Nitro 640 Question

[Jarvis Raynor]

My buddy recently purchased a Nitro 640 lx and has problems getting the boat on plane. The boat has a Mercury four stroke 60hp engine. Initially, when giving it full throttle, the overheating alarm would go off. He took it in to get serviced and had the thermostat replaced. The very next time he went out, the boat would get on plane initially, but as the day progressed, it would do the norm of not putting out enough horsepower to get on plane. After moving at idle speed back to the marina, he purchased and installed a new Interstate cranking battery and the boat ran on plane as it was supposed to. Unfortunately, the very next time out it went back to sub-par performing again. Now he decides that it could possibly be a fuel problem, so he drains the tank and tops it off with premium unleaded. No kidding, the very next time he takes it out again, it will not put out enough horsepower to get on plane, and he is COMPLETELY frustrated at this point. Is there anyone that can give any suggestions that might help my buddy out before he goes broke and insane? My recommendation to him has always been to take it in to get it checked thoroughly, but he is kinda on the stubborn side. Please advise... Any and all suggestions are greatly appreciated.... Thanks..

 

[Scott Hammer TOXIC]

Need engine serial number and year as well as RPM's at full throttle. I can say he needs to start that "checklist" starting with fuel delivery, prop size and type, prop to pad measurement and finally how about a call to the previous owner to see if it was an on-going problem or get some tips on how it performed for him/her? Every boat is different and I had to show the buyer of my 929, her "quirks" for best performance. Have the fuel lines/bulb been replaced? He's got some work to do before the problem can get solved, there's no easy button for boats.



TOXIC

 

[Dan Nevill]

As Toxic said. Your friend needs to check fuel delivery, plugs ect. I have a 640 with a 90 on it and have no problems. Could be an prop issue causing over RPM?I

 

[VA BassBoy1981]

All, this is my boat that is being spoke upon here......I have tried everything I know. I purchased the boat from a Marina that was auctioning it off. They used it for people to rent and just take out. As previously mentioned it did overheat a lot at first and wouldnt get on plane so I took it in and got that issue resolved. Then it would only get on plane the initial launch after that I would only go idle speed on the next start up. At this point I am really frustrated and have put a lot of money into this boat as well as another to get it fixed.



Toxic.....I dont have the serial number on me right now but I will get it to you if that will help. I know the boat will max out at 8000 RPMS. If I have the boat out of the water and hooked up to the dog ears it will reach full RPM's with no problem but put it in the water and it will only get to 3000-3500 RPMS.



I havent checked the fuel lines or anything else because it doesnt have any start up problems and the engine is quiet as heck. Sometimes I have to turn around to make sure it is still on because you cant hear it.



I dropped it off at Mare Aquia to have the Mech look it over completly and see if he can figure it out. It doesnt make sense to me.

 

[Scott Hammer TOXIC]

Short of us getting you the answers, Kenny at MARE is a top notch merc mechanic. He will get it running.



TOXIC

 

[Bob Bourget2]

Too much going on. Once your Dealer gets you a prognosis, let us know BEFORE you pick-it up, and exactly what they find.....

In order of a proper triage....

1. Compression test

2. Remote harness hook-up to eliminate boat harness issues {motor isolation}.

3. Fuel delivery and quality. {Remote tank if needed with a known good fuel supply}

4. CDS hook-up, cylinder misfire test. {I conside this THE most valuable, since a non-working cylinder can then be easily diagnosed, electrical and / or fuel.}

If all of the above is done properly...it SHOULD be an easy diagnosis.....

 

[VA BassBoy1981]

Toxic....Yeah Kenny will be working on it. I have quite a little wait as he already has 10 boats ahead of me. It runs great, it just doesnt get on plane after the initial launch.



Bob....I also have him giving it a complete look over including wiring, fuses and power issues that he may find i.e. lights, horn, anything I didnt think to check. Oh BTW Bob, all of that stuff you were talking about, I am completely clueless and I hope Kenny knows what this means.



I will let you all know the minute I hear back from Kenny.

 

[Scott Hammer TOXIC]

Kenny put a "tune" on my 2000, 225 efi that made it come alive. I have no idea what he did but it was a different motor when he got done with it. He did it as a favor because we had a hard time locating a saddle tank leak. Turned out the tank had a hairline crack in the back and would let the saddle tank lose pressure. His father is/was a mechanic for Merc's Racing team. Tell him Hammer says hey!!



TOXIC

 

[VA BassBoy1981]

Toxic.....I will relay the message. I am still praying its something minor!

 

[VA BassBoy1981]

First diagnosis was a coil, Mercury covered it because it was still under warranty. Kenny called and said the boat was ready and everything was good. I then picked it up and took it out on Sunday that just passed. Guess what????? Still the same problem!!!!!



I took it right back and dropped it off, I am supposed to pick it up today and hopefully its fixed. Im starting to think I was sold an egg!!!!:angry::angry::angry:

 

[VA BassBoy1981]

Everyone, I finally got the problem!!!!!!! You will guess what it was....Well it was the prop!!!! Even though the thermostat and coil needed to be replaced but the prop was too big. I guess the marina I purchased the boat from changed the prop to sell it and didnt know the prop they put on it was too big. Well I put the right prop on it and she runs like a champ!!!!!!!

 

[Mike H]

What was the right prop? Size? Pitch?