boat won't throttle up

[bill_r28]

went to the lake put the boat in the water and idled out then pushed the throttle down and boat died. Started it again did the same thing and repeated the process about 5 times. about the 6th time i hit the throttle and it powered up, but it never did after that. I took it out of the water and hooked a hose up to it sprayed carb cleaner in it ran fine had a good idle. Took it back to the water put it in idled out and did the same thing as before. I had it worked on last summer to replace hose from tank that was leaking fuel into ski well. this is the first time we tried to run it and it wouldn't go. Engine is a 150m hp force 1989 model.

 

[CharlieB]

Re: boat won't throttle up

Starts and idles fine but dies when throttle applied.

a few things immediate come to mind,

1. Partially fouled spark plugs

2. Weak spark

3. Dirty/restrictive main jets in the carb(s)

Remembering the K.I.S.S. principle, start with the easier, more common problems.

Very first thing, check the spark to ensure it is hot enough to carry the load at throttle, then try a new set of plugs before going to the expense of carb kits or expensive ignition parts.

 

[diaric]

Re: boat won't throttle up

if you had it worked on, the idle may be running a little low for putting it in gear without stalling. check under cowl and see if anything got dissconnected.

 

[Tadd_P]

Re: boat won't throttle up

idle is a good scenario here. If ya have a tach you should idle between 600-700 rpm's roughly any lower than that could cause it to die. Too much higher will cause your lower end to clunk into gear and you dont want that

 

[bill_r28]

Re: boat won't throttle up

thanks everyone for answering so fast, i really appreciate your info. Now I have another question, within this same scenario if the boat does not throttle up in the lake water pressure, but it does when hooked to a hose could it be a impellar that needs looking at? I had the carbs cleaned. if all of your ideas don't pan out to be the problem. Is there any other ideas out there from you, our nations best?

T/bill_r28

 

[GiMLit]

Re: boat won't throttle up

K I am a newbie to marine but it is funny I think I can REALLY help you here with this one.

I just purchased a 79 Johnson 75hp Stinger (hehe tilt and trim too) and the guy sold it to me for $200. Said it had a hestiation.
I look over things before I hang it on my Dad's boat found a few small things (cracked hoses etc...) Changed plugs just because and tried it out. Ran like a top. Started first turn each time,idled like it was brand new. Got to the lake took off and was like wow I did AWESOME.

Then periodically, usually while setting up for Wakeboarding vs tubing or whatever idling or shut down during this (hot or cold by the way) and it would fall flat on its face when we tried to take off. I could idle away in gear at a troll but nothing more. I tried a few things and pumping the primer ball like a mad man or high idling it for a minute or two and we would be off and running again.
Anyway long story short fuel pump must have been pulling air and was weak so it had a hard time repriming itself. Idle and starting takes a spit of fuel, open those throttle plates and breath all that air and you need a BIG gulp of fuel and it better not have air in it while the pump is trying to send it.
Fuel pump rebuild kit $20 bucks later and we are ALL good to go.

Give it a shot if you like to test it out. Primer won't just make it go after a few pumps, you are really trying to pressurize the pump chamber to eliminate air so it can do it's job.
At home you have no load so even if you cracked the throttle wide open it takes diddly fuel to make it go. Ignition breakdown won't happen at home either no load no need for large demand, ignition doesn't sound like your issue to me. Compression shows up with a rough idle if it is bad or hard starting. Bad prop - spun woudl show up in the water on take off but engine will rev up and not go and it won't affect it so it stalls etc.....


I say just buy the rebuild kit and change the hoses from inlet to pump and pump to carbs etc....
Hope it works for you as it did me.

 

[diaric]

Re: boat won't throttle up

out of the water, your engine runs about 200 rpm faster with no exhaust backpressure and the prop doesn't have to push against anything (water) when put in gear. its like starting your car in 2nd or 3rd gear with a low idle speed, and it stalls. then jacking the wheels off the ground and putting it in gear and it keeps running. when carbs were done, something might have got knocked loose or idle might need set higher

 

[roscoe]

Re: boat won't throttle up

I concur with GiMLit above, could be fuel pump, or low compression. Could also be a plugged up fuel recirculation system.

The fuel pump rebuild is easy, and I recommend it every 5-7 years.
(if the pumps leaks internally, the fuel ends up in the block and causes a flooded condition.

 

[Lineman052]

Re: boat won't throttle up

I have the same problem with the engine stalling when I put load on it.
It worked before the marina changed the plugs and did a compression test which I only had done as a precautionary measure since I just bought it. The marina told me at the time that it had no compression problems and that the old plugs were badly fouled and were replaced.
I happily headed to the lake and it would stall when I put it in gear. I got towed out and when home I saw that a hose was off, vacuum hose. I fixed that and when back to the lake. Had to row back again. It would not work with a load on but works fine in the driveway.
I took it back to the marina and now they are saying that there was no spark on 2 of the cylinders. I was thinking about putting back the old plugs to see if it went back to the way it was but after reading this post though maybe I should look into the rebuild the fuel pump.