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dflynnatc

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In the process of refurb on 57 Lonestar Malibu and 1960 40HP Johnson Super SeaHorse. We've replaced just about every piece of rubber or gasket as well as rebuilt carb. Engine starts and runs well, we think we have carb dialed in, so migrated out of the barrel to the river. Some trial and error there. Solved spun prop situation. BUT, the fastest we got the boat to go was 10mph (iphone/gps). Normally around 7-8 mph. Engine seemed to be humming away and sounded great. Soooooo...Question... 14' Lonestar Aluminum boat..with 40HP engine should be making what speed? (Boat is rated for a 35, but PO moved station forward to accommodate heavier engine) Engine sounds great, starts, runs, high circuit seems correct. Any assistance would be helpful. Getting full throttle, roller cam adjusted, butterfly is wide open, armeture plate advances to what we believe is full position. Planning on putting a tach on it to find our rpms, but at this point, were dumbfounded. Should be getting 20-30 mph easy... yes?
 
Unless you and a buddy were on it and each weighed 450 lbs. then yes it should be going faster.
What speed did it feel like? What does the whole setup weigh?
Do you think that IPhone GPS is accurate?
What prop is on there? Dia and pitch?
Is the prop below the transom?
 
nope... 460 for the both of us. Brochure says boat weighs 325. Engine was 139 I believe. Thats 924lbs for set up and us. Prop is 10 3/8 x 14. GPS has been dead on in the car when compared to the speedo. Speed felt slow. Below transom.
 
Sure you don't have another spun prop..??? My 58 35 'Rude pushes about the same weight boat (16' aluminium) at about 25-28 mph (guess, not GPS), with the same prop. Check the revs with a tach. But, if it sounds good, there has to be slippage somewhere. Either in the prop, or around the prop. When you are in the boat, is the prop still in the water? You aren't putting too much weight forward? My boats empty, with tiller steering, a 70lb truck battery in the bow, fuel tank about 3' forward of the transom. I'm 150, at the very back. Boat balances great, handles great.
 
Was thinking the same thing, but after trip and while on trailer, I put engine in gear and couldn't spin the prop...only rotated the motor/flywheel. So not thinking it,too,is spun. Not convinced it is exactly the right prop because i bought it on ebay after I was striking out here and trying to find a "new" prop. This is a remote set up with me at 4' from the bow @ 230. Prop is definitely in water, and I believe we have engine pitch correct and weight distributed appropriately. Will update when I get the tach on it. Curious... is there a way to ( i know this sounds weird) tach the prop?
 
I had the same problem with my 55HP Johnson, rebuild the carbs & could not get top in speed, I can not tell you how to do it, but the carbs may need to be synchrontized (spell may be wrong)
That was my problem, 16 MPH with a 55 Hp on a 16' Alum boat, after fixed 42 MPH, but I paid to have it done
 
Interesting that it had that level of reduction. I only have 1 carb, so I don't think that's my agg, but that level of impact is impressive. We've been wondering about the reeds and if/how they could much impact they may have.
 
Not that I know of..taching the prop. I don't know, but it sounds like you have too much weight too far forward. When you get moving, not enough prop in the water. When you turn, does the engine rev higher? At that speed, if the engine revs up on a turn, you are not getting enough bite. With roughly the same weight boat, I've got about 320 at the stern (me, motor, gas tank), and about 60-70 bow weight (battery). I ran a bit of a different set up with a newer 20hp merc, me, motor, small battery, tank at stern, no bow weight, and got about 35 out of it, and wow, what a hairy ride. Have a look at how mine sits at rest. How does it compare to yours? I'd try shifting some weight towards the rear, see what happens.
IMG_0531.jpg
 
And you do have a different prop than me. I've got a 10 3/8 X 12. Yours should give you a higher top end.
 
First thing you need to check....... are you running on all cylinder's? An outboard will run on one cylinder and "sound " smooth and run great but have no power.

I would use a timing light to verify the spark.

I am almost positive your motor is also designed to run on 24:1 gas/oil ratio.
 
Good point...could also just pull plugs...look for a wet one after running wide open. And yeah, 24:1 was spec'd for the older motors. But, they are all bearing motors at that hp. With the new oils, and all bearings, you can run up to 50:1. I do on all my old stuff, except for the 5 1/2 I've got, it stays at 24:1 because its got bushings, not bearings on the crank and rods.
 
After the motor has run at full throttle for a few minutes, shut it down and use your hand to feel for the cylinder head temperatures being equal on both cylinders...it sure sounds like it may be running on only one cylinder...that boat should do at least 30mph with that motor running properly.
 
We know we have spark in both spark plugs, but we _don't know_ if is firing. Top plug dry and appropriately colored for firing plug, bottom comes out wet. We were operating with the notion that it would NOT sound good if it wasn't firing. Friend has a "colortune" plug that we are going to throw in to _see_ if and what color the spark is. That and the Tach will get us closer to understanding.... I assume.

Because we were still unsure about both firing, we have felt the cylinder walls and they appear to have the same warmth to the touch.

You are correct on the 24:1.
 
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If wet is _automatically_ associated with not firing (and we know we have a wet bottom plug) and we know we have spark to the plug and plug is gapped appropriately....can you guys venture a hypothesis on why it isn't firing? Valve not seating correctly? Reeds?
 
A compression test should be done at this point...this will eliminate alot of guessing. Head Gasket? Bad Rings? Scored Cylinder? Crankshaft Seal? As I said the compression test is whats needed first.
 
procured ignition and pressure tester.... would anyone know the pressure I should achieve? also, level of spark that should be achieved?
 
You should have a minimum of 75 lbs psi in the cylinders to run and 125 is nice ;) The key is no more than a 10% variance between the cylinder pressures.

The spark should be bright, crisp and jump a 3/8" gap.
 
Coil is new.... but finished my tests. Both cylinders pump up to 120lbs. Spark is strong, jumps 1/4 in gap in the tester. But......... buddy was on different forum and found in the end of a long thread a post that prompted him to look at the vacuum hose that runs the pump. Which we did. If you pull that hose off the lower cylinder- vaccuum, and pump the fuel line bulb; gas will shoot out the vacuum hose IF there is a diaphragm tear. That is what we found. Took off the fuel pump and there was a tear in the diaphragm. So we will be rebuilding the fuel pump, which to this point we thought was operating correctly.

(just saw the previous 3/8ths post ... we didn't see how far it would jump... just that it crossed the 1/4 in gap... will retest to quantify how far it will jump)
 
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