Just bought a new motor for my RIB but didn't realize it was a high thrust

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
So as the title states, I bought a new(used) Yamaha 8hp 4 stroke for my RIB and didn't notice until I got home that it says high thrust on the cowl.. Can't get the exact model number since the sticker is worn away, but the motor looks new. I got a number off the emissions label but that didn't produce anything from google. So what exactly does high thrust mean on a 8hp yamaha(T8 I think)? Is it just a different prop or did yamaha put lower gears in the T8's? What can I do to make this motor work well with my 10' hard bottom Walker Bay RIB? I know it will work fine as it but I don't need all that power down low... I'm not a tow boat lol. I like to use my dingy for sightseeing a lot.
 

ronaldj

Senior Chief Petty Officer
Joined
Apr 1, 2013
Messages
655
So as the title states, I bought a new(used) Yamaha 8hp 4 stroke for my RIB and didn't notice until I got home that it says high thrust on the cowl.. Can't get the exact model number since the sticker is worn away, but the motor looks new. I got a number off the emissions label but that didn't produce anything from google. So what exactly does high thrust mean on a 8hp yamaha(T8 I think)? Is it just a different prop or did yamaha put lower gears in the T8's? What can I do to make this motor work well with my 10' hard bottom Walker Bay RIB? I know it will work fine as it but I don't need all that power down low... I'm not a tow boat lol. I like to use my dingy for sightseeing a lot.


You might want to check that
The 8 hp tend to be short shafts
The High Thrust tend to be lLong Shaft an 9.9 hp

Dosent your Walker Bay need a short shaft
 

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
Yes I need a shortshaft, and the one I got is short. Let me go measure it to make sure, it looks short anyway. Maybe it's a SS with a T8 cowl? Really wish I could get the model number off the tag, I'll look for a serial number. Maybe it's stopped raining enough for me to go look
 

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
You know what..... I think he(guy I got it from) painted this cowling and put new stickers on it and maybe put a highthrust "8" sticker on there instead of the regular 8. He told me he'll paint cowlings if need be and put new stickers on them, buys/sells/trades kickers as a hobby. One of the stickers looks like it still has the clear plastic outer film/cover on it. He kept going on and on about how new the motor looks, which it does, but a newly painted hood might explain his high opinion about it.

Found a S/N sticker on the block 1014604

Hard to measure length with it laying in the back of my truck but got something roughly around 18"
 

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
Seems like I might be answering some of my own questions lol.. The F8 comes 2 models:
F8MSHC ? manual trim with manual start 15″ shaft and tiller handle
F8MLHC ? manual trim with manual start 20″ shaft and tiller handle
The T8 comes in 6 different models:
T8ELHC ? manual tilt w/ elec. start 20″ shaft & tiller handle
T8PLHC ? Power tilt w/ elec. start 20″ shaft & tiller handle
T8PLRC ? Power tilt w/ elec. start 20″ shaft & Remote control
T8EXHC ? manual tilt w/ elec. start 25″ shaft & tiller handle
T8PXHC ? Power tilt w/ elec. start 25″ shaft & tiller handle
T8PXRC ? Power tilt w/ elec. start 25″ shaft & remote controls

Mine is a tiller pull start manual trim, and likely short. So it may be an F8 after all. Will have to call Yamaha with the s/n to know for sure I guess
 

alanfox55

Chief Petty Officer
Joined
Nov 17, 2011
Messages
476
Try going to the Yamaha section of this forum and ask your question.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Both being portable OB's, the standard model and the kicker surely have same gear case ratio, the difference is the prop. Does OB have a 3 or 4 blade prop ? Anyway to check if prop is top for your boating needs, need to install an induction tach, go for a wot spin as usually loaded to check max wot rpm, will know if inside min-max wot rpm factory range for that 8.

If having a 4 blade prop check which pitch coms factory delivered with the standard 3 blade prop for the 8 model, that should be your starter prop for your application.

Happy Boating
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
The two models are very different, different gearcase with different ratio. Some times you can use the T8 for the same application as the F8, but the problem is finding a prop with the correct pitch, the T8 isn't designed to plane a boat, and the prop selection is limited.
 

ronaldj

Senior Chief Petty Officer
Joined
Apr 1, 2013
Messages
655
As long as it is a short shaft then half the battle is won.
There is nothing worse than trying to use a long shaft outboard on a short shaft boat
 

silverplate

Recruit
Joined
Jul 24, 2016
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[h=1]http://www.polymarine.com/advice/zodiac-dinghy-transom-repair/[/h] try this for repair info
 
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