Performance Question on a 35
 

I recently bought a 35 Lightning.. and have some questions/ concerns on the performance.

I ran it for the first time this past weekend and some of the performance stats seem off to me.

It has 600 SC's, running 28 pitch props. At 4500 RPM's the gauges say that I'm generating 8.5 lbs of boost. This seems way high to me (even running at 4000 ft elevation).

Anyone have any input on this?

Re: Performance Question on a 35
 

Here's what the guages were reading.....

http://www.hotboat.com/image_center/...35HPIM0837.JPG

Re: Performance Question on a 35
 

what was your fuel pressure reading? oil pressure looks a little low for that rpm also, your boat should run in the mid to high 80's and turn up at least 5200 if rev limited.altitude can wreak havoc on your fuel needs and boost was your boat built locally?

Re: Performance Question on a 35
 

your boat/ engine combo you should be turning mid to high 90s if not better at 5200 rpms

Re: Performance Question on a 35
 

600sc in a 35 you should be in the high 90's maybe 100. What year is the boat and single or twin step?

Re: Performance Question on a 35
 

Check out the pic. Single step boat. Newer twin step has curved glass windshield. My guess --- mid/late '90s. Speed likely mid 90's, unless they have been tweeked, which may be the case. I believe boost as stock from Merc would only be 5 -5 1/2 lbs.

Re: Performance Question on a 35
 

Boat is 1995.

Re: Performance Question on a 35
 

Is that the top speed right now? 80 @ 4500?

Re: Performance Question on a 35
 

Looks good. Any more pictures?

Re: Performance Question on a 35
 

Boat was just spooling up in that pic. Still hadn't tweaked the trim. The boost has me worried (8.5 lbs). The fuel pressure was running about 4.5 there.

I'm concerned about the Oil pressure as well. Should be running up in the 50-60 psi range, not 45.

The boat was supposedly built and run for Lake Powell, which is where the pics were taken.

Re: Performance Question on a 35
 

Thanks for spreading that around... Any help or feedback is appreciated

Re: Performance Question on a 35
 

I would be concerned with the boost unless you are running chillers. Some one must have changed the blower pullies. Mine were changed and was near 9 psi. I put stock ones on and did not see much difference. But know the engines will last longer. And I know everyone likes to see 7 to 9 on the fuel pressure . I run 5 all day three years now and no problem. I was concerned with these problems also but if it aint broke , run the hell out of it.

Re: Performance Question on a 35
 

I think you already have it trimmed out enough. The MAX you should trim the boat to is 5 or maybe 5.5. boat is overtrimmed or maybe your indicators are off.

Re: Performance Question on a 35
 

Are the blowers 250s?

Re: Performance Question on a 35
 

for 4500rpms you sure have it trimmed out a lot. 6 is starting to et into the Trailing Mode! :eek:

Re: Performance Question on a 35
 

Stock blower set up on Merc 600 SC's would be the 420's --- not 250's. The 420's would be the B & M mega blowers.

Far as boost --- w/o chillers you are to high for continued running and relialibility, get back to 5 lbs +/-, the change will not effect speed very much at all.

As far as oil pressure --- try changing oil and filter first, be sure you know what you have in the motor to start with, then go from there. 45 psi is not real low for a stock pump, proper oiling is more about volume than pressure.

Couple years ago I looked at a 35 w/600 SC's, owner claimed 100mph but factory test sheet said low/mid 90's.

If you are not comfortable with your own abilities to figure this out get a good, reputable shop to take a look. professional help may not be cheap, but far less expensive than a rebuild if you " run the hell out of it " and break it, that's a real stupid piece of advice.

Re: Performance Question on a 35
 

Could be,, Not sure if the Bmax drives make a difference either,, still in learning mode.

The blowers are 420's,, Motors were evidently set up by a guy named Joey Griffen..

Re: Performance Question on a 35
 

I bet Bravo's would be faster than the B-Max. B-Max are big heavy drives and from what I have heard I know of a race team that tried them back in 2002-2003 and lost MPH by a lot comparded to Bravo's.

Do you have a GPS hand held unit? Also check and see where neutral (level with the bottom) the drives are. Usualy from the factory Fountain set's this up at 3 for the drives and tabs. Take the GPS with you and set up a long long run. Start out at cruise and the drives at neutral and tap them up a half a stop at a time and see where you start to lose speed. Then keep doing this all the way to WOT. IF your drives are neutral at 3 I bet that at 4,000rpm cruise on smooth water you will find that around 4-4.5 will be the best trim and that at WOT anything over 5 to 5.5 you will lose speed.
Remember that the trim button is not the go fast button. Make sure your drives indicator is set properly. From your pic 1 drive is 1/2 a stop higher than the other. Make sure everything is balanced out and accurate.
Have fun and good luck!

Re: Performance Question on a 35
 

The only way you should be getting that much boost (8.5) is if someone changed the pulley size. The upper pulley is easy to measure. Just find out what diameter Merc used and compare to yours. I bet you have smaller pulleys which is fine. Just make sure you run good fuel.
Jackhammer

Re: Performance Question on a 35
 

Is that right? I wasn't aware of that and have been trimming in the same fashion. I was under the impression that as long as you don't trim it up any more than is readable you were ok...

I see your boats on boattrader.com. Looks good!
How is it running? Did you get the bugs worked out?


http://adcache.boattraderonline.com/6/4/2/84845142.htm

can someone tell if there is harm done with over trimming i sometimes bring them up a little extra for the rooster tail when the kids ars tubeing or when i do a drive by.i always thought that as long as you still see it on the indicator you are good.?????????????

Shouldn't hurt anything as long as you have water pressure. Not the most efficient way to run though.

The more you trim the more stress you put on the u jounts.

That is a bad idea - you are totally stressing out the u joints and god forbid they bind, you will blow up the tansom assembly when they come apart and your direction will change from forward to down. Stop doing that.

YEP !!!!!!!!!