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Author Topic:   Throttle Hard To Control

Drmorison posted 06-27-2014 04:58 PM ET (US)
I have a 1993 SPORT 13 with a Johnson 40-HP Tracker of the same year. I am having trouble with the throttle control. There are two problems. It seems to speed up on its own. If I am cruising at a certain speed, the boat will go along fine for a while, and then it will start gaining speed pretty quickly until I throttle back. But then, instead of going back to where it was, it slows WAAAAY down and I have to throttle back up again.
The second problem is related. It seems like as I push the throttle forward, I don't get a smooth increase in speed. I get a very small increase in speed, and then all the power comes in at once and I immediately have to throttle back down again. Is this normal? Is this a sign of a problem? Any ideas?
contender posted 06-27-2014 09:02 PM ET (US)
Carburetor problems. But I would ckeck your primer bulb first. And the friction screw on the controler could be tightened.
jimh posted 06-28-2014 03:03 AM ET (US)
Moved to REPAIRS/MODS.
jimh posted 06-28-2014 03:05 AM ET (US)
With some boats and certain combinations of engine and propeller, the throttle can be rather touchy about holding a steady engine speed due to the load on the engine changing very rapidly with boat speed. When the boat starts to fall off plane, the load on the engine increases rapidly, and typically the engine speed will drop way off at a constant throttle setting.
macfam posted 06-29-2014 07:22 AM ET (US)
I was plaged with the same problem with a 2000 Johnson 40 on our 13 Super Sport. Frustrating!
It seemed never happy....... Falling off plane, or then picking up and revving faster than I wanted to go. Switching to a slightly lower pitch helped somewhat, and so did a hydrofoil (Doel-fin, or Sting-Ray Jr.)
When I repowered with a 30 E-TEC, the problem basically disappeared.
I'm crediting the computer controlled aspect of the E-TEC that keeps the rpm's very constant.
We have a 13" SST prop, and still have the hydrofoil. This boat acts like a different boat. Far, far easier to control speed and planing.
We lost very little top end speed. Maybe 2-3 mph, and gained a ton.
No smoke, sips fuel, quieter, and starts instantly no matter how long sitting dormant.
If you ever consider repowering, take a serious look at the 30 E-TEC. It is a perfect match.
Phil T posted 06-29-2014 11:19 AM ET (US)
As Contender said -
Check the shifter control box and linkage in the engine. Check for worn parts.
If the throttle increases on its own, the friction adjustment needs to be increased.
Clean/Rebuild the carbs.
You should also review the engine height and prop for appropriateness.
You need to have the appropriate setup for the boat/engine/load and conditions.
GRAND NUSSIE posted 06-29-2014 07:24 PM ET (US)
I'm going to side with Jimh on this one. Some boats just don't want to run at certain speeds, especially tail heavy ones, and will cause these speed changes.
Dick

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Author	Topic: Throttle Hard To Control
Drmorison	posted 06-27-2014 04:58 PM ET (US) I have a 1993 SPORT 13 with a Johnson 40-HP Tracker of the same year. I am having trouble with the throttle control. There are two problems. It seems to speed up on its own. If I am cruising at a certain speed, the boat will go along fine for a while, and then it will start gaining speed pretty quickly until I throttle back. But then, instead of going back to where it was, it slows WAAAAY down and I have to throttle back up again. The second problem is related. It seems like as I push the throttle forward, I don't get a smooth increase in speed. I get a very small increase in speed, and then all the power comes in at once and I immediately have to throttle back down again. Is this normal? Is this a sign of a problem? Any ideas?
contender	posted 06-27-2014 09:02 PM ET (US) Carburetor problems. But I would ckeck your primer bulb first. And the friction screw on the controler could be tightened.
jimh	posted 06-28-2014 03:03 AM ET (US) Moved to REPAIRS/MODS.
jimh	posted 06-28-2014 03:05 AM ET (US) With some boats and certain combinations of engine and propeller, the throttle can be rather touchy about holding a steady engine speed due to the load on the engine changing very rapidly with boat speed. When the boat starts to fall off plane, the load on the engine increases rapidly, and typically the engine speed will drop way off at a constant throttle setting.
macfam	posted 06-29-2014 07:22 AM ET (US) I was plaged with the same problem with a 2000 Johnson 40 on our 13 Super Sport. Frustrating! It seemed never happy....... Falling off plane, or then picking up and revving faster than I wanted to go. Switching to a slightly lower pitch helped somewhat, and so did a hydrofoil (Doel-fin, or Sting-Ray Jr.) When I repowered with a 30 E-TEC, the problem basically disappeared. I'm crediting the computer controlled aspect of the E-TEC that keeps the rpm's very constant. We have a 13" SST prop, and still have the hydrofoil. This boat acts like a different boat. Far, far easier to control speed and planing. We lost very little top end speed. Maybe 2-3 mph, and gained a ton. No smoke, sips fuel, quieter, and starts instantly no matter how long sitting dormant. If you ever consider repowering, take a serious look at the 30 E-TEC. It is a perfect match.
Phil T	posted 06-29-2014 11:19 AM ET (US) As Contender said - Check the shifter control box and linkage in the engine. Check for worn parts. If the throttle increases on its own, the friction adjustment needs to be increased. Clean/Rebuild the carbs. You should also review the engine height and prop for appropriateness. You need to have the appropriate setup for the boat/engine/load and conditions.
GRAND NUSSIE	posted 06-29-2014 07:24 PM ET (US) I'm going to side with Jimh on this one. Some boats just don't want to run at certain speeds, especially tail heavy ones, and will cause these speed changes. Dick