1991 Cajun Bass boat help plz

[muskiehunter1996]

Ok I have a 1991 14 ft Cajun bass boat with a 1968 55 hp johnson outboard on it. I took it out for the first time yesterday and with just me in it topped out at 22 mph on the GPS which seems a bit slow for this boat and motor. The motor has a 13-3/4"X15 prop on it and I was wondering if thats right for this boat. I didn't have the tach hooked up yet but I do now so next trip I'll see the rpm at WOT. Besides prop is there anything else that might help me raise my top speed? Thanks to anyone who reads this and or provides input.

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

At 22 mph guessing slip of 10% your rpm is about 4100.
Should be about 5500 and the 15" prop is about right.Any number of things could be causing the poor production.
Does the throttle open all the way?Is the motor in excellent tune with good compression?
Is the bottom clean and smooth?
Is the prop in excellent condition?
is the anti vent plate(just above the prop) about even with the bottom of the transom?
Does the boat respond to up trim?
Have the floors been rebuilt or are they spongy?
Is the bottom straight with no bulges or sags?
Has the foam under the floor absorbed water?

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

Yes the throttle opens all the way up the bottom is smooth but a little dirty compression is 115-120 in all three cylinders, new plugs and wires, cleaned carbs runs great. The prop is missing paint but no dings or dents or present. The vent plate is like an inch above the bottom of the boat. When I trimmed it up it went from 21 to 22 mph but i could'nt get anymore than that. the floors and boat shell are all in good condition no water I know of in the boat i dont know anyway of knowing without tearing into the boat though. thanks for feedback steelespike

 

[BobGinCO]

Re: 1991 Cajun Bass boat help plz

Man, that's a tough call. I don't know what the ideal WOT RPM's are on that motor, but if you're substantially under that, you need a lower pitch prop for optimum performance. Not sure what your elevation is above sea level, but that's an issue. I run mostly at 5,000 feet or higher (up to about 9,000 feet), and it means I have to drop a step or two lower in pitch because of my reduced horsepower, caused by my elevation.

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

Ok thanks BobGinCO I looked in the manual and the WOT rpm for the motor is 5000 so when I take it out in a few days I'll see what it's running at. Elevation where is run I'm sure is no more than 500 ft so I dont think it's an issue. The motor does have a hydrofoil stabalizer could that be any issue at all?

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

The foil could cause extra drag if its in the water at speed it also may cause the boat to run too flat with too much boat in the water.
Trimmed right the boat should have 1/3 to 1/2 of the boat in the water.
The 15" prop will only produce about 26 mph at 5000.The rpm should help figure out whats up.
I would think a 14ft bass boat could run more prop. a 17 or 19 perhaps.Do some runs without the foil.
see what we get.

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

The foil could cause extra drag if its in the water at speed it also may cause the boat to run too flat with too much boat in the water.
Trimmed right the boat should have 1/3 to 1/2 of the boat in the water.
The 15" prop will only produce about 26 mph at 5000.The rpm should help figure out whats up.
A further investigation the 15 is really on the low side probably intended for a larger/heavier boat.
I would think a 14ft bass boat could run more prop. a 17 or 19 perhaps.Do some runs without the foil.
see what we get.

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

Ok I took off the hydrofoil so next time out i'll see what i can get out of it at WOT and trimming it. I'm not sure if the tach is right though it sits at a little over 1k at idle and it doesnt go up until about 1/2 throttle and even then it only goes up to like 2k but it sounds like the motor is moving way faster than that is there any way to test it?

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

On the back of the tach there may be a switch note the position and operate it a few times to clean the contacts.
Be sure all the connections are clean and tight. You could get an induction tach like a Tinytach reasonable and easy to install and will work on almost any motor.

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

Ok I looked at the switch and it was on 6 whats the right setting for a 3 cylinder?

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

I'm not sure about the switch except I think the number refers to the number of stator poles.
I believe your motor has 12 poles. I don't know why but I think I read somewhere that position 6 refers to a 12 pole stator.
My information indicates your motor uses a 3 cylinder distributor.It is a capacitor discharge ignition with a list of don'ts when trouble shooting. You might check in the E/J forum for info on the tach setting.
I do wonder if the timing is set right and advancing as it should.

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

Ok i believe your right there are 12 poles so I set the tach to 6 and i took it out today. With no hydrofoil and trimming the motor the most i could get out of it was 24 mph and the tach read 2300 rpm If thats true then I'm probably needing a new prop right?

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz


Here are some pictures of the tach I'm using.

 

[82rude]

Re: 1991 Cajun Bass boat help plz

i had that same motor .on a heavy 16 footer i could get 32 mph if i remember correctly.hub might be spun.thats a looper motor and is great when running correctly and a pita when not.i use to troll 10 hours at a time several days a week with mine and never a hicup out of her.

 

[82rude]

Re: 1991 Cajun Bass boat help plz

check out this site http://www.old-omc.de/index2.html if you have a hard time reading the johnson lit switch to evinrude ,same animal .you might have to navigate the mainpage but you will get there.click 60,s then the year then go from there.

 

[muskiehunter1996]

Re: 1991 Cajun Bass boat help plz

I think I may have found the issue i started pulling plug wires one at a time to see if all the cylinders were running and when I pulled the bottom one nothing happened. I then pulled the spark plug and it was almost completly dry. I then disassembled the bottom carb and it needs a cleaning so once I get some carb cleaner and clean it i'll see how it runs.

 

[steelespike]

Re: 1991 Cajun Bass boat help plz

Sounds like a good find may solve your problem and save the cylinder from self destruction.
If its not getting gas its not getting lubrication.
Your tach isn't accurate prop calculator indicates that 2.42 ratio,15"prop,10% slip 24 mph = about 4500.
If you double the rpm it would be 4600.Maybe a different setting?