Can't get on plane

[Darrenkmac]

I am sometimes having trouble coming up on plane. About 70 percent of my starts during an outing in fact. Sometimes my boat comes up smoothly with no issues. It may not happen again for several trips and then it seems like it can't get past a certain level so to speak. When it occurs though I can start from a idle and give it some throttle and I move forward. I am maxing about 2000 rpm. I may travel 100 yards or as much as 500 yards and then it seems to just take off and run to it's full potential. It is a Johnson Fast Strike 175 and it is pushing a 19 foot Ranger 481 Comanche with tournament gear, myself and my partner. Top speed with that setup is about 55 and unloaded with just me I can get 63 GPS. I was able to have some spare parts so I tried another power pack and optical sensor. Fuel intake cone screen is clean and I changed the fuel bulb too. I tried both Champion and NGK plugs. I have a new set of Autolite plugs but I haven't tried them yet. I am running 87 octane gas but it worked for years with it. Compression is about 100 psi but it was that pressure when it worked properly. Should I be looking at temp sensor maybe. I am missing something. Please help. Thank you for your time.

 

[Darrenkmac]

Forgive me, I neglected to give the year. It is a 94 carbureted engine. I also changed the roller on the throttle advance for the carbs.

 

[oldboat1]

Don't overlook hull condition -- water sloshing around under the floor, or waterl-logged floatation.

 

[Tassie 1]

Read the yellow sticky " Top Secret Files " at the top of this page,
also you should follow basic troublshooting guides,
Don't just replace parts because you've got a spare one in the shed...unless it is definitely faulty.
buy a compression tester and spark tester or make one.

But definitely start with troubleshooting guides, electrical and mechanical.

 

[Darrenkmac]

Thank you Fleet Admiral. As far as I know the hull is ok. It has no leaks at the end of the day. It stays indoors when not in use so it isn't collecting rain water. The slow starts don't always happen. It might take off fine multiple times and then act up. And then run fine again. All in the same day.

Thank you Chief Petty Officer. That is some very good information in those notes and I will begin digging into them. I have the spark tester, fuel pressure gauge and compression gauge and my tests were good. I kind of feel like as I am moving forward on my takeoff that the engine is waiting on something before it revs up beyond the 2000 rpm mark. When I have a proper takeoff, there is no hesitation.

 

[Bosunsmate]

Next time it happens id stop the engine and pull the spark plugs out and have a look at them for any difference

 

[Faztbullet]

Check the high speed jets as they as known to come loose. Will run on top end but feel lazy.

 

[Darrenkmac]

Fished a tournament yesterday and afterwards I pulled the plugs and they were dry. There was fuel oil mix in the front of the carbs where they meet the air intake box. It had dripped out onto the lower part of the cowling cover. Where the float bowl meets the carb it was wet with fuel mix. I could squeeze the flange together and saw slight movement and fuel oozed out. Going to buy new gasket sets for all carbs. Also, when I pumped the bulk I noticed that I could see fuel level inside the cap of the cone shaped inlet filter going into the vro. It is white, but it is transparent enough to see the fuel level. Should I be able to see it ? It I can see the fuel line inside that little intske filter then there must be air in it, right ? The motor worked fine for several takeoffs but mostly it was sluggish until around 2000 rpm. When my boat reached around 8 miles per hour it would takeoff like nothing was wrong with it and it ran great up on plane with plenty of power and acceleration. The bulb never seemed to get tight and stay tight.

 

[Bosunsmate]

it should get tight and hold it for at least a minute with the engine off. Some filters show air some dont

 

[oldboat1]

Place the carb bowl(s) upside down on a piece of glass. Make sure they are not warped.