2008 90TRL need more power!

[brodius]

I have a 90TRL on my 17ft seahunt. The boat can get up to plain ok but i can only get my RPMs to 3800 MAX. Good compression on all 3 cylinders. What can i do to get full power out of this motor? change propeller? Trim tabs?

 

[racerone]

Sounds like it is running on 2 of 3 cylinders.----Do a spark check next.----What pitch is the prop now?

 

[99yam40]

there is no such thing as a 90TRL.
is it a F90 TLR or maybe a 90TLR

did this motor ever push this boat at normal speeds and RPM?

 

[brodius]

My bad it is a 90TLR. I repowered this boat and have only taken it out for a few runs. It has never operated at full power. Attached is a pic of the prop

 

[99yam40]

I would look up some Performance bulletins for your hull with a 90TLR to see what prop was used and figure out what pitch that prop you have is

 

[racerone]

If that is a 23" pitch , you might try a 17" or 19" pitch.

 

[brodius]

I contacted the propeller manufacture to get some specs on my current prop. I also found this performance bulletin on seahunt 177. I have an older 172 but the boats are almost identical.

https://www.njoutboards.com/fckimages/performance23.pdf

 

[brodius]

So according to the prop manufacturer i am currently using a 13.5" diameter 18 pitch. That is the same as the performance bulletin that i posted. I will check spark and compression again but not sure if this is a prop issue

 

[99yam40]

High speed/main jets could be a problem if one is restricted.

 

[jimmbo]

I have a 90TRL on my 17ft seahunt. The boat can get up to plain ok but i can only get my RPMs to 3800 MAX. Good compression on all 3 cylinders. What can i do to get full power out of this motor? change propeller? Trim tabs?

You could check to see if the Throttle Linkage is advancing the Timing, and opening the Throttle Plates fully.

You also stated that it has never operated at full power. Is that you have never tried WOT or it just doesn't wind up? Also, is your Tachometer accurate?

 

[brodius]

I had my mechanic check the linkage. Not sure if it was done right tough. The tach is brand new yamaha digital tach. Brand new yamaha throttle also. I have tried running at WOT many times and only getting to 3800rpm. Any videos out there on checking linkage? How do i check that my new tach is correct?

 

[brodius]

spark and compression are good but compression numbers are a little low. 90s on all 3. Could that cause RPMs to fall that low?

 

[99yam40]

maybe the prop was repitched, so it is not what it was originally from the factory.
Low compression could be the gauge you used is not correct also

use a timing light to see if the timing is in spec and advancing as it should

only way I know of to see for sure if it is a motor problem is to find a shop that has the proper test prop for that motor and run it in a tank to see it hits the right RPM

 

[Kola16]

An 18 pitch prop would be about right for your boat and engine combo. Even if it was repitched, don't they only change it by up to 2" on stainless or so? I do not think the root of the issue is a prop problem. 16 to 20 pitch will be ballpark the correct pitch. 90 PSI, if your pressure gauge is accurate, is on the low end, but you should still be able to get to at least 4500 RPMs since they are all even. Closer to, or past 5000 RPMs with the correct prop.

1. Can you get the RPMs past 3800 at idle? See how high you can get the RPMs by using the idle accelerator lever on the remote. If you can redline the engine with the idle accelerator lever on the remote, then your linkage is probably good.

2. If it is still not redlining at idle with the idle accelerator lever on the remote, take the throttle cable off the accelerator lever on the engine (leave the engine in neutral). Move the accelerator lever all the way with the engine running. Does the engine redline now with you manually moving the accelerator lever? If it does redline, but did not for the first test, then your linkage needs adjusting.

If you answer those two questions, I can follow up with further advice from there.

 

[Scott Danforth]

spark and compression are good but compression numbers are a little low. 90s on all 3. Could that cause RPMs to fall that low?

Yes

 

[brodius]

New compression and readings are 115 on all 3. Good spark on all 3. The linkage is engaged all the way when throttle is WOT. Looks like I'm going to try some different props out on the water. I have a friend with different pitched props i can try out

 

[99yam40]

New compression and readings are 115 on all 3. Good spark on all 3. The linkage is engaged all the way when throttle is WOT. Looks like I'm going to try some different props out on the water. I have a friend with different pitched props i can try out

Are you sure the RPM and speed are low?
Make sure your tach is set up properly for your motor,
I would think you could tell if the motor was winding up to 5500 or not
can you get speed from a GPS?
Not sure if a smart phone app might do that

 

[brodius]

Reporting back. I tried 3 different props and finally found to correct prop that put me up to 5500 rpm. I had to drop down to a 13 pitch to get there. Thanks for help!

 

[99yam40]

Reporting back. I tried 3 different props and finally found to correct prop that put me up to 5500 rpm. I had to drop down to a 13 pitch to get there. Thanks for help!

very strange that you had to drop down to a 13 pitch if the performance bulletin showed an 18.
you need to find out if the motor has a problem or if boat does.

See if any of the shops around you have a test prop for that motor.
they should be able to test it in a tank to see if the motor will turn it at a set RPM without the boat being a load

 

[brodius]

I'm confused. The boat performed great with that prop all day.