80hp is only getting 7mph .. too slow any ideas?

[lbcboating]

80hp v4 is only getting about 7mph max on 16ft boat.
At first the motor would only run steady at idle and no more than half throttle. If I gave it more than half throttle it started to choke and die. I later realized the fuel tank was not being vented so I unscrewed the vent bolt and I no longer have that problem. I can give it full throttle without the motor choking or cutting out but the speed doesn't increase. It runs fine. Just far too slow for it's horsepower and weight of the boat.

Compresion = good
Sparks = good

I'm assuming the next step is to check the Carbs? Could this possibly be a dirty fuel filter issue where not enough fuel is getting to the motor? Or something more related to the carbs? Does carb cleaner do well in these situations or should that be avoided with outboards?

Also could it be soiled spark plugs? Or wouldn't I notice more motor sneezing and cutting?

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

What do your spark plugs look like?
How did you check spark?
Check timing if you can
Carb cleaners fine but only when you have the carbs apart and a blowing out all the channels checking that the spray transits through fine.

7mph aint even a drifting barge

 

[EZSteury]

Re: 80hp is only getting 7mph .. too slow any ideas?

I'm no expert but if You have full throttle and rpms and it doesn't move faster than 7mph I would look behind the motor see if the turbine is moving as fast as the motor flywheel, then something obstructing under the boat. Just My .2c .

 

[82rude]

Re: 80hp is only getting 7mph .. too slow any ideas?

if you rpms increase when you give it throttle but you don't go anywhere look to your prop.if its a pin drive the shear pin might be broken or the hub is spun.no-pin drive its the hub.

 

[boobie]

Re: 80hp is only getting 7mph .. too slow any ideas?

Is it running on all 4 cyl and not just 1 ???

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

I cannot tell if it is running at full RPMS because based on what I can hear the RPMS don't really increase , unless it's already at full RPMS .. I've never heard this motor at full RPMS i just got it so i'm kind of learning about it still.. When I do give it full gas it sounds strong but it should sound stronger for an 80HP.. that's my conclusion. So i'm assuming it might be a fuel/carb related issue but i'll check the prop .. but first what is the prop and where should I be looking for this pin?

Also yep it's running on all 4 cyl i checked and confirmed

thanks

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

i found the prop and pin actually i'm checking that as well but that seems to be fine also

 

[Pink Shibi]

Re: 80hp is only getting 7mph .. too slow any ideas?

lbcboating, i have a 17'3" boat that weighs around 3500 lbs with a 90 hp 2 stroke and a 3 blade propat 17 degrees and i can get it to 28 knots(~32mph). I would say yes there is something definately wrong.

if its not hicupping half the motor may not be getting spark. i am assuming this is an outboard so to check i take the water sheild(air filter looking thing) off and hold my hand in front of(but not completely covering) one of the carb's air intakes. if the motor starts to sputter or die when i get my hand closer to closing off air then that cylinder is firing and has fuel. check each one. if the motor does not sputter and start to die as you slowly cut off air to that cylinder then it is not reciving either fuel or spark. if you do completely cover the carb it will create a vacuum that will suck a LOT of fuel into the carb which will then spill back out. if that happens at least you know you have fuel
if both cylinders one one side or both cylinders on the top or bottom dont affect the engine when you cover them i would check that coil pack it may not be throwing spark or not throwing a hot enough spark. most engines should throw a spark across a 3/8" air gap.

what i find confusing is that you are saying your not getting more rpms at higher throttle. is the connecter from the throttle cable attached to the timing advance and the carb linkage? when you push the throttle forward is it moving the valves in the carbs? is it moving the timing advance? it could be moving the advance without moving the valves in the carbs which would make the engine sound different but not go faster and potentially damage the engine.

ok thats all i can think of. people here could give you better answers if you told them the year make and model # of your engine. i hope this helps.

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

Post a video if you have a camera etc, even if you only run it on muffs in the video.
Keep the lid off the motor for the video and show start up, idle and full throttle, zoom in on your throttle linkages to the carbs too

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

Thanks for the help , i'm going to try doing that one test you mentioned Pink Shibi .. If you get that much speed on your boat with that heavy of a hull it makes me wonder if it actually could be a spark related issued ..

One thing I did notice is that when I fixed the problem with the fuel tank not venting by unscrewing the air vent, it continuously is pushing out fuel through that vent almost like it's an ongoing reservoir for the fuel tank .. is that normal? It's not a lot but it's very consistent. Does this mean the vent is open too much? Before when this vent was closed I could only give the throttle about 50% of gas. If I gave it more than that the motor could choke and die unless I quickly brought it back down to 50% again where it felt like it was receiving gas through the carbs all the sudden.

I do actually think i'm getting more RPM's when I increase the throttle based on what I can hear.. but it sounds like i'm not getting enough. The motor is a 80hp Johnson Seahorse electric V4 .. I believe the year is ~ 1967

I had checked the throttle cable to make sure everything was connected and it looked like it everything was moving properly ..

I'll post a video of the motor on muffs with the shell off the outboard so you guys can see what i'm talking about more clearly

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

Thats not normal with the portable tote tank most people have on their boats.
Is it an inboard or portable tank?

Have you tried pumping the primer bulb while running to see if that helps?

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

Thats not normal with the portable tote tank most people have on their boats.
Is it an inboard or portable tank?

Have you tried pumping the primer bulb while running to see if that helps?

It's a portable tank. One hose goes to the motor, the other hose goes to a vent .. I found it odd that there was consistent flow of gasoline coming from the vent which made me believe there was excessive pressure in the tank likely from a clogged fuel filter or clogged carbs ?

I tried pumping the bulb too while running , had no effect though.

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

Ok, in all the portable tanks ive seen the vent is just a screw cap on the lid, so just the one hose comes out of the tank.

Your vent hose may be working on syphon priniciple. Ie the line to the engine is higher than it so it is syphoning out the vent one as that is at a lower level than the motors pipe

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

If it was syphoning like that the fuel line to the motor may have a lack of pressure, you said you primed the fuel bulb and it didnt help, did it go rock hard?

 

[Bob_VT]

Re: 80hp is only getting 7mph .. too slow any ideas?

Your motor is from the 1960's and we probably need a bit of history on it. Have you ever had it running properly? Are you aware of the last time it ran properly?

The spark needs to be checked on all 4 cylinders. A timing light will help.

When was the last Carburetor rebuild/cleaning?

A 4 cylinder motor will run on only one cylinder which can be very confusing. You are probably running on fewer then 4 cylinders.

Your motor has Points and condensors - have they been checked?

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

thanks . is it possible that the pistons are dirty ?
This boat was sitting for a long time before I got it .. I basically just got it from somebody who had in their family for a long time .. it had been sitting out for along time which is why they sold it. I cleaned it up and got it started back up. I am not sure the last time the carbs were rebuilt or cleaned out .. The guy who sold it from me said he was able to start it up and took it out on the water and it ran great. Which it did when I got it. He said he got a lot of speed on it and it felt like it was MORE than 80hp. Then it sat for another week or so before I picked it up.. So i'm not sure what might have happened in between then .. Is it possible it could be carbon buildup on the pistons? I always throw in 50:1 oil mix.

The gas tank doesn't have a screw to open up a small vent. It does have a screw coming up on a small metal plate that is tightened by a couple small nut bolts which looks more like a connector to the fuel sensor.

If that line is syphoning like that then my first assumption was lack of pressure to the motor , so when i was on the water I had the throttle at both 50% and then at 100%. I applied pressure to the bulb a few times but it had no effect..

bout to post a video ..

 

[Bosunsmate]

Re: 80hp is only getting 7mph .. too slow any ideas?

Ive no idea what that vent is, post a photo of that too if possible.
The primer bulb should go very firm within a couple of primes if you a only running at around 7mph

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

I just noticed that it looks like my throttle cable might not be moving all parts correctly. I posted a video .. I noticed that when I give it full throttle , the smaller lever moves across the triangle metal piece , but doesn't go all the way. It stops where I show it on the video .. I then push the smaller lever up with my finger to demonstrate how far back it looks like it's supposed to go at full throttle. When I do this I notice the flap inside the carb opens all the way. Verses barely half way when I try to accelerate with the throttle 100%.. I can easily adjust the throttle cable to fix this. Unless this is how it's supposed to work? I also notice the actual throttle stops about 75% and I cannot push it anymore which seems like it's just adjusted incorrectly. Unless i'm wrong?

 

[lbcboating]

Re: 80hp is only getting 7mph .. too slow any ideas?

I also posted a video of me revving up the motor on muffs. It does get increasing RPMS (sounds much louder on muffs probably due to less resistance in the water) .. There isn't that much gas in the tank when i'm doing this but I notice that when I put it into gear and then gave it full throttle again the RPMS increased way more. Then again the tank was low.. nonetheless the RPMS seem to be fine , if the motor wasn't getting all 4 sparks i should be able to notice a lot of vibration and shaking on the outboard right?

 

[Bob_VT]

Re: 80hp is only getting 7mph .. too slow any ideas?

Does not sound right at all. I bet it is NOT running on all cylinders. Missing a cylinder or two makes no difference when on land .....it will run and rev up.

If you try to move the throttle...... to see if the carb is opening fully try this. WITHOUT starting the motor..... shift the gearshift into FWD and then try the throttle lever all the way. Moving the linkage will only dump a bit of fuel into the motor but it will do no harm.

Check the sparks with a timing light.........