changing from 2.07 to 2.38 gear ratio on a new motor

[2001SunTracker]

I am having problems finding a new Mercury 90 hp CT and have a dealer who is saying that he can put a gearbox from 115 CT on a regular 90 Hp. My question and worry is, does this void warranty, and does it put too much strain on a regular 90 hp motor, I'm thinking if they are interchangeable it shouldn't. Can someone help before I go and spend a lot of money only to find that I have made a huge mistake? Ps, my 21-foot sun tracker is only rated for a 90hp
Thanks

 

[ahicks]

A 90 4 stroke is a LOT of weight on the back of a 21'. Even the newest pontoons with the larger diameter pontoons. You may not care for how it squats the back of that boat. The fact it's rated for a 90 does NOT assure it's going to float level.

Why the change in gear ratios? What are you hoping to gain with this move? Is there anything wrong with the original?

 

[2001SunTracker]

Thanks for your reply, My old motor was only 50 bigfoot and I wasn't happy with the performance. I was told that I should be looking at the new Mercury command thrust engines that are meant for 18+ foot boats. As for floating level, it always seemed that the boat's front was riding low and had water come over the bow.

 

[2001SunTracker]

I am having problems finding a new Mercury 90 hp CT and have a dealer saying that he can put a gearbox from 115 CT on a regular 90 Hp. My question and worry is, does this void warranty, and does it put too much strain on a standard 90 hp motor? I think if they are interchangeable, it shouldn't. Can someone help before I go and spend a lot of money only to find that I have made a colossal mistake? Ps, my 21-foot sun tracker is only rated for a 90hp
Thanks

 

[jimmbo]

Both the CT90 and the CT115 have the 2.38 gearcase. The 90/90CT and 115/115CT all share the same Displacement, and both engines of each design have the Weight. The CT models utilize the Larger V6 Props, and will handle heavy loads better, and have greater Thrust for easier maneuvering. There will be a slight loss of top speed due to the extra drag.
Being that it is being done by a Dealer and with OEM parts, shouldn't affect the warranty, as there is 90CT model in production, but discuss the warrantee concerns with the Dealer,

https://embed.widencdn.net/pdf/plus/mercurymarine/oceb4dh8gm/propulsion_brochure.pdf?u=orhjei

 

[2001SunTracker]

Thank you for replying and I also decided to call Mercury corp. they are telling me unless the dealer has certain arrangements with Mercury in writing, I should be careful. They are saying any medications to a new engine very well void warranty. For the cost of a new motor that is the last thing I want to happen. It very well be the dealer I’m working with might warranty it, but what happens if I need to go elsewhere. Thanks again.

 

[JimS123]

Make your dealer sign and notarize a written statement that he will honor the warranty after he makes the change.

If it were me, I'd simply use the standard gearcase. There are props that will do the job as long as you get the needed data.

Regardless, I would not trust anyone to change the lower unit. Too much to go wrong. (I have limited respect for customer service and mechanics abilities in todays world.....but thats just me).

 

[2001SunTracker]

I agree 100% Thanks for your honest opinion

 

[Chris1956]

Gee, a trained monkey can change a gearcase. He does need to be trained, though.

 

[QBhoy]

A 90 4 stroke is a LOT of weight on the back of a 21'. Even the newest pontoons with the larger diameter pontoons. You may not care for how it squats the back of that boat. The fact it's rated for a 90 does NOT assure it's going to float level.

Why the change in gear ratios? What are you hoping to gain with this move? Is there anything wrong with the original?

They are very light to be fair. I’ve the same engine but the 115. They only weigh 160 kgs. As light or lighter than most 2 strokes of 115hp at least. I’ve got mine on a 19ft.

 

[ahicks]

They are very light to be fair. I’ve the same engine but the 115. They only weigh 160 kgs. As light or lighter than most 2 strokes of 115hp at least. I’ve got mine on a 19ft.

We'll need to agree to disagree regarding "very light".

160kg = 353lbs. Does that number include the power trim?

An 85 Johnson is a hundred lbs lighter, and much more likely the weight the folks doing the 90 hp rating had in mind

50-60 hp 4 strokes are about 250 with t&t. My experience would have a motor this size, from a weight standpoint, all you would want on an older 21' pontoon.

Do as you like!

 

[QBhoy]

All you’d need to do is get a suitable prop. Great news is that the CT uses a huge range of props

We'll need to agree to disagree regarding "very light".

160kg = 353lbs. Does that number include the power trim?

An 85 Johnson is a hundred lbs lighter, and much more likely the weight the folks doing the 90 hp rating had in mind

50-60 hp 4 strokes are about 250 with t&t. My experience would have a motor this size, from a weight standpoint, all you would want on an older 21' pontoon.

Do as you like!

being fair…I suppose I was meaning more for the 115 badged version I have (which is the same engine…75-115 are the same 2.1l) and I know nothing about pontoon boats either.
But there is no doubting it’s a record breaking engine and the lightest of that power on the market currently.

 

[ahicks]

QBhoy, we're talking a 21' pontoon boat here. The "right prop" is not going to have ANY effect on the ride height of the back of the pontoon boat which is weighted down with way too heavy a motor....

Same story with the gear ratio. EITHER ratio won't change a thing.

NOT TALKING RUNABOUT HERE!

 

[QBhoy]

QBhoy, we're talking a 21' pontoon boat here. The "right prop" is not going to have ANY effect on the ride height of the back of the pontoon boat which is weighted down with way too heavy a motor....

Same story with the gear ratio. EITHER ratio won't change a thing.

NOT TALKING RUNABOUT HERE!

Like I say. I bowed out earlier, knowing nothing about pontoon boats.
Amazing that a 21ft pontoon thing can’t take a 90hp though.
Just a quick look at the first one that comes up on google…a sun tracker 21 or 22…comes fitted with the 115 merc (Exaxt same engine discussed above) command thrust. The 22 xp (or something) comes with a 150 merc. Just about every boat like that I see online, is spec’d with a command thrust merc.
But like I say. Not something I’m familiar with. Just pulled the first one that came up.

 

[ahicks]

Like I say. I bowed out earlier, knowing nothing about pontoon boats.
Amazing that a 21ft pontoon thing can’t take a 90hp though.
Just a quick look at the first one that comes up on google…a sun tracker 21 or 22…comes fitted with the 115 merc (Exaxt same engine discussed above) command thrust. The 22 xp (or something) comes with a 150 merc. Just about every boat like that I see online, is spec’d with a command thrust merc.
But like I say. Not something I’m familiar with. Just pulled the first one that came up.

The latest generation of pontoons have larger pontoon diameters able to carry more weight, and the "cabin" area moved forward slightly to help offset the bigger motors being used lately.

Point being you have a legitimate point - when talking 'toons built within, say, the last 5 years or so.

 

[QBhoy]

The latest generation of pontoons have larger pontoon diameters able to carry more weight, and the "cabin" area moved forward slightly to help offset the bigger motors being used lately.

Point being you have a legitimate point - when talking 'toons built within, say, the last 5 years or so.

No probs. No doubt, you’ll know more than I about it.