should i be getting more?

TinBoats.net

Help Support TinBoats.net:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

kyflshooter

Active member
Joined
Nov 16, 2011
Messages
35
Reaction score
0
16'sc gruman jon with 97 40 hp yam. only getting 25 hp out of it? shouldnt i be getting more? will post prop size when i get home. not sure on rpms no tach. but sounds good and jumps up quick. also recently rebuilt all decks in alum. and pulled all water logged foam from hull.
e690a55a-e76b-42bc-b46b-a0e8e17a1150.jpg
 
Ictalurus said:
Get a tach and first see what rpm range you are operating in.
Ictalurus is right. The stock prop that comes with your motor is sized to perform reasonably on any boat you put it on, but may not be the best for your hull. The last Yamaha that I had was a 90hp 2-stroke. It didn't have a rev limiter, that was the function of the prop. The marina tried a couple of different ones until we found one that gave a decent hole shot and would pull 5000 rpm at WOT.

I had a 16 foot Lowe deep vee that ran 31 mph with a 50hp 2-stroke Johnson, so I don't know if you are that far off.

Nice looking rig by the way.
 
Driftingrz said:
Im assuming he meant 25mph johny


That would surely make more sense but I try not to assume when it comes to boating questions anymore...... I have heard some real doozies over the years :-
 
One of those tiny tachs will help you out alot.
As fas as speed<I would think you should get in the low 30's.
I own a 1652 with a jet tunnel(running prop though);30hp,tiller and get 28+(gps).
Had a 40hp Suzuki a few years back and avg. run was 32mph.
Nice looing you boat.
 
Ok if we are talking MPH and not HP then that motor should easily push that boat over 30mph..... and very likely could hit 35-38mph if it were propped correctly and motor setup was dialed in. With a 2:1 gear ratio that motor can and should push that light boat over 35 without a problem.
 
yes that was typo, sorry fat fingers and working 3rd shift don't help, ok yes tach would help still figuring how to hook that up?, next that was taken on lake Cumberland at the state dock marina, 1st trip out ran ok considering been sitting for 2 years. Boat had alum. floor with spray foam under it that was completely water logged also 3/4 marine ply wood decks fiberglassed over so extra heavy there. after stripping all that and putting new 3/16 alum decks and and no water logged foam figured I shaved at least 200lbs or more out of it. so that is why I am disappointed in my mph turn out, ok now with the prop only markings I could find on prop is 4674 assuming those are yam. numbers for something. also boat has dumb roll on bed liner on bottom the black in the pic. also have most of it off but still need to paint I know that is creating drag but was figuring I could brake the 30 mark with out freash paint. motor idles rough and needs tune up but does good wot. I do have an exasut leak at the upper gasket not power head but next one down sorry for not knowing correct term. maybe paint ,exaust and prop will cure my blues
 
Ok that number is likely going to be useless that you gave off the prop. There should be a stamp on back of hub where your prop nut goes on or/and another stamp on the outside of the prop between propeller blades. Sometimes hard to see when painted over. Should read something like 11X15.

As for the exhaust leak you should have 3 gaskets pertaining to exhaust system. There is 2 behind exhaust cover housing #36-#37 in the pic and then the powerhead to exhaust gasket under the block. If you just have some exhaust leaking out of holes on back of the exhaust housing leg (exhaust ports) that is completely normal for a 2 stroke.
https://www.boats.net/parts/search/Yamaha/Outboard/1997/40ELRV/CYLINDER%20CRANKCASE/parts.html

One other question..... Does the boat get up to top speed and there is still throttle left? Meaning does the engine rev higher but boat does not go any faster.
 
ok its not ports in back, its coming up from under power head next gasket down upper case gasket i think checked power head gasket not it its just under it
 
would the leaky gasket hurt perfomance in my quest for speed and looked for numbers cand find on painted prop will pull prop off tom. and check hub
 
I'm running a 1998 tiller of the same motor you have, I am getting 35mph on a 1648 Sea Ark. My motor has a Mac's River Runner on the foot that probably cuts a couple mph off of it. I would check that exhaust leak first I think that would hurt alot of the performance.
 

Attachments

  • Hotmail (2).zip
    1.5 MB · Views: 18
kyflshooter said:
ok its not ports in back, its coming up from under power head next gasket down upper case gasket i think checked power head gasket not it its just under it

Not sure I am understanding you. Take a pic of the location of the leak and we can better help ya. As far as exhaust leak hurting performance....yes a little bit depending how bad. But 10mph seems to much for an exhaust leak. An exhaust leak usually depletes power from engine by contaminating the air under engine cover...less oxygen for ignition of fuel. Carbs suck in the low oxygenated air and combustion is weaker in the cylinder head, meaning less ponies. Take off your engine cover and run her wide open once...see if ya get a difference.

You shouldnt have to remove prop to see stamped marking on back of hub. Usually it is on the plastic ring that the nut and washer sit on top. Unless yamys are different? But you should be able to see it without removal typically.
 
https://s1.yzimg.com/000dcv0t8b2rmuao.640x480 on this motor you see the exhaust port and then you see where the cowling starts its leaking in between there.
when cowling is off and sitting in the water running you can look down around the power head and see no leaks but have exhaust leaking out from around that ring above the exhaust port in this pic. sorry for not knowing all the correct terms
 
Ok I'm picking up what your laying down now. I am not familiar with Yamy as well as I am OMC. And looking at your motor diagram it looks like there are 3 exhaust gaskets in there....eeek. And they all look like powerhead removal required. Actually I am not sure #10 in the diagram seals the exhaust, maybe just #24 and #20? Never had a Yamy apart......yet.

https://www.boats.net/parts/search/Yamaha/Outboard/1997/40ELRV/UPPER%20CASING/parts.html
 

Latest posts

Top