2016 Mercury 115CT

[Dan21XRS]

2016 Mercury 115CT 4 stroke
SN-2B224433

We're having a devil of a time proping a 2016 Sweetwater pontoon. Dealer has raised and lower the engine, switched prop a few times and are getting close, but we still experience prop blow out if we trim the engine while under power. Also, where they have it now if you trim the engine to trail it, the cowling will hit the back deck. Now they want to add a 5" extension so they can raise the engine back to it's original spot. Does anyone have any experience with this 5" extension??? Good, bad, ugly... Doesn't seem right, why would the manufacture put an engine on a boat and then spend extra $$$ when they should have just mounted the right engine in the first place??? Dan

[btsmbass]

All manufacturers transom pods are built a little differently. There is a black max xc special pontoon cup prop (part #: 48-78114CP1) made for that application. It is a 16"x13" prop that is recommended for that boat if it is a 20'-24' pontoon without lifting strakes.

Start at that prop, if that can't fix it, it is probably a geometry issue with the transom pod, any more work than switching props shows poor craftsmanship and you need a new transom pod that does not disturb the water to the prop. Also some pontoons without lifting strakes just aren't responsive to trim. It's a barge application, not a lifting one. Sometimes getting the trim past level is not an option.

[Dan21XRS]

Thanks for the response...

It's a 2286 Sweetwater, 22'3" with lifting strakes running the full distance of the pontoons.

Just makes me a little nervous adding additional length to the mid-section. More parts more potential problems is my way of thinking... Dan

[rickdb1]

Post a picture of the prop in relation to the bottom of the transom. That should tell alot of the story. I'm assuming you have a long shaft motor on there now (20")??

[Dan21XRS]

Yes the 20" version. Engine is/ was mounted in the third hole (1" off the transom) and was experiencing prop blowout at 4000 rpms with a 13.25x17 prop. Dealer played with it this week, lowered engine, and ran a 16x16 prop. Now he's saying that since he lower the engine the cowling now hits the back deck when trimmed for trailering and is still experiencing some prop blowout at WOT. So to fix that he wants to add the 5" mid-section extension so he can raise the motor back to the 3rd hole thus fixing the trim/ trailering problem and hopefully the prop blowout problem...


I guess my question is should I allow him to add the 5" extension to the mid-section??? Again, more parts more potential problems... Dan

[rickdb1]

I would leave the engine flat down on the transom and try a 13.75 X 15" Mercury aluminum prop and see how it does. My engine will also hit the sun deck when tilted all the way up. But I don't need to tilt it that far for trailering and I bet you don't either. Personally, I wouldn't put an extension on. It should not need it.

[EuropeanAM]

You can't spin a 17P prop on that engine, on that pontoon.

LOWERING the engine does not make it taller when trimmed- either someone got that mixed up, or you need to find someone far more knowledgeable in the "basics of setup" to assist you with this.

I'm estimating that you're at least 2 pitch points too high... possibly FOUR. Most commonly, that engine will perform well in the second hole (counting from the top), using Part# 48-78114CP1

[Dan21XRS]

Don,

Should I be concerned that they want to put a 5" extension kit on the engine? Right now they have a 16x16 stainless with the engine sitting on the transom. They're saying it runs well but there's too much engine in the water so they want to add the extension and then raise it back to the 3rd hole from the top... Dan

[EuropeanAM]

Yes, you should be VERY concerned.

If they are telling you the engine is too LOW... and they're adding a 5" extension kit, then raising the engine to the middle mounting hole: you will be approximately 3" lower than you are now!

Something here does not make even a touch of sense....

[FUZZYDP]

I have same engine on same size Lowe. Came with Blackmax 15 pitch. Got 29.3 mph @ 5400 rpm. No blow out unless you overtrim. In top hole. Going to vengeance 15.6X13. Your dealer is lost as a goose. Contact Sweetwater direct.