Johnson performance

jasoncooperpcola · #1 07-23-2011, 08:39 PM

I took my V20 out today for the first time since may. Engine is a 1985 Johnson 150, Top speed was exactly 30.0 mph at 4500 rpm with the engine trimmed all the way up. I ran a 6 gallon tank of gas/oil and a full can of seafoam till it got to low to run.

On that six gallon tank with about an inch of gas left in the bottom (maybe a gallon?) i got about 6 miles. I should get better mileage than that, right?

My only other concern was the top end rpm of 4500 rpm. I read on the prop that its a 15 1/2 x 14. It seams i have a "dead spot" in the throttle from after it engages in gear to about 9 1/2 o'clock. Is this normal?

Other than that she is very strong and ran good. No electrical problems with the motor.

THEFERMANATOR · #2 07-23-2011, 09:14 PM

How are the carbs? When was the last link and sync done? Are you sure your getting full throttle? Your milage sounds a bit low, but the 150 cross-flow is a THIRSTY pig(espescially if it isn't propped right).

jasoncooperpcola · #3 07-24-2011, 08:29 AM

Not too sure on the carbs. It fires right up so i would think they aint too bad.
I don't even know what link and sync is

. Is that the carb linkage?
I had the throttle pushed down as far as it would go. What else is there to check?

Also, after the first run i took the doel-fins off the cavitation plate, only difference i noticed was it was a little more stable in turns with the fins on, otherwise i noticed no difference.

jasoncooperpcola · #4 07-24-2011, 08:37 AM

Also i found and OMC stainless prop 15x17 for $40. Is that too much prop?

THEFERMANATOR · #5 07-24-2011, 10:03 AM

Quote:

Originally Posted by jasoncooperpcola

Also i found and OMC stainless prop 15x17 for $40. Is that too much prop?

It should be worth a try. The link and sync is the carbs and timing linkage. If it is off the timing may not go all the way up which will KILL your fuel milage.

jasoncooperpcola · #6 07-24-2011, 10:19 AM

What is required to check the link and sync?
Maybe its time to buy a Seloc manual for this outboard.

I read in another thread a member was having the same issues i am having and everybody said to move to a smaller higher pitched prop.

I just hate to spend money on something that wont help. It wouldn't be so bad if i was working, but right now i am on workers comp and it sucks.

bgreene · #7 07-28-2011, 10:00 AM

Believe you should WOT at about 5,400 rpm and hit high 30's mph if the engine's still making proper hp.

Mulv80 · #8 07-28-2011, 10:24 AM

My 2000 Johnson 150 would run 42 mph at 5500 rpm on my 79' V-20.

THEFERMANATOR · #9 07-28-2011, 10:47 AM

Quote:

Originally Posted by Mulv80

My 2000 Johnson 150 would run 42 mph at 5500 rpm on my 79' V-20.

His old crossflow isn't going to run quite as strong as a newer looper. He should be turning up to about 5300RPM's WOT and I would think high 30's to maybe 40 is possible if all is right with it.

jasoncooperpcola · #10 07-28-2011, 01:23 PM

I am beginning to believe this big *** prop is my trouble. The 15x17 i found for $40 was sold before i could call. Based on what i have read through here i am leaning towards a 14.5x17 prop. Right now i am swinging a 15.5x14 and also have a 15.5x15 aluminum (spare) that does even worse.

I put my throttle wide open, and yes, all carbs are wide open. So my issue is not there i believe. I was able to run it on the hose and use the rest of my sea foam out of my 6 gallon tank that i couldn't use when running.

The previous owners have put some money into this motor. She cranks within two seconds now.

Also what should my compression be?