Boats For Sale:
What are the max RPM's? |
Post Reply 
|
| Author | |
davidg 
Grand Poobah 
Joined: January-07-2008 Location: NW Chicagoland Status: Offline Points: 2239 |
 Post Options
 Thanks(0)
 Quote Reply
 Topic: What are the max RPM's?Posted: September-12-2018 at 3:02am |
|
I took the '87 Martinique (351W) out for a run this evening, and decided to run it up beyond the normal cruise/ski/tube speed, and see what the old girl would do. I have never given this boat full throttle since I have had it (bought late August 2018), but, what the heck....lets live on the edge! So, I gave her all she's got, to see what max RPMs would be, and hopin' she wouldn't blow. It has a Acme 542... that is a little nicked on the edges.
Bottom line.....only got to 4000 rpm. I was expecting more like 4200-4400. Is 4000 correct for this boat/prop combo? What would hold it back from the higher range? I do question whether the 4 BBL is kicking in. Would that be a culprit? |
|
 |
|
|
MrMcD
Grand Poobah
Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3778 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 4:08am |
|
I don't know your prop at all but I am familiar with the 351W. I believe the factory says max RPM should be 4400-4600 RPM.
Ideally your prop should keep you in that range. Your engine may or may not be young enough internally to reach full power or your tune up could hold you back a little. Some Hulls are harder to move in the water than others. My 78 Nautique with a 351W would RPM up to 5,200 turning a 13x14 Prop and top speed was over 50 MPH. My brother with the same engine in a Supra TSM Comp turning a 13x13 prop could only hit 4,200 RPM and top speed was 42 MPH. I tuned it best I could, checked compression and it would not turn any higher. The Supra had a spare prop in the boat that was a 13x12 and I suspect the previous owner wanted more snap and RPM so purchased that prop. Maybe the Martinique Hull has more drag than the Ski Nautique hull? Our more experienced members will give you the prop specific information. |
|
|
|
|
8122pbrainard
Grand Poobah
Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 7:03am |
|
Dave,
I'd double check the RPMs with a shop tach. Yes, I too would expect a few hundred more than the 4000. |
|
|
|
|
Orlando76
Grand Poobah
Joined: May-21-2013 Location: Mount Dora, FL Status: Offline Points: 3108 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 7:13am |
|
At 4000 I’m sure secondaries are kicking in. 87 Martinique is a BIG girl, I myself am a little a slow with a girl that big, don’t want to blow a gasket or break a rod.
|
|
|
Please support The Cystic Fibrosis Foundation
1976 Ski Nautique 351 Escort 1993 Ski Nautique purple and black 351 HO PCM |
|
|
|
|
KENO
Grand Poobah
Joined: June-06-2004 Location: United States Status: Offline Points: 11197 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 8:16am |
If you want to check your secondaries you could do what the guy in the link did All it takes is a zip tie that can slide on the shaft that operates the secondaries and you have to drive it on the water under load because they won't ever open in neutral no matter how high you rev it. link |
|
|
|
|
KENO
Grand Poobah
Joined: June-06-2004 Location: United States Status: Offline Points: 11197 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 8:21am |
Well........this will keep me chuckling for a while We don't need any pictures of you in action with a big girl 
|
|
|
|
|
phatsat67
Grand Poobah
Joined: March-13-2006 Location: Indiana Status: Offline Points: 6157 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 1:09pm |
|
Dave, pick up an Inova timing light if you want to spend a few bucks. They are worth the money. The digital version just does timing and RPMS. The digital pro does timing/rpms/voltage/dwell.
I opted for the standard digital because I own a dwell meter already. You can use this to check your timing specs and also verify your tachometer. I would fully expect a good running 351 in a MQ with a 542 to pull at least 4400. The last one of those I drove was surprisingly peppy and pulled the stock prop 4500. Timing Light |
|
|
|
|
davidg
Grand Poobah
Joined: January-07-2008 Location: NW Chicagoland Status: Offline Points: 2239 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 3:43pm |
|
Thanks for all the responses guys. I do wonder if my tach is totally accurate. I have not done any tuning at all on the boat. If it ain't broke.......! Although, even if it isn't broke, I always manage to go in and break something try to make it ABSOLUTELY perfect! I do agree something is amiss. Tach may be off, engine not quite tuned to perfection, etc.
I will have to put this on the long list of stuff that I need to fix. Always something! House, car, truck, kids house, kids car, kids truck....! 
|
|
|
|
|
JoeinNY
Grand Poobah
Joined: October-19-2005 Location: United States Status: Offline Points: 5698 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 4:15pm |
|
That prop if not terribly damaged should have you at all of 4400-4600 with that boat/engine, assuming your tach is right it would be worth popping the distributor cap off and making sure the advance weights are intact and free and maybe setting the points.
|
|
|
|
|
TRBenj
Grand Poobah
Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 4:32pm |
|
Agreed. I would assume that 4krpm with a 542 on that hull isn’t breaking the 40mph mark (this would be good to confirm). If so, it should have more in it than that. I’d expect closer to 42-43mph. Tune up time.
|
|
|
|
|
davidg
Grand Poobah
Joined: January-07-2008 Location: NW Chicagoland Status: Offline Points: 2239 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 7:35pm |
|
I agree. I think a tune up is in order. The boat actually runs pretty "good". But, more comes to light when you pour the coals to it. Tune up, check distributor, maybe even put a Pertronix in there. I know there is more performance to get out of it. Plus, it has been a bit temperamental to start at times, and will stall out when the unfamiliar drive the boat.
You guys like Pertronix? I have had pretty good luck with it in my '68 Ford F250 (390). |
|
|
|
|
TRBenj
Grand Poobah
Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 7:41pm |
|
No. Skip that.
|
|
|
|
|
phatsat67
Grand Poobah
Joined: March-13-2006 Location: Indiana Status: Offline Points: 6157 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 8:53pm |
|
Skip. If the points don’t look overly worn they likely have a good original set in there. Visual inspection and check the gap/dwell is all that’s needed. Verify though you’re ballast resistor is working and you’ll never have issues.
|
|
|
|
|
davidg
Grand Poobah
Joined: January-07-2008 Location: NW Chicagoland Status: Offline Points: 2239 |
Post Options
Thanks(0)
Quote Reply
Posted: September-12-2018 at 10:32pm |
Zach....Okay, that ballasty thing. Is that the ceramic block that has the two wires attached to it? I know I have seen it on my other boats. I don't know where its at on this one. So, if it is that ceramicy thing, how do you tell if it is good or bad? |
|
|
|
|
phatsat67
Grand Poobah
Joined: March-13-2006 Location: Indiana Status: Offline Points: 6157 |
Post Options
Thanks(0)
Quote Reply
Posted: September-13-2018 at 10:04am |
|
Dave, if you have a multimeter check the voltage while idling on the input side of the coil.
It should be anywhere from 7-10 volts. If it is getting close to 11-12v then your ballast isn't doing its job. |
|
|
|
|
Post Reply
|
|
Tweet
|
| Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |
Topic Options
davidg wrote: