Strange Happening 85 HP Johnson

I recently purchased and a 16 foot bassboat with a1978 85 HP Johnson Javelin outboard motor.

The engine istelf appears very clean, to the best of my knowledge it has never been in salt water. I know for a fact that the engine had not been started in nearly a decade, maybe more. Before starting the engine I mixed new gas 50/1 ratio. Replaced the plugs and gapped them properly per the local marine store. Replaced the fuel filter and hooked of the ears to the motor. The first three trips to the lake were great, the forth trip is were the problems started.

1) Boat lost power, even at full throttle I the boat would only rev to about 2500 RPMs

2) Sparatically it would rev up, sometime to 6000 rpms but when it did the boat would go no where.

I took the boat to a local repair shop where they cleaned and readjusted the carbs. Next trip the lake was the same thing.

Other specifics:
19" Pitch prop, lake elevation 1300', 87 octane fuel

Any thoughts on what the problem(s) could be??

Thanks in advance!

Re: Strange Happening 85 HP Johnson

Your fuel pump may not be delivering enough fuel. Try priming the fuel hose bulb when running. That will force fuel around the pump, into the carb bowls. It may pickup and run normally when doing this. If it's as old as you say it is, the bladders inside the pump are probably shot. They were designed to run on leaded fuel from years ago. Today's modern fuels containing alcohol will eat up old fuel system hoses and pumps. Keep an eye on all the fuel hoses under the cowling for softness and leaking.

Re: Strange Happening 85 HP Johnson

Sounds like you have two problems. I cannot relate #1 to #2. As for #1, you have to figure out why it isn't running on all 4 cylinders. Could be several possibilities. The shop should have caught it. Do they stand behind their work?

As for #2, that could be a spun prop hub, or simply cavitation/ventilation (sucking air into the prop stream). Especially on a bass boat. They usually have those motors jacked up as high as they can go without ventilating. Playing with the power trim may help. I assume it has power trim, right?

Re: Strange Happening 85 HP Johnson

emdsapmgr
I tried forcing gas through using the pump but it didn't seem to make a difference. The fuel filter itself is not filled up completely, I wonder if that matters at all?

F_R
I agree completely that the two are not related. Yes, it has power trim and the I was in the process of messing with the trim controls when it did it's little trick. In fact I had a suspition that may be the cause. This is my first boat and I must admit I am not too savy on the ole' trim controls. As far as the shop standing by their work, they sure do, in fact it is on the lake right now and they are testing it. I would like to hear more about this "or simply cavitation/ventilation (sucking air into the prop stream). " as I am new to boating and would like to prevent this from happening if I could.

Thank you both for your input. I will keep you posted.

Re: Strange Happening 85 HP Johnson

Summed up pretty quickly for you here

http://www.boatlicence.au.com/cavitation.htm

Re: Strange Happening 85 HP Johnson

Thanks for the link I appreciate it.

Here is the latest. I took the boat back the shop, they said the timing was off :-( They adjusted it and lake tested the boat. Everything was a go,so when I took it to the lake I was extremely dissapointed when the loss of power happened again, but to a lesser degree. When I got home I noticed my gas tank was crinkled up because I forgot to vent it....AAAARRGGG (I know I deserve spyware sent to me) So I am making a trip out in the a.m. before work with the gas tank valve open to see if that helps. If not back to the shop....Lucky I can see Lake Castaic from my house.

Stay tuned for further updates.

Re: Strange Happening 85 HP Johnson

Good news! Ran the boat with the gas tank vented and it ran like a champ. No hiccups or misses at all. Maybe that was the problem???

Thanks to all who posted your responses!