2000 90hp carb on 16 alum boat around 1300pounds

[200090tlry]

What speed/rpm should I be getting at 5700 altitude. Prop is 17 yammy. Just ran boat for first time at lake. Most rpms I could get around 4000. With my math that does not seem right. Speedo wasnt hooked up bummer but fishfinder paddle wheel said 38mph and change seemed slower. Motor was quiet compared to Mercury 115hp boat I sold that thing ripped sounded like alchol dragster loud and powerful. Also I played around with motor over winter, there was a red switch thingy near carbs under plastic air baffle. What is right setting for this thing and what does it do.

[99yam40]

Check out this site and see what a setup like yours did, but I have no idea if something different needs to be done to a motor for that high of altitude. Maybe different jets, because of less O2 available in the air.

Performance Bulletin Home

http://www.yamaha-motor.com/assets/p...x165-90tlr.pdf

I believe that red lever is the emergency switch, should be in the normal position unless you have a problem with plugged passages in carbs/prime start system, then turn to open to get motor started and then switch to off to run back to port and have motor fixed

[throrope]

Speed sounds in the range, but the rpm's are off. We run that outboard on a 21 ft skiff with T-top that weighs in around 2000# fully loaded and run 35 mph at 5500 rpm with 15 inch pitch. Before the top we ran 40 mph.

Like 99yam40 sez, the red switch thingy is an emergency valve that dumps fuel in the event you have issues. The correct operation can be found in the owner's manual available free from Yamaha's site. Outboard Owners Manuals I suggest getting the service manual that is also available for purchase.

If it doesn't run right in the normal position, you may have a problem with the fuel enrichment device (fancy choke) or your carbs may be clogged. Not only did we have both, but an orangutan at the prior owner's marina miss assembled them and left a load of crap behind.

Given the age, you may have collected crap in the carbs due to ethanol in fuel. Older fuel hose etc. were not formulated to withstand the alcohol. You should find brass drains on the bottom cover or bowl of each carb. CAREFULLY opening them with a wrench is a quick way to see if they have crap in the bowl which means throughout. Don't loose the O-ring.

Since your rpms are low, you may also want to try different pitch props.

These outboards are tried and true work horses with an awesome power to weight ratio and need only simple hand tools for service. The more I learn, the more I like ours. This is an awesome site for replacement parts and I haven't found another that discounts MSRP and delivers to your doorstep.

Hope this helps, good luck and keep us posted.

[200090tlry]

Yes motor did not seem to have the mean kitty growl

All 2strokes ive owned in past mecury's were little mean. While flooring it it's strange only to get 4000rpm. Maybe there is fuel restriction somewhere in motor. I think everything is working fine? The pilot screw does this just adjust low speed idle. Im pretty sure with this one a prop will make no difference. So the red switch is fuel cutoff? Do these motors electronic go in some mode 4000rpm max. Boat comparison is very close mines little more beefy crestliner superhawk. It's fast hull though, for sure something is not set right on my rig. I had 17 fiberglass with mercury 80hp and it would kick it up notch vrrrroomm. Yamaha should have little more zip.

[99yam40]

I would recommend taking it to a good Yamaha shop and have it checked out by a trained Yamaha tech to make sure it is not a motor or set up problem

A motor trying to turn too big of a prop will not get to the proper WOT RPM.
A motor not hitting on all cylinders will not hit proper WOT RPM
If the motor is not getting enough fuel to create the HP needed or the air is too thin to burn all the fuel properly to get the HP it does make a difference to go to smaller prop.
But you need to make sure the carbs are not the problem, because if it is running lean it will get a piston.

No there is no RPM reduction to 4K only 2K from overheat and low oil.
Pilot screws adjust the amount of idle fuel/air mix not RPM.
Red lever has 3 positions normal, open,& closed

[throrope]

While flooring it it's strange only to get 4000rpm.

If you can't get mfgr's max rpm at WOT on plane, something's not right. IMHO, 6,000 ft elevation shouldn't be causing that grief.

The pilot screw is on the air side for idle. I saw in posts here should be around 1-1/4 turns out. I found much more help through searches. Bad idle and adjustments out of norm are often tattle tales of difficulties.

As far as the red thingy, again, please look at the owner's manual. I think you will also find basic troubleshoot info, bypasses and RPM limits when the outboard sensors detect trouble like low oil, high temp, etc.

The SERVICE manual is cheaper than a trip to the dealer and includes all diagnostics, linkage adjustments, detailed diagrams and repair procedures. Even if you don't want to mess with it, you will know what the shop is talking about.

The guys at PowerTech Propellers ptprop.com can run your rig on their computer program and give you a sanity check on prop size & pitch.

These outboards are awesome, boats are too expensive and your time is too valuable to let incidentals tarnish your fun.

[rodbolt17]

6000 ft high makes a HUGE difference if your engine is jetted,geared and propped for se*****l.
we can debate,yak,BS and shoot de sheet all day.
however a quick trip with Yamaha test wheel YB1620 will tell the story.
in 15 minutes you can tell if the engine output is correct and if you have rigging/hull issues.
any competent Yamaha dealer can run this test.
if the engine can spin YB1620 at 5100-5300 RPM your engine output is as specified.
if not there is an engine issue.
but be aware that altitude makes a big difference in an articulated rod normally aspirated internal combustion engine.
its basically an air pump.
the thinner the air the less power avalible.
there ae several charts that deal with the percent of loss for each 1000 ft of altitude.
its also why old aircraft engines were supercharged.

[200090tlry]

Ok just cleaned out carbs

They were in pretty nice shape like previous owner had them cleaned not long ago. Do have a question on needle, the spring looks little bent maybe my towel grabed it. I put it back in seems to work but wonder how sensitive these are. How do I adjust screw setting for floats 2000 90 hp tlry carby. While doing more investigating put the throttle forward all way seems timing stops 1/2 to 3/4 hits stopper, butter fly's are not open all way still. Should butterflys be almost all way open at full throttle? I can do seperate post for this once I figure floats and reinstall everything. I know there is link and syn procedure hopfully I can get some help. This would explain no kitty growl and 4000 rpms.

[99yam40]

If these floats are anywhere close to my 40 they do not have a screw setting for the float setting

Sounds like you do not have a Yamaha or any other service manual for this motor, get one and read up. It is full of information that you need now and later.

How long has this motor been rigged on this boat?

Has this set up ever run properly?

What HP is this boat rated for?

If the throttle is not set up properly, which that is what it sounds like, then another question would be is the motor even mounted properly on the boat?

[200090tlry]

Ok played around some more with outboard

I looked at links and stuff considered moderate to easy to do adjustments. Maybe im nervous about playing around with rods and stuff. The square black box with I think timing hash marks line up like they should both at idle and WOT. I checked the butterfly's again and I guess they did open up fine once everything was installed back together. Im going to try comp test but have a feeling it's solid. If this motor was from Florida and I wanted to use at 5700 altitude would I really see that much difference leaning out fuel with new jets? Right now 4000 rpm would I pickup 1100 rpm? Boat is Crestliner Superhawk 1600 max hull rating 90hp. It's solid 1000 pound boat without all adds batteries,seats,motors crap. Also is pretty fast hull for deep v all welded. Just guessing I should be around 40mph. The 17 pitch prop is new yamaha. I ran 115hp mercury 2+2 on 17ft same boat slighty heaver 300 pounds, top speed 46 with 19 pitch mercury performance dropped alot when I purchased 17pitch Solas and got vibs actual rpm picked up but lost speed like 40mph. So If I do switch props from 17 on this boat will I get 400 rpm for every 2 pitch drop. 13 pitch would be crazy for 90hp I think, maybe the rejetting is way to go. I also just looked at speedo put my pump on end and got it to work maybe it was rusty from sitting few years. Will lake test again, the red enricher valve has normal,open,closed. Should I try running with it closed.

[99yam40]

take Rodbolts advice , he is a Yamaha master tech.
I have no idea if you can or should re-jet a motor for different altitude.

6000 ft high makes a HUGE difference if your engine is jetted,geared and propped for se*****l.
we can debate,yak,BS and shoot de sheet all day.
however a quick trip with Yamaha test wheel YB1620 will tell the story.
in 15 minutes you can tell if the engine output is correct and if you have rigging/hull issues.
any competent Yamaha dealer can run this test.
if the engine can spin YB1620 at 5100-5300 RPM your engine output is as specified.
if not there is an engine issue.
but be aware that altitude makes a big difference in an articulated rod normally aspirated internal combustion engine.
its basically an air pump.
the thinner the air the less power avalible.
there ae several charts that deal with the percent of loss for each 1000 ft of altitude.
its also why old aircraft engines were supercharged.

If the prime start system is functioning properly, it does not enrich after motor warms up in normal

[Michael j]

Did you check to make sure the tack is rIght ?

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[200090tlry]

Not sure if tach is correct

But I just hooked it up and put on number 6 omc faria tach with system check, you double x 2 to get 12poles I think. There's only 5 and 6, think it's working properly. Maybe this longshaft yammi lower unit is different year like late 90's and steep gearing? Would not be suprised if lower and upper are mixed and matched years. Would be fun if Rodbolt was in my area I would hire him and play around with it.

[99yam40]

Sounds like you do not have a Yamaha or any other service manual for this motor, get one and read up. It is full of information that you need now and later.

How long has this motor been rigged on this boat?

Has this set up ever run properly?

is the motor even mounted properly on the boat?

Pick up a manual read up
like Rodbolt said take to a Yamaha shop that can run it with the test prop and see if there is a motor problem.

You never answered the questions on mounting of this motor and did it ever run properly