Yamaha F100D Not Getting Revs

[hydropassion]

Hi All,

I'm a little stumped. Transplanted Yamaha F100D onto Reef Ranger bought recently. All set up properly as far as I can tell. Dropped into water and can only get 3200 rpm out of motor. The boat came with 160 liter tank. I filled tank with 100 litres thinking that any problems with fuel would be diluted. Filters all look clean. Tank breather also looks fine - has canister fuel/air separator on it. The Cav plate on the motor sits at level with bottom of pod although that is 50mm higher than bottom of keel. Thinking about hooking up small fuel tank with fresh petrol to see what happens. If anyone has suggestions they would be very much appreciated. One person suggested it was a prop issue but I find it unlikely that a prop issue (has 13.25 by 19 standard Yamaha on it) could cause this much problem. Over to you....

[antonywardle]

Can you rev higher from the cables in the engine ?

Maybe they aren't pulling the throttle as far now

[DrownNprawns]

does it rev higher when not in gear then may be prop. if not then it will be fuel or spark

Hope this helps

[jeffb5.8]

Like anthonywardle said, with the motor off in gear and throttle arm at full throttle, is it at full throttle at the engine or is there more movement.

I only have experience with small outboards but hoping the 100hp is similar

Edited April 1, 2016 by jeffb5.8

[tackleberry]

faulty temp or oil pressure sender ?

[bessell1955]

Blockage in the fuel delivery system?

[Spinner 2]

If it idles o.k,... I'd say you either have a fuel line blockage or "Gummed up" fuel delivery system. I have had this problem and I gave the fuel tank a heavy dose of a product called Fuelmaster. if you have 100 Ltrs of fuel in the tank give it 200mls of this product, then run the engine for a few minutes, then let it "soak in " overnight. then start the engine the next day and the Fuelmaster should have dispersed all the "gum or varnish"

[Geoff]

If it rev's out to 5000 - 6000rpm in netural then it is the prop.

If not then check the linkages to see if throttle connection in the motor are opening 100%

If it's fuel , the motor will tend to surge rather go to 3200 then go no further

I dought it is electrical as it will start missing when the load gets to 3200

[antonywardle]

any update?

[BWV]

If it rev's out to 5000 - 6000rpm in netural then it is the prop.

not correct, the prop size sounds about right, give or take.

it could be numerous things but start simple and connect it is another fuel source. Check linkages. Check filters and fuel line, it maybe starved of fuel under load. Electrical problems usually happens at all revs but not always.

[hydropassion]

Hi All,

Thanks for all of the replies. I replaced the fuel filter and all fuel lines out of main tank. Took it out and pulled 5400 rpm at about 32 knots. Changed prop back to 17 and pulled 5800 and roughly same top end. Cruising speed at 4500 is 21-23 knots. Very happy with this. Not sure how it will go on the fuel but will find out in due course. Thanks again. I did not think I'd get anything like the top end I've got. Also putting some trim tabs on so will see if that are differences out of the hole.

[SquidMarks]

Even though you are getting the same top end out of higher revs with the reduced pitch, you should be getting better holeshot and on the plane faster!