4.3L TKS Jetting and Props

[hyperlite33]

I am thinking about taking my 185 to Lake of the Ozarks and was wondering if I should be looking into getting it jetted or different props.

Right now I have the 4.3l TKS with 1.81 gear ratio and the 19p High Five prop.
I also have the stock aluminum 3 blade 19p prop as backup.

Will I be be okay with the current jetting at 5500' asl going to 600' asl? Would either prop be okay or should I start looking for a 21p?

Thanks!

 

[Dave 205]

I've seen some documentation that calls your 1.81 ratio a "high altitude" option. Mine is 1.62. Not much you can do there. No idea if your carb also would have a high altitude option - your dealer should know, and tell you if it will give you much trouble with the big drop you'll have. I suppose it is possible props are adjusted to various ratios, but one would think power delivery under the water isn't going to have any impact due to altitude, probably not an issue unless you want to experiment with props for other reasons.

The 4.3 should generally make your boat hustle, and the low altitude might make it even more fun then you've known. I've been to the Ozarks, its a lot of fun, but know that it is a big lake that can have a lot of big boat traffic at peak times that can make boats like yours and mine a bit tedious in the chop.

You may be coming out of the mountains, so this may not be an issue for you. But, the hill country around the lake can be a lot of work if your tow vehicle is marginal in relationship to your boat.

 

[blaster]

The standard ratio on the 4.3 carb is the 1.81 the 4.3 mpi has the 1.62 ratio. You shouldn't need to jet the carb, if anything you may need to adjust the fuel air mix. My friend with a similarly powered 185 ran at sea level with a 21" stainless prop and did well. I think some even run a aluminum 23". You can run the 19" just be careful not to over speed. If you are used to 5500' then low altitude will open up a new level of performance for you. Even with heat and humidity the performance improvement should be very noticeable.

 

[hyperlite33]

your dealer should know, and tell you if it will give you much trouble with the big drop you'll have.

I wish I could, but 2 months after I bought my boat, the dealer closed its doors. I really don't have a boat dealer anywhere close to me, let alone a Sea Ray dealer.

The standard ratio on the 4.3 carb is the 1.81 the 4.3 mpi has the 1.62 ratio. You shouldn't need to jet the carb, if anything you may need to adjust the fuel air mix. My friend with a similarly powered 185 ran at sea level with a 21" stainless prop and did well. I think some even run a aluminum 23". You can run the 19" just be careful not to over speed. If you are used to 5500' then low altitude will open up a new level of performance for you. Even with heat and humidity the performance improvement should be very noticeable.

That's good to know I shouldn't need to rejet. If I need to mess with the a/f screw, will I know by the engine not starting or running rough?
I may also keep my eyes open for a 21p as backup, and leave the five blade at home.

 

[blaster]

That's good to know I shouldn't need to rejet. If I need to mess with the a/f screw, will I know by the engine not starting or running rough?

If it were me I would see how it runs first. If you do need to adjust the mix start by turning the screw all the way in and count the revolutions. That way you know where it was set to start with. Then back the screw out to where it was, start the engine and adjust the mix to achieve the desired result. Coming from altitude you may need to back the screw out a little to run more rich. Most carbs are factory set for sea level. If it was jetted for high altitude and you are moving the boat to sea level permanently then a re jet may be warranted. For short term use though there should be plenty of room to adjust the mix and tune in for good performance. I would run it a bit to warm up and measure performance then let it cool a bit and pull a spark plug. Brown color good white lean and black and wet rich. As far as dealers go, any Mercury dealer can help you, not just Sea Ray dealers. I'm no mechanic but that's what I did when I went to a hi altitude lake. I dropped 2" in pitch and adjusted the mix and it worked great for my old boat. My electronically controlled engine in my new boat eliminated having to make any adjustments to the motor. I still use a lower pitch prop above 3000'.

 

[Dave 205]

I dropped 2" in pitch and adjusted the mix and it worked great for my old boat. My electronically controlled engine in my new boat eliminated having to make any adjustments to the motor. I still use a lower pitch prop above 3000'.

How does that work with the pitch of the prop by altitude? I'm assuming this is just trying to adjust to a drop in engine performance? Or is there more to it?

 

[blaster]

Altitude kills HP so when your at a high altitude you loose RPM'S. dropping pitch compensates for the RPM loss. For the OP It's the opposite. There is thinner air at higher altitude so you need the engine to run more lean than you would in the dense air at sea level.

It's nice to hear from you Dave, have a happy Easter.

Luke

 

[minty fresh]

I would try it out, but if it's been leaned out for high altitude it may surge down around sea level. Pay attention to how it runs at cruise. If it surges or runs hot, you may need to jet it up a bit. Your mixture screw will only make it run better at idle, which you will probably want to mess with since there is a lot of idle time around the dock and during water sport.
Travis..

 

[hyperlite33]

I would try it out, but if it's been leaned out for high altitude it may surge down around sea level. Pay attention to how it runs at cruise. If it surges or runs hot, you may need to jet it up a bit. Your mixture screw will only make it run better at idle, which you will probably want to mess with since there is a lot of idle time around the dock and during water sport.
Travis..

Not really sure if it is leaned out for altitude, only thing I found out is that it came from the salt lake dealer to the Denver dealer. Since the Denver marine max didn't even set the trim tabs from factory (another issue I had), I doubt they changed them.
Its been awhile since I messed with jets (Yamaha banshee quad) so I will test it when I get there and hopefully be able to adjust rather than re-jet.
Anybody going to lake of the Ozarks the end of June?

 

[all about fun]

Not really sure if it is leaned out for altitude, only thing I found out is that it came from the salt lake dealer to the Denver dealer. Since the Denver marine max didn't even set the trim tabs from factory (another issue I had), I doubt they changed them.
Its been awhile since I messed with jets (Yamaha banshee quad) so I will test it when I get there and hopefully be able to adjust rather than re-jet.
Anybody going to lake of the Ozarks the end of June?

I was down there last July. My sister and brother in law keep a 30' fly bridge at Silver Sands Resort mm 38.5. They have cabins for rent also - cleaner than a hospital and nice people. A couple things about the Ozarks...warm water and Captain Ron's (gotta go). Find a cove on the weekend and hang out or you'll get knocked around.
Go Broncos!

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