RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

[tystick]

I have exact same engine and 4800 is max. rpm
What size prop? It sounds like you may haveincorrect pitch and/or dia.
It should be at least 13 3/4 x 21 accordind to spec.
I do not think the nick on prop would reduce rpm.

 

[HuskerTx]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

I have exact same engine and 4800 is max. rpm
What size prop? It sounds like you may haveincorrect pitch and/or dia.
It should be at least 13 3/4 x 21 accordind to spec.
I do not think the nick on prop would reduce rpm.

I will check prop markings tonight to determine pitch and dia. Thanks

 

[QC]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

Make sure your tach is right. 3400 is really low and I believe she would really struggle to get on plane if the tach is correct. There is a switch on most of them in the back for 4, 6 or 8 cyl. I would check that first.

You should get a new prop and keep the messed up one as a spare. You need a spare!! If the steering wheel is not shaking as it is, then you might get away without repairing the spare one, although that would be the right way to do it . . .

 

[180shabah]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

A 4.3 at WOT should fall between 4400 and 4800. If you find you are propped correctly then more trroubleshooting will be required. ie when was the last tune up, what is the condition of the gas in the tank, etc????

 

[boathog]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

one nick can make a big diffrence , have it recond.

 

[HuskerTx]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

A 4.3 at WOT should fall between 4400 and 4800. If you find you are propped correctly then more trroubleshooting will be required.

I just pulled the prop and it has a Michigan 14.5X17 3 blade on it. Now that I look the prop is a bit beat up. However this seems like thr right dia and pitch I can't believe the dings will make a 1200 rpm difference. I am planning to try a new prop this weekend and see if that helps.

Thanks for all the GREAT feedback here. You guys make a new boater an easier job.

 

[180shabah]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

How's it going?????

 

[Huskersraider]

Re: RPM''s for Mercruiser 1990 Alpha One 4.3L 175HP

I have the same boat could you tell what size propeller is recomended. The one I have now is only 12"