cast pistons that will crack at sustained rpms above 5,000. The mags can be reved higher.

I think Cord means( may crack) not will crack mine run 5100 all the time,but then again I have ARP rod bolts.

wow maybe this motor has been apart. When I bought the boat it had a 15p al prop on it and the motor spun at around 5200 all year long. I didn't know any better. Then i started to try an figure out why it was so slow and changed to a 21 prop rpms dropped to 4200 now. I m considering buying a 19p prop to get the rpm back up to 4600. I have ben told this would give me good performance. But now I'm concerned rpm might be too high. I dont think it has a rev limiter at least I never hit it. I'll have to get one and set it at 4600.

Thanks guys.

Rob

you don't have to get a rev limiter. just pay attention to your guages evry 20 sec. or so, and prop it out right. also you should really think about replacing that poor old engine! great idea, since i'm not paying!

This will be the last year for this motor. But its been running so good I hate to touch it. I think it has about 500 hours on it now. I'm just planning on rebuilding it and upping HP to 400 maybe 450. I want to try and keep it reliable, lower comp. so I can run any gas. I don't want to start having drive problems by going too radical. I hear the TRS drives are ok till around 500hp.

with a good trans, and if you don't abuse it They'll handle more than that.

Yea I don't really want to sink that much into this boat though. I will probably sell it soon for something a little bigger with twins.

Rob

You probably wouldn't have any problem making 400+ hp out of your 330. If it's an original 1984, you have big port oval heads which can be used with some work to them (many posts on these heads). Your weak link may be your tranny depending if it's a Merc or a Borg Warner. We 500 hp behind two Merc trannies in a Scarab with no problems. When we added blowers and upped the HP over 600, we started shredding Merc Trannies. The Borg Warners are supposedly stronger. We had no problems with the TRS drives themselves.

I'm not sure which tranny I have. Is it marked somewhere. I'm guessing its orginal. Did they put the Borg Warners in them from the factory or is that a after market tranny?

Rob

They came from the factory. The 1981 Scarab had the Merc trannies in it. My buddies 1986 Scarab Panther had the Borg Warners in it. No problems whatsoever with the drives or trannies in the 86. Did blow a flex plate, but that was about it. Not sure what year Merc switched or if they sold both at the same time.

I'll have to look at mine. It should be marked Borg Warner somewhere right?

Rob

It should say something I would think, but can't really remember. If you can find a diagram somewhere, the differences are pretty obvious. The Merc Trannies are very small in comparison to the Borg Warners. If you only plan to run 400-450 hp, I think you would be fine with either. The 81 Scarab was hamered pretty well and the Merc trannies stood up with 500 Hp...

The MerCtrans II is a one piece bell housing/tranny unit. Merc used B/W's in their higher HP stuff but did put the MerCtrans behind a # of 330's. They also used both the 71C and 72C B/W's in their TRS performance stuff with the 72C being stronger and an inch longer that the 71C, which in turn is over 6 inches longer that the MerCtrans II. Confused enough yet?? --- Jer

yea thanks. im really confused now. I'm going to check it out sometime this week. wil it be stampd 71c or 72c somewhere?

Yeah, or 1017 or 1018 for the B/W stuff. --- Jer

Great thanks!!

Rob