3/4 throttle

[Michael Gegoski]

I have a 1436 tracker topper with a 15 hp mercury and when I throttle up between 3/4 and full there seems to be no difference in speed. I tried to adjust the trim but it makes no difference. I go fishing with my son who weighs about 200 lbs and I'm at 135 lbs. The front deck is made of 2x4s and 3/4in plywood and I'm in the process of using 1/16 aluminum and 1/2 in plywood. I have a trolling motor up front and a electric boat anchor. Gas tank and battery is in the back of the boat. Any suggestions on what I could do would be much appreciated. Thanks in advance.

 

[flatheadsteve]

I have a 1436 tracker topper with a 15 hp mercury and when I throttle up between 3/4 and full there seems to be no difference in speed. I tried to adjust the trim but it makes no difference. I go fishing with my son who weighs about 200 lbs and I'm at 135 lbs. The front deck is made of 2x4s and 3/4in plywood and I'm in the process of using 1/16 aluminum and 1/2 in plywood. I have a trolling motor up front and a electric boat anchor. Gas tank and battery is in the back of the boat. Any suggestions on what I could do would be much appreciated. Thanks in advance.

First get a tiny tach and find what rpm your topping out at. Sounds like you probably have too big of a prop but without knowing what rpm your turning its just guesswork. Once you know your rpm there is a simple formula for finding the right size prop from there.

 

[Michael Gegoski]

First get a tiny tach and find what rpm your topping out at. Sounds like you probably have too big of a prop but without knowing what rpm your turning its just guesswork. Once you know your rpm there is a simple formula for finding the right size prop from there.

May I ask what is the formula, and what kind of tach.

 

[flatheadsteve]

May I ask what is the formula, and what kind of tach.

Lowering the prop pitch 1 inch will increase 200rpm. Raising it will do the opposite. Find out what your recommended max rpm for your outboard is and you can go from there. There are a lot of manufacturers of small tachometers on Amazon. Very simple install and well worth the $15 or so just to keep an eye on engine hrs.

 

[thill]

Question: Does the engine RPM stay the same or do the RPM's go up?

Your throttle cables might need adjusting.

I once had a prop that was slipping on the hub that did the same thing.

 

[LaqueRatt]

Is it a long shaft or short shaft?

 

[Michael Gegoski]

Is it a long shaft or short shaft?

It's a short shaft

 

[Michael Gegoski]

Question: Does the engine RPM stay the same or do the RPM's go up?

Your throttle cables might need adjusting.

I once had a prop that was slipping on the hub that did the same thing.

The rpm's stay the same. How is it possible that the cable needs to be adjusted?

 

[Michael Gegoski]

Lowering the prop pitch 1 inch will increase 200rpm. Raising it will do the opposite. Find out what your recommended max rpm for your outboard is and you can go from there. There are a lot of manufacturers of small tachometers on Amazon. Very simple install and well worth the $15 or so just to keep an eye on engine hrs.View attachment 115576

Thanks, I'll look into it

 

[airshot]

With the engine not running, look into the carb and see if the throttle is wide open at 3\4 and full. You shoukd see some difference in the butterfly opening between 3\4 and full open. This might be where a cable/linkage adjustment might be needed. If the engine is running at peak performance, then you adjust the prop pitch choice to allow your engine to reach max wot.

 

[Michael Gegoski]

With the engine not running, look into the carb and see if the throttle is wide open at 3\4 and full. You shoukd see some difference in the butterfly opening between 3\4 and full open. This might be where a cable/linkage adjustment might be needed. If the engine is running at peak performance, then you adjust the prop pitch choice to allow your engine to reach max wot.

Thanks airshot I'll look into it.

 

[thill]

The rpm's stay the same. How is it possible that the cable needs to be adjusted?

Because, if adjusted wrong, you may be at full throttle when the handle seems like it is only at 3/4 throttle.

With the engine not running, look into the carb and see if the throttle is wide open at 3\4 and full. You shoukd see some difference in the butterfly opening between 3\4 and full open. This might be where a cable/linkage adjustment might be needed. If the engine is running at peak performance, then you adjust the prop pitch choice to allow your engine to reach max wot.

^^^This^^^

 

[Michael Gegoski]

Because, if adjusted wrong, you may be at full throttle when the handle seems like it is only at 3/4 throttle.



^^^This^^^

Thanks, I'll look into it.