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Gradual loss of power

S

Seanfish

Member
1994 115 inline 4 (2+2)

Couldnt break 4k RPMS, I had raised the engine WAY up and swapped to a 4 blade, I figured I was grabbing too much air initially. Dropped it back down to eliminate this. I now believe all of this is irrelevant. To verify, I can put the old prop back on and run it, but see below.

Was out Saturday and cant break 36-3700 RPM, boat ran 25-27mph (around 4k rpm) last time out. Started the day at ~23mph. Kept losing power and saw ball sucked in and found the fuel line was kinked. Opened that up, but then only could get 20mph throughout the day around 3500rpm max. This boat should be a 33-35mph boat** (I got 32mph out of it once when I first got it and had throttle left, but scared myself due the way the hull was handling (steering torque tab set incorrectly).

I do have a light ticking noise that has developed as well, so I'm not sure if I have dropped a cylinder, or air leak in my fuel line. My fuel line is short from portable 12gal through water separator to motor, so that will be fully replaced. At the same time I do not want to run it to test if it was simply an air leak if I've dropped/damaged a cylinder and do any more damage than has been done.

Really only 3rd time out since its been to mechanic, but with a 1 year old and 2 other kids, my trips are fairly limited.

What is correct order of troubleshooting here?
 
Been a while, still same issue.

Brand new fuel line, new bulb, water separator.

Finally took it to mechanic, compression is 120s, one float full of fuel, replaced and all carbs cleaned......test tank to 3500rpm and everything ran great (I witnessed this)
Really thought that was going to be it.

Put boat in the water
Around 3500rpm, so far so good.
Hit 3800-4000 and there is nothing further. This is 3/4 throttle.

Shop runs it off their known good fuel tank, so I assumed something with my fuel or tank at this point
Fuel is new - put 1/2gal into a milk jug overnight to rule out fuel & tank -- no debris, no water

I still keep thinking this is a fuel delivery or fuel issue, but could it be electrical?
I have not checked fuel pump (I assume this it was done at mechanic shop). Compression was perfect per mechanic.

There is a ton of knowledge here and I have a pretty good mechanical ability. What are my next steps at this point as affording a mechanic often becomes challenging, and I can do most of this myself....I really just need to locate the actual problem in order to resolve it.
 
At idle pull #1 plug wire off.----Then #2 ----Report result.----Now repeat test at full throttle.----To do this you may have to make up a 6' long test plug wire.
 
If it runs smoothly but is lacking in power. you might try a prop with a couple of inches of less pitch.

jeff
 
fastjeff said:
If it runs smoothly but is lacking in power. you might try a prop with a couple of inches of less pitch.

jeff
Click to expand...

Definitely not a prop issue. I had 3800 MAX, but motor was running properly -- was a a 26p laser II prop which was just too much for the motor/boat combo and way too much torque to the helm to the point of dangerous.

Dropped to an aluminum 4 blade 21 pitch which is where I *THINK* I need to be (single engine cat, looking for cruise economy and load capacity, max speed is not my end goal). Never been able to test WOT since I cant get there. This one is NOT a prop issue and I'm not trying to mask the problem by increasing/decreasing what I believe is the correct prop for my boat.

Lower unit had shift cam break, replaced that, one good trip, and then this current issue presented.

I did take a couple pics last night. I see one plug wire was crushed by mechanic putting the cowling back on, and a ton of corrosion on my lower coils. Figure trained eyes may see low hanging fruit so here they are.
 
Figured I’d post an update on the power loss issue. Finally located a hidden air leak in a fuel line after unable to hold idle (I ran it about 1x monthly in my driveway) without fast idle to 1500 or so.

Havent dropped it to test, but changed that line and motor now holds 1200rpm without fast idle on muffs which I was unable to do previously. No trying to die out or anything, I’m fairly confident this was the issue. Will confirm within 1-2 weeks.
 
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