115Hp will not plane boat

[sweaver]

I have listed various questions for this motor and have had little response. I decided to tell the whole story and maybe someone can help. Thsi is a 1992 115Hp V4. It lost compression on one cylinder and was sent out for a rebuild. When it was recieved back from rebuild it was reinstalled. During the breakin period it ran great the first three or four times out. The next time it was run it would not plane the boat unless you moved to the front, let it get on plane and it would run fine. I checked the timing(WOT & Idle),the compression(x2), and each cylinder for spark. Everything appears to be OK. My buddy took the boat out last Saturday and he said it planed out fine each and every time. He did say it sounded like there was a high speed skip from time to time.He also said he noticed when turning to the left the boat appeared to lose power but when turning to the right it dug in and turned great. We took the boat out again on Wednesday and it would not plane the boat. The only thing that had changed is we filled the tank which was half full with gas. Does anyone have any ideas? I have tried everything I know. I actually disconnected the throttle linkage and sat back at the motor to manually try and accelerate but this made no difference. I checked the fuel flow comming out of the carb jets and they all appear to be uniform. When you accelerate it feels like it is on the verge of opening up but it never quite gets there. I thought maybe the prop is slipping but you don't notice any surge in RPM's which I have noticed before when a prop slips. Any help would be greatly appreciated. I just don't understand howw it could run fine the first four or five times and then give this kind of problem.

 

[CATransplant]

Re: 115Hp will not plane boat

You don't say what sort of boat this is on. That's an important part of the equation. <br /><br />Still, if you you have good spark and compression on all cylinders, then I'd be looking at the fuel system. Start by checking the quality of the fuel, then move to all fuel lines, filters, separators, bulb, and anything else in the fuel system. Check for air leaks, partially blocked filters...that sort of thing.<br /><br />Next, move on to the fuel pump. Check flow on that pump.<br /><br />Next would be carbs, but save that for last.<br /><br />One final thing, and this has to do with the boat. Check for water in the hull. A heavy boat will be hard to plane, for sure.

 

[mjash]

Re: 115Hp will not plane boat

What kind of RPM's is it making?

 

[sweaver]

Re: 115Hp will not plane boat

Sorry about that "Cat" the boat is a "19' Nitro fish & Ski. The bilge is dry and I will check fuel lines and filter. The fuel flow appeared to be good coming out of the metering valve in the carbs. I did change the fuel filter before starting the break-in period. The fuel pump is VRO. Thanks for the reply!<br />Mark, I haven't checked the RPM's at WOT but I know it isn't putting out 5000. It is loading up too bad to be taching up that fast.

 

[mjash]

Re: 115Hp will not plane boat

Are you blowing fuel out the exhaust? I just had a similar problem where the timing advance lever was not making it to the stop. Just a thought.

 

[sweaver]

Re: 115Hp will not plane boat

Mark, I didn't notice any excess fuel out of the exhaust. I manually pulled the timing advance lever forward while running and made it to the stop. I could tell the timing was advancing but still not enough power to plane it. Like I said it ran fine the first few times out. It just all of a sudden started this. I'm stumped.

 

[sycamore]

Re: 115Hp will not plane boat

On another post someone pumped the primer bulb while running and got more rpm's, suggesting that he possibly had a fuel problem. You might pump the bulb to see if you can get more out of it when you are at full throttle. You also mention in the original post that you filled your tank which was half full. How much fuel did you add? Twenty gallons is a lot of weight, the extra weight may make a pre-existing problem show up that didn't when the boat was lighter and could build rpm's. Just some ideas.

 

[umblecumbuz]

Re: 115Hp will not plane boat

SF, you said:The only thing that had changed is we filled the tank which was half full with gas.

Are we talking an engine problem here, or are we looking at a boat trim problem?<br />Is the gas tank in the stern of the boat? I suspect so.

 

[sweaver]

Re: 115Hp will not plane boat

Stillfishing,<br />You are correct the tank is behind the row of seats behind the driver. It is narrow and tall and reaches from side to side but this is the same tank that has always been in the boat. If you open the hatch to the bilge you can see the tank looking toward the bow. Trimming could be a problem but this boat never had a problem getting on plane before.

 

[Solittle]

Re: 115Hp will not plane boat

SF174 - Did the rebuild come with a warranty? If so why are you fussing with it?<br /><br />I think CATransplant has it nailed. Were the carbs rebuilt?? If not that would be a must in my book.