Plane Problem

[Todd Logan]

My boat is a 2001 Nitro NX750. It had a 75HP Merc on it when I bought it. I always had issues with getting it up on plane, especially with a full live well, more than a 1/4 tank of gas and/or when my buddy's would go fishing with me. I bought a 115 ProXS running a Laser II 22P prop and the difference was night and day. I have been very impressed with the ProXS and have had no issues with getting on plane. This past weekend I went fishing with a buddy of mine, same load as I've always had, no more, no less. However, the motor struggled to get us on plane, to the point my buddy had to move toward the bow to help out. Trimmed all the way down, the stern would just dig in and wouldn't plane out . Once on plane it it ran like a bat out of hell. Any ideas on what's going on before I spend money to have the dealer look at it? :unsure:



Many thanks in advance!!!!

 

[Josh Petty]

What were your top RPMS once it broke over? Could be you dropped a coil

 

[Marty Klein]

My 2001 has a 2002 90 big mo. I have always had the same problem as your experience when I trim all the way down as many folks suggest. I simply believe that the 90 is too little a mo for a "floor it Myrtle" takeoff.

 

[TOMMY RICH]

Don't know how heavy the 750 is but, my tin 185 jumps up on plane so fast it'll make ya' head spin with a 90.

 

[Bob Bourget2]

I'd like a bit more info...

-Did it only happen once?

-We are experiencing "vapor lock" issues. You MUST squeeze primer bulb before EVERY start.

 

[Todd Logan]

pettymsj - I didn't notice the RPM once it finally broke plane, but in the past it's been

around 4k until it digs out then jumps up and I back off the throttle and cruise between 4500-5200 RPM



Bob B. - It happened almost every takeoff over the 3 days. I never just crank and go, even though it's summer, I still allow it to idle 30-60 seconds before. As far as the primer bulb is concerned, I normally do prime it, but I cannot remember if I did the the first day, but definately didn't the last two. It ususally fires right up once I prime it the 1st use after a long sit in the garage.



FYI - I reallty do LOVE :wub: this motor!!!! Since Oct. this is the first issue I've had with it and I hope it is just something stupid like the Primer Bulb :wacko:.

 

[Darryl Stafford]

 

[Bob Bourget2]

Let's eliminate the easy stuff first...try squeezing the bulb 'till firm before every launch....let us know the outcome...

 

[tightline 700lx]

Don't know if it helps but I have a 2001 700lx (almost identical boat) with a new 115HP optimax and there is a huge difference between planing speed of my boat with a full tank and livewell vs a half a tank and full livewell. I have a 24v trolling motor and had to move the batteries to the front under the front fishing seat. Havent had any problems since then.



some info that also might be helpfull, jackplate or not? did you remove and plugs on your laser? etc.

 

[Mark Jaworski]

No expert here, I had the problem with a 150 Opti on one of my previous boats. Boat was great for 2 years then all of a suden plane problems. Turned out to be a bad coil.

 

[joseph currier]

a littel advise to those with minor opinions.

ONCE BOB B. GETS INVOLED WITH A DIAGNOSES step aside and dont confuse the issue you added posts that only muddle the waters of what is about to be a very clear picture.

bob knows what he's doing and asks the poster questions to get to the meat of the issue,

your imput only confuses the poster and bob never gets to help the origanal poster.

we are lucky to have bob b. on this board he is one the most respected athorities on mercury outboards and nitro boats in my neck of the woods and you all would be wise to learn from him.

he and marine usa have been selling and serviceing these brands for many years.

nuff said.

 

[Bob Bourget2]

Any updates?

 

[Todd Logan]

***UPDATE"""



I finally was able to get the boat back on the water. I checked the primer bulb as suggested. cranked her up and let her idle for about 2 minutes then opened her up and she did fine. fished for about 2 hours, checked the primer bulb again, cranked her up and idled her for about 1 minute then took off. This time and each time afterward she would dig in ass first and refuse to get on plane. I tried 5-7 times before I could get her on plane. a couple of times had to walk the steering back and forth to get her on plane. once on plane she runs fine. only noticed two things, one, the water pressure gauge sits at about 20psi on takeoff and two, I can only crank out 3000 RPM when she digs in. Any suggestions???:wacko:

 

[Bob Bourget2]

What kind of maintenance have you done to it and when? How many hours on motor? Does the scenario you outlined happen exactly the same way...in other words....it seems as though it runs well cold, then gives you issues when warm?

 

[Todd Logan]

Haven't had any maintenance on it yet as it was just purchased this past

October. I'd have to guess the hours on it but I'd put it at maybe 5 or 6. I don't

Do a terrible amount of running. And yes, I do believe the scenario to be the

Same each time. Has happened with full livewell and empty. Half tank of gas and

Nearly empty. The first takeoff Of the day is always the best being that it performs

As I expect it to and as it has until recently. So cold takeoff good but then after that

even if it sits for a 1 or 2 after fishing, it just doesn't perform.

 

[Bob Bourget2]

You really don't have any hours on it to speak of. I can say this though....the PCM is calibrated on the rich side for engine break-in, and you are NOT done with that yet. After you reach 20 hours, change the plugs. A quick scan on the CDS wouldn't hurt either, after break-in. I'm leary of suggesting anything "wrong" yet until break-in complete.

 

[Todd Logan]

So should I take her in or should I just Deal with it until I can put more hours on it?