High Thrust props on non high thrust kickers......

[Dave S]

Just wanted to report my results on this. I had issues with my kicker needed higher rpm's in order to troll my boat, which caused excess noise and vibration, so, after speaking with Chris at Forsch Marine, I decided to throw on a high thrust prop to see what it would do. I have a tiller model Yamaha 8hp (non high thrust) and the prop I went with was a 9" dia and 5" pitch 3 blade. What a difference it made. Rarely need to go past 1/4 throttle to get my 16' Arima to trolling speeds, with or against the current.

To sum it up, I highly recommend anyone with a regular motor, consider a high thrust prop for trolling purposes. Saves gas, wear on the motor, and keeps the noise down.

 

[GDW]

Do you remember what your new prop cost?

 

[jeffywestcoast]

I was considering this for my new 9.9 Merc. guess I should have just spent the extra couple hundred on the highthrust in the first place

 

[Dave S]

Got mine from Sherwood. Yamaha genuine prop, $150. Used $100 credit I won at banana derby to cover part of it. Well worth the money since it is saving wear on motor, gas and less noise and vibrations.

 

[Fishalot]

Great info. I have same boat and kicker so will be sourcing one for sure.

 

[Fishalot]

Could u post the part number? Thanks.

 

[profisher]

I think you may be wrong about wear on the engine. Yes turning less RPMS so it sounds like it is working less..but you are swinging a larger prop without the benefit of the lower gear ratio that a true high thrust engine uses. That lower gear takes strain off the crank, rods and wrist pins.

 

[ReelSlim]

I think you may be wrong about wear on the engine. Yes turning less RPMS so it sounds like it is working less..but you are swinging a larger prop without the benefit of the lower gear ratio that a true high thrust engine uses. That lower gear takes strain off the crank, rods and wrist pins.

X2....... You may not have any problems depending on the number of hours you put on it though? It's the same as putting big tires on your truck. Sure it works....but you will cut the life of any part that is involved in turning that tire in half.......interesting to see how it holds up?

 

[jeffywestcoast]

ya I did some reading and I am not changing, unless I get the whole new lower unit.. no point in trying to make parts fail prematurely.. it's not like I have to rev it up much to get to trolling speed.. pretty happy just how it is.

 

[Bait&Sea]

Just wanted to report my results on this. I had issues with my kicker needed higher rpm's in order to troll my boat, which caused excess noise and vibration, so, after speaking with Chris at Forsch Marine, I decided to throw on a high thrust prop to see what it would do. I have a tiller model Yamaha 8hp (non high thrust) and the prop I went with was a 9" dia and 5" pitch 3 blade. What a difference it made. Rarely need to go past 1/4 throttle to get my 16' Arima to trolling speeds, with or against the current.

To sum it up, I highly recommend anyone with a regular motor, consider a high thrust prop for trolling purposes. Saves gas, wear on the motor, and keeps the noise down.

Good info, I am currently mounting an early 9.9bigfoot on my 18'. It has the same prop you describe 9 x 5, 3 blade. Cause it is not an electric start it only has 5amp alternator and my worry is I wont use enough RPM on the kicker to get a decent charge output to run my HP riggers and electronics. I have a solid electrical system to start but it is in the back of my mind.

 

[trendsetter]

X2....... You may not have any problems depending on the number of hours you put on it though? It's the same as putting big tires on your truck. Sure it works....but you will cut the life of any part that is involved in turning that tire in half.......interesting to see how it holds up?

Actually it's the opposite. A lower pitched, "high-thrust" prop would be like putting smaller tires on your truck. Or like changing your gear ratio in the rear end to provide more power at the low end.

The new prop is probably gripping the water better and losing less energy to slip. If it is lower pitch than the original prop then it would in fact be putting less strain on the engine while improving efficiency at the same time.

 

[ReelSlim]

Yes...... If the pitch is lower. That however was not mentioned just the size of the prop so I assumed it was the same pitch and a larger prop....me bad.

 

[Dave S]

Yes...... If the pitch is lower. That however was not mentioned just the size of the prop so I assumed it was the same pitch and a larger prop....me bad.

original prop was a 8.5 dia and 7.5 pitch. New "high thrust" prop is a 9 dia and 5 pitch.

 

[Dave S]

Also, spoke to mechanic at sg power today. He says it will be hard on the motor at the higher throttle positions. Won't allow the motor to hit its max rpms and would be working the motor too hard. He says its not an issue at lower throttle position/rpms. I don't log big numbers on my kicker so I'm still happy with this set up. Won't serve me well as an emergency back up so I think I'll keep the other prop on board as a spare if needed. Thanks for mentioning this Rollie.

 

[Canso]

It's not the pitch, it the large ears giving more traction, Less slippage.

 

[ReelSlim]

Also, spoke to mechanic at sg power today. He says it will be hard on the motor at the higher throttle positions. Won't allow the motor to hit its max rpms and would be working the motor too hard. He says its not an issue at lower throttle position/rpms. I don't log big numbers on my kicker so I'm still happy with this set up. Won't serve me well as an emergency back up so I think I'll keep the other prop on board as a spare if needed. Thanks for mentioning this Rollie.

Thanks for the update Dave. Also good that your mechanic was up front with all the information about the mod. Like I said earlier......most guys don't put enough hours on any of their toys to wear them out even without making any mods to them unfortunately Definitely worth trying it out especially since it seems to have fixed any complaints you had with how it was before. And for the record I'm all for making tweeks to my set ups......just good to know the pros and cons. Keep us posted how it does this season......cheers!

 

[SpringVelocity]

I guess this is good to do but wouldn't do it in the warranty period that is all. Doubt Yamaha would back it. I have the T8 model and I picked it specifically this reason. I used to run same size boat with it.

 

[GDW]

Dave in an emergency situation where say your main dies on the water can you really see yourself trying to change the prop out at sea? Better off to come in slow with whatever prop you have installed if your worried about the engine.

Keeping a spare in the boat is deffinetly smart but not necessarily for an on the water situation unless you absolutely had to change it.

 

[trendsetter]

Also, spoke to mechanic at sg power today. He says it will be hard on the motor at the higher throttle positions. Won't allow the motor to hit its max rpms and would be working the motor too hard. He says its not an issue at lower throttle position/rpms. I don't log big numbers on my kicker so I'm still happy with this set up. Won't serve me well as an emergency back up so I think I'll keep the other prop on board as a spare if needed. Thanks for mentioning this Rollie.

I'm surprised that the mechanic would say that, it's pure speculation on his part. It's far more likely that the new prop WILL allow the motor to reach it's recommended max RPM range. A 2.5" reduction in pitch will have a far greater effect than the increase in diameter.


If you really want to know then the test is simple.

1. Look up the recommended maximum RPM for your motor.
2. Hook up a tach to the kicker.
3. On the water, put the kicker in FWD and observe the RPMs at Full Throttle.

If the motor reaches it's maximum recommended RPM range then the prop is not negatively affecting the powerhead. If it does not reach the maximum recommended RPM range than yes it is putting additional strain on the engine which could lead to premature wear.

I'd wager your new 5" pitch prop will allow the engine to run at a higher RPM than the original 7.5" prop. The only way to know for sure is to test yourself.

 

[Birdsnest]

Im with trendsetter on his comments. High thrust prop makes the motor push more like a tug boat. Slow and strong. Or like a bike in low gear going up a hill. This is better for a trolling motor for the prop will have more traction/thrust at lower speeds and have a better response for situations like trolling into the wind. It certainly will not be harder on the motor tho it will not be very efficient at higher RPM anyhow.