high rpm, little speed mariner 150

BarflyRIB · 07 March 2010, 18:01

today we had a big trip planned, unfortunately I was just away and the engine did very weird - it's a mariner 150 '96 - when I throttle up, the rpms get up but no speed similar to this rpms, when I throttle back very slow the rpms goes down and suddenly the engine gets in gear and boosts up... it's like the propellor slips... when I did WOT, I was making speed but not the "G force" feeling you know... very very slow to higher speed...
I recently changed the spark plugs and it's another type than before...
anyone had the same problem? what could it be?

EDIT: getting it in back gear was also a problem...

Downhilldai · 07 March 2010, 18:49

Sounds like you're spinning the prop bush

BarflyRIB · 08 March 2010, 10:10

Quote:

Originally Posted by Downhilldai

Sounds like you're spinning the prop bush

ok thanks, I will check the prop bushing - I remember it was like at a certain RPM level the prop gets his full grip and you could feel it (the boost :-) )

jambo · 08 March 2010, 10:23

As you can see I have the same engine and had problems last year!! Have you checked your fuel system right through/ Eventually got my problem as a dodgy diaphragm!!
Hope this helps you get back on the water.

J

9D280 · 08 March 2010, 12:45

I had a similar thing on an old Johnson 25. Check round the hub of the prop - if you see a ring of "extruded" rubber (paint in that area wil lbe flaked off as well) , you're looking at a new prop. Basically if it's hit something, the bits of the rubber moulding (injected into place when the prop was made) break form their holes, and then you're just relying on the friction, which isn't enough, and so the hub starts to spin relative to the body, then of course the rubber starts to melt & it gets worse.......

wavelength · 08 March 2010, 13:45

used to be a regular problem in the early days of thru prop exhausts even with relatively low hp models on the local fishing boats, but not seen much trouble with this for a long while-perhaps I've just been lucky eh. Trouble is you cant really feel any difference with the prop on the bench, just shows up in the way you say-the bush just lets go at certain loads. New prop methinks.

Poly · 08 March 2010, 14:05

Quote:

Originally Posted by wavelength

New prop methinks.

can steel developments and the like no replace the bush?

biffer · 08 March 2010, 14:11

Quote:

Originally Posted by Polwart

can steel developments and the like no replace the bush?

yes

chewy · 08 March 2010, 14:43

Quote:

Originally Posted by Polwart

can steel developments and the like no replace the bush?

Thats if you can get a sensible answer from the lass on reception first.

9D280 · 08 March 2010, 16:24

Quote:

Originally Posted by biffer

yes

Bearing in mind what they would have to do (clean out old bushing, line it all up, re- inject new rubber, then balance it all up again) I have to ask, assuming it's a standard off the shelf ally prop, would a replacement not be cheaper?

A nice stainless tuned to the rig one fair call to re- bush.

biffer · 08 March 2010, 18:09

any prop place should be able to bush it, streamline props, poole propellers (i think) do a search for prop repair

ashbypower · 08 March 2010, 18:42

Hang on do mercury not use a seperate Torque ? drive bush on their larger motors? our Opti certainly is so equipped !!

Bigmuz7 · 08 March 2010, 18:50

Quote:

Originally Posted by ashbypower

Hang on do mercury not use a seperate Torque ? drive bush on their larger motors? our Opti certainly is so equipped !!

Yes I think they do .. you can knock it out IIRC

ashbypower · 08 March 2010, 18:54

Quote:

Originally Posted by Bigmuz7

Yes I think they do .. you can knock it out IIRC

Yup sure can

BarflyRIB · 08 March 2010, 20:03

this evening I took the prop off, see the pictures

wavelength · 08 March 2010, 21:06

Quote:

can steel developments and the like no replace the bush?

probably but I'm a fully paid up member of the throwaway society and couldnt be ***** with mucking about, posting it, being promised turn around times that don't materialise etc etc.

Bigmuz7 · 08 March 2010, 22:01

Cant remember which way it comes out .. in either pic 2 or 3, but there should be a rubber collar inside , which could be the bit thats got minced up, check that first

BarflyRIB · 09 March 2010, 07:03

i have here another laser 2 prop with flo torque (comes from optimax 200) - I suppose this prop will fit also the mariner?
I will test this first next weekend, to check if it's the hub or not

BarflyRIB · 13 March 2010, 16:49

today tested another prop but the problem still occurs.. should a bad carb setting could be a cause?

wavelength · 13 March 2010, 17:06

if you are actually getting the revs as you say but not the usual speed asociated with those revs on your boat then sommat after the crankshaft is slipping surely. Either the spline connection to the drive shaft, the prop hub or perhaps the boat is heavy for some reason such as waterlogged foam under the deck and the prop cannot push it so it is losing grip with the water and slipping more than usual there.