75 HP Mercury lower unit same as 60 HP Bigfoot Lower unit?

[HSS Heather]

I bought a new 2017 Suntracker 20 ft party barge with a STANDARD 60 hp mercury on it about 1 month ago. Shortly after owning and taking out on the water I noticed a lot of "gurgling noise" from the engine, also losing thrust. Sounded like the engine was partly out of the water. Long story short me and the dealer have been going round and round about whether a 60 hp command thrust would have made a difference. I believe it should be the only Mercury engine on a pontoon, the command thrust part.

He swears he sells tons of regular 60's without any complaints. I get up to about 18 mph at 6000 rpm.

So here is the question, is a 75 hp mercury lower unit the same as a 60 hp big foot lower unit. The dealer is wanting to put a 75 hp lower unit on my engine to "solve" my discontent. He wouldn't put a new engine on the boat since Ive already used it.

He is going to charge me 500 bucks for the new lower unit.

The gear ratio is only 2.07:1 on a 75 hp, but command thrust engines are 2.35-2.38:1.

Help!

[teecro]

Yes the 75 lower end should swap right onto your little 60...

500.00 is about spot on for what you would have paid had you purchased the 60CT originally... Not to side with the dealer but he is correct in that Sun-Tracker will indeed equip these pontoons with even smaller motors for low price point and that many little lakes have HP limits.... But truthfully 18 is about spot on for speed as I had the 60CT on an 18-footer and that was generally about all she was good for... Thus after the lesson I learned if I were buying a your boat today it would have to have max nameplate HP by way of the 90CT

[HSS Heather]

Okay thank you for your input! So will the 75 hp engine lower unit be the same as a 60 hp big foot lower unit? Or do the 60 hp big foot lower units use the 90 and up command thrust lower unit?

Did you experience any of that prop trouble I'm experiencing with loss of power?

[teecro]

Okay thank you for your input! So will the 75 hp engine lower unit be the same as a 60 hp big foot lower unit? Or do the 60 hp big foot lower units use the 90 and up command thrust lower unit?

Did you experience any of that prop trouble I'm experiencing with loss of power?

The 60CT uses the 75/90 lower housing allowing it to swing a 14" prop and the 90/115CT uses the 150 lower housing allowing for a 15" (?) prop....

You would need to explain further about what your experiencing as almost everyone of us here has prop issues! LoL

Pontoons are very difficult to prop correctly... Motor height is very curtial as is motor trim, as is load (passenger) distribution etc.

If your motor-pod has this V-Guard on it you might ask the dealer to confer with ST about removing it as it just hastens prop blow-out...

[HSS Heather]

Okay excellent. Thank you for confirming. I couldn't find anything on the web about the 60 ct and the 75 hp relationship.

As for the piece of metal on the bottom of the gas tank piece, I'm not sure, will have to investigate.

Currently the motor is as low as possible on the transom. If me and my wife are on the boat, there are no problems, but once there are 4 adults on board with two sitting forward, the motor starts having the gurgling noise and starts slipping on the water. Trim all the way down still doesn't help.

Pontoons are definitely a different beast!

[HSS Heather]

Also, I tried to trade up to a 90 hp but he wouldn't do it.

[teecro]

Also, I tried to trade up to a 90 hp but he wouldn't do it.

Well I would say find another dealer but your motor is now used and that's the only way he could resell it now as used... I traded my motor in at a Sun Tracker dealer (not a Bass Pro dealer) and he gladly gave me fair used price on my 1 year old motor in trade for a 75 which is max for my 18-ft...

Cut the thingy off the motor-pod, my motor would do the exact same BS even with 2 people on board if I didn't have a full tank of fuel... Now once cut off you might very well need to then raise one hole on the transom....

[HSS Heather]

Wow thats crazy that the little piece of metal made such a difference! I'll definitely cut it off, or have them cut it off.
Again thanks for your advise and experience sharing.

[HSS Heather]

I got the Big foot lower unit put on yesterday and tried it out on the lake. WOW. What a difference! All around performance is better, and the engine doesn't sound like a crotch rocket now. I was wowed by the large 4 blade prop.

[teecro]

I got the Big foot lower unit put on yesterday and tried it out on the lake. WOW. What a difference! All around performance is better, and the engine doesn't sound like a crotch rocket now. I was wowed by the large 4 blade prop.

That's good to hear! Did they use the 2.07 gearing from the 75 lower too? Sounds like they hooked up up with the 4-Blade Spitfire prop, yes it has massive looking "Dumbo" flukes...

[HSS Heather]

They said it was a "big foot" lower unit, although I was under the impression it was going to a 75 HP lower unit, so I'm not really sure which gear ratio it has. All I know is I'm in love.

[teecro]

They said it was a "big foot" lower unit, although I was under the impression it was going to a 75 HP lower unit, so I'm not really sure which gear ratio it has. All I know is I'm in love.

Yes that is indeed all that matters...

They only had two options here anyway
(A) Install a true "Command Thrust" lower unit intended for the likes of a 60CT which would have a 2.33:1 ratio
(B) Install the lower unit from a 75 or 90 which would have a 2.07:1 ratio