35hp Capabilities

wetwaders · Dec 7, 2006

I took my newly acquired 1976 35hp Johnson out a few weeks ago before it got cold to see how it would do. Started and ran fine but would then cut out under power. If I primed the bulb, it would continue on it's merry way - until I needed to prime the bulb again. Anyway, after getting home found a loose fuel line behind the motor quick-connect that would spew when the bulb was pumped. While on the water my top speed was 7mph with a 15' fiberglass boat. I won't be able to get back on the water until spring. Question is: After repairing the fuel line, would performance pick up to the 15-20mph range I expected or is there a bigger issue I may have to deal with? Thanks in advance for any input!

tashasdaddy · Dec 7, 2006

Re: 35hp Capabilities

it really all depends on the 15' fiberglass boat. there are a lot of styles and weights out there. what is the boat. if unknown, post a picture.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=37;gtid=1179789

when the box appears, backspace the line, to clear, then ctrl v

wetwaders · Dec 7, 2006

Re: 35hp Capabilities

It's 18 degrees outside so pics will have to wait! I can tell you it's an older Kenglass (Bomber style) tri-hull fishing boat with wood/carpet covered deck and platform, fishing seat, trolling motor, etc. My concern arose after a friend said his 14' jonboat w/similar set-up and an even older 25hp g.p.s.'d at almost 20mph!!?? thanks for the reply!

F_R · Dec 7, 2006

Re: 35hp Capabilities

Seven MPH top speed? That sounds totally unreasonable. I'd say something is very wrong with your motor or boat. Or the boat needs a lot more horsepower. It's not even planing is it? I realize that it's like comparing apples to oranges, but my 35 pushes my 14' Lund like the proverbial striped ape.

wetwaders · Dec 7, 2006

Re: 35hp Capabilities

Nope, does not get up on plane. I'm seriously hoping the fuel/air mix is so bad due to the loose hose.

steelespike · Dec 7, 2006

Re: 35hp Capabilities

You certainly had a fuel supply problem when you weren't squeezing the bulb it was probably sucking air through that leak.There is also a good chance it may have been running on one cylinder.Older coils fail pretty regularly on these motors.Find yourself a service manual and go over it until you can get at your motor.If the motor has been sitting a lot it will probably need the fuel system gone through from tank to carb.

steelespike · Dec 7, 2006

Re: 35hp Capabilities

You certainly had a fuel supply problem when you weren't squeezing the bulb it was probably sucking air through that leak.There is also a good chance it may have been running on one cylinder.Older coils fail pretty regularly on these motors.Find yourself a service manual and go over it until you can get at your motor.If the motor has been sitting a lot it will probably need the fuel system gone through from tank to carb.Your motor is rated for about 33 mph in ideal conditions on a light boat.You should be able to do 20 to 25 lightly loaded. and properly set up.

tashasdaddy · Dec 8, 2006

Re: 35hp Capabilities

are you sure your boat is not water logged? check the compression, and spark, using a 10dollars spark tester from auto parts store. the spark should jump about 1/2 inch and be blue. compression should be with in 10% of each other, and preferable above 100psi. post your findings.

wetwaders · Dec 8, 2006

Re: 35hp Capabilities

The boat is dry. I'm hoping for one decent day so I can get on the water and see if the fuel leak was the issue. I am not mechanical at all so I want to cover the obvious for I spend $ for repair. Thanks all who replied! Will post when new info is available.

fireman57 · Dec 8, 2006

Re: 35hp Capabilities

Since everyone else forgot, welcome to iboats. Here in southwestern Indiana it is supposed to be in the 60's next week. You should be able to get out. If your spark is good (and check this first) you may need nothing other than a good carb cleaning. My brother has this exact same engine and it pushes his heavy 14.5 fiberglass boat at about 20-21 with no problem. You may have a bad fuel pump if pumping the bulb solves the problem. Even when you pump the bulb and it sounds like it's running good do you still only go about 7 mph? If you are then I would suspect you are running on one cylinder and the spark test would confirm that. Glad you found your leak. You may want to replace or at least check all the fuel lines on a motor this age especially if they are all original.

wetwaders · Dec 8, 2006

Re: 35hp Capabilities

Thanks, Fireman!
To answer, when it starts to cut out while under power, all i do is give the bulb a sqeeze and it roars back up to 6.8mphd

I am planning on trip out next weekend. We'll see what happens. Are we ruling out the significant gas leak being the main problem?

F_R · Dec 8, 2006

Re: 35hp Capabilities

You have two problems. One is fuel starvation, which could just be the gas leak. The other problem is whatever is causing the lack of power. That is more than likely being caused by running on only one cylinder as has been suggested several times. The one cylinder thing could be caused by a number of things. All anybody can do is guess till some basic troubleshooting is done. Spark test and compression test are the places to start. Don't ignore the possiblity that it's just a spark plug.

Walker · Dec 8, 2006

Re: 35hp Capabilities

Like you say, you've got til spring to get her in top shape. First step would be a compression test. 2nd step would be a spark test. Then I'd go ahead and overhaul the carb/carbs, check fuel pump, and replace all the old fuel lines.

freddyray21 · Dec 8, 2006

Re: 35hp Capabilities

On a 14' Lonestar fiberglass my 35hp Evinrude 1980 vintage would push the boat about 25 mph. It would give a tuber hell, but not get my wife up on ski's. I switched to a 50 hp but the 35 was really all I needed for cruising and tubing.

wetwaders · Feb 22, 2007

Re: 35hp Capabilities

Update: Late Dec. was able to get out with fuel line fixed - managed 8.5mph. Bummed! Finally able to get to the motor last weekend w/neighbor. Spark to both cylinders and compression was 130 & 135. However, we did notice the top cylinder was dry inside and the bottom was "wet." Now I'm guessing carb issue. If agreed, do you think "de-carbing" with any of the cleaners would work or a breakdown and rebuild is in order? Any other suggestions??
Thanks for all the help thus far and sorry for the delay - Jan. weather here was miserable!!

F_R · Feb 22, 2007

Re: 35hp Capabilities

It has only one carburetor feeding both cylinders. It does not make sense that it could only be supplying gas to one of them, so look elsewhere. A broken reed could be a remote possibility, but very rare. A ruptured fuel pump diaphragm will flood one cylinder with too much gas.

You say you have spark on both cylinders. What are you calling "spark" ? Will it jump a 7/16" gap? Jumping the plug gap is not a valid spark test, nor is seeing how high you jump while holding the wire. Hate to keep saying it, but did you try new plugs? Check the simple things first, and don't go tearing into things like the carburetor without good reason.

jimmbo · Feb 22, 2007

Re: 35hp Capabilities

Did you use a spark tester to check for spark? A weak ignition system can quite often jump the .030" gap of the plug with plugs out of the engine and at atmosspheric pressure. Once the plugs are in, the engine is hot, and cylinder pressures are higher, it can't deliver enough voltage to jump even the smallest gap.

Harker · Feb 22, 2007

Re: 35hp Capabilities

When you say "roars" up to 8mph..do you mean the rpms of the motor sounds like it is going fast? If it sounds like the motor is revving up, I bet you have a spun prop bushing or to low of a pitch prop. If it just sounds like the engine is lugging..you need to trouble shoot.

tashasdaddy · Feb 22, 2007

Re: 35hp Capabilities

what do the coils look like? crack or pealing. could cause week spark. you can completely swap the coils, watch where the wires go.. if the wet cylinder follows the coil, the coil not giving adequate spark. by water logged i meant, if it has foam below the floor, that the foam has broken down and absorbed and holding water.

fireman57 · Feb 23, 2007

Re: 35hp Capabilities

If you have the carbs off shine a flashlight in behind them and you will see the reed valves. Looks like a row of shiny flanges. You may have something stuck in there which is easily removed with a needle nose. I'm still betting on spark.

35hp Capabilities

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