212 engine performance
 

I have had my Mariah since November @ 76 hours. I am currently at 98 to date. Runs good, smooth new stereo is awesome. My question is perfomance. I dont think my engine is performing like it should @ est. 250 hp. I had an older boat that had a 4 barrel quadraunk on it that screamed. I do have a new 21 pitch Mercury Mirage just added this weekend. It had the old 21 pitch alluminum that I keep for backup. Trimmed up with 600 lbs of people in it only turns a little over 3900 Rpm @ 42mph. That is plenty of speed, but I would just think it could handle a little more. I guess I need to do a complete tune up and put a new fuel filter on it(possible restriction). The boat DOES NOT hesitate, thats why I havnt done all this yet. Any ideas?

Yes, it sounds like your boat needs a tune up. Normal WOT rpm's are 4200-4800

Yes, something is certainly off. My 202 with nearly the same power package (I have a carbed 4bbl) will do 50 mph with 4 persons and a full load of fuel.

I don't think your prop is the issue. I've run both aluminum and a stainless merc vengence of the same pitch (21p) and the performance is approximately the same: 4600 to 4700 rpm@WOT.

my 212 runs at 4700 rpms at wot and does 60mph with 4 people in the boat. I have a 23p 5blade stainless prop called the high five.

darrel,

I looked at the high 5. I found this one locally on craigslist for $250 and it doenst have any marks or scuffs on it, practically brand new. I priced it new and it was nearly $500 for the prop and hub. I wanted to get more pitch but if im only turning 4000 rpm then a more pitched prop will make it turn under that. If the funds allow this week im going to put a set of plugs, cap, rotor, and wires and do a service on the engine. Maybe for some reason im not getting all the through out of the throttle. I will look over this week.

also, keep in mind, mine is NOT a 350 mag. Its only rated @ 250hp.

I don't want to sound like a broken record, but I had this exact same symptom last year. Mine also had a little knocking/growling noise that I wouldn't have known was wrong since the boat was new to me. Turned out to be the gimbal bearing. Does your's have any sort of rattling noise while at idle?

no, but if you rev the engine more than an idle it does seem to make a little noise. The previous owner had the drive takin off, and everything changed. However, I dont know what "everything" is.... Is there any other ways to check the gimble bearing. SOB im gonna be mad if I have to pull that heavy thing. How hard is that to change? I do have a foklift so it wont be that big of a deal. I will definetly run her on the hose tomarrow and listen CLOSE. It seems that when im turning at an idle there is a definet noise.

well after reading this http://www.sterndrives.com/precisionparts/421.html I have figured that the gimble bearing is the suspect. NO MORE BOATING for me for a while. Typically how difficult is this task? Can it be performed on a saturday. or is it a TOTAL weekend Task. Im am very mechanically inclined and not worried about doing this, but just tryin to get a time frame. What is the best place to get murcruiser parts online?:shakehead::punch_out:

Now I feel like vomiting!

If you work hard you should be able to get it done in a weekend. I did my gimbal bearing, u-joints, gear end yoke, and shift cable over the span of two weekends. You will need a slide hammer to pull the old bearing out and tool (you can use a wood block and go slow) to knock the new bearing in. You will also need an alignment tool. The first tool I would get is a Mercruiser service manual for your engine and drive!

If its been more than 3 years since the bellows have been changed I would go ahead and replace them as well.

~J

That's a gimbal bearing, mine was doing the same thing, but had a noticeable vibration you could feel in the hull whenever you'd steer hard at idle speed. As soon as it started doing that, i took it in for service, had the gimbal bearing replaced, engine winterized, oil changed, and exhaust flappers replaced for $1700. Gimbal bearing replacement is I believe around $800. It's a pretty serious job, that needs specialized tools, I'd personally leave this job up to the service department. And don't drive on it if you've noticed any of the symptoms described above. It'll only make it worse, (and more expensive to repair!)

Worn u-joints can cause a similar sound, especially if it's only when turned all the way left or right. But if you notice decreased speeds and the noise all the time, it's almost definitely the gimbal bearing. It's tough to tell, because both can cause similar sounds at similar times.

If I remember correctly, my gimbal bearing was around $600. They should be able to cut a deal on the bellows, since they must be removed while servicing the gimbal bearing anyway.

regaurdless if the u-joints or the bearing is bad, the drive has to be removed. Correct? I plan on doing this myself, not this weekend(will be in PA till next fri), but the next weekend. Will a slide hammer pull the bearing out? What is needed to install? What all should I buy "incase" I dont want to get into it one saturday and need parts and the place be closed sat at noon till Tuesday...

Based on the figures quoted here I would suspect a it's a 4 or 5 hour job minimum.

Mercstuff has a nice how to with pictures and lists what you'll need.

http://www.mercstuff.com/gimbalbearing.htm

Lifting the drive off, and re-installing the bellows are probably going to be the most difficult parts of the job.

I would look at a 19" prop. You are not turning that 21 fast enough.

a 350 V8 is plenty of motor on a 21' boat to turn a 21 pitch prop. I had this same problem with mine. 300hp and the thing would only do about 44 MPH at somewhere under 4000 RPM. The gimbal bearing was replaced and now I'm seeing 58 MPH at about 4600 RPM. I don't know how or why the bearing can cause it (other than the obvious... friction), but I'm fairly certain that's what the problem is here.

I upgraded to a SS 14.5" diameter 21 pitch, but I'm wishing it were 14" or 14.25" diameter. I'd like to squeeze out another 200 RPM and hopfully see the 60 MPH mark! I think a drop to 20 pitch would only raise my RPM, not speed. The hole shot is excellent even with the 3 blade 21 pitch. A 19 pitch would send me over the rev limiter before hitting 55 MPH.

I have a ss 21 p prop I would be willing to sell. Its to much for my 20 footer with a 5.0 motor. I wish I have a 350 mag.

Yeah, I'm with Ryan. I run a 13.75x21p Vengance with my 5.7L Shabah, and it's propped just about right for good overall performance.

If the motor can't pull that prop up to typical WOT rpms there is something definately wrong elswhere...

What's the diameter?

It is a Laser 2 14X21 no dings like Brand New. Could get some pic if you would like.

DoubleD... I PM'd you. Thanks for the info.