What too look for when purchasing a new prop ?

[alan ber]

I have a 1984 Mercruiser
Model is 488 R
3 liter engine
alpha 1
powers a 21 ft boat

no trim tabs
have been told under powered for a 21 footer but the 488 is a work horse good engine & burns little fuel

Getting on plane is slow process , stern digs in, cant get out of its own way but eventually gets up there.

Mfg calls for a 13 3/4
21 " pitch
3 blade

Considering changing prop
What should I look for?
I baby engine as everything is original and I seldom open it up as I generally fish in no wake areas of intra coastal here in sunny warm Florida,

When I pulled props section on I Boats it gave me a variety of props from 12 " pitch up too 21 " pitch all for my model ??
I understand having no trim tabs slows up a bit , but I want is boat too be more responsive, get up on plane faster.
Larger Prop does what ?
Smaller prop does what ?
Larger pitch ?
less pitch? ?

aluminum verses stainless
3 blade verses 4 blade and double stackable with 6 or 8 blades ??


Cant purchase 12 blades too see what works best for my boat

thanks

 

[Bondo]

Re: What too look for when purchasing a new prop ?

I have a 1984 Mercruiser
Model is 488 R
3 liter engine
alpha 1
powers a 21 ft boat

no trim tabs
have been told under powered for a 21 footer but the 488 is a work horse good engine & burns little fuel

Getting on plane is slow process , stern digs in, cant get out of its own way but eventually gets up there.

Mfg calls for a 13 3/4
21 " pitch
3 blade

Considering changing prop
What should I look for?
I baby engine as everything is original and I seldom open it up as I generally fish in no wake areas of intra coastal here in sunny warm Florida,

When I pulled props section on I Boats it gave me a variety of props from 12 " pitch up too 21 " pitch all for my model ??
I understand having no trim tabs slows up a bit , but I want is boat too be more responsive, get up on plane faster.
Larger Prop does what ?
Smaller prop does what ?
Larger pitch ?
less pitch? ?

aluminum verses stainless
3 blade verses 4 blade and double stackable with 6 or 8 blades ??


Cant purchase 12 blades too see what works best for my boat

thanks

Ayuh,... Just to clarify, the 488 is a version of the 470, a 3.7l motor,...

If you in fact have a 3.0l motor, the drive ratio is too high,....

'n you Don't say what prop is on it now, nor any rpm numbers to work with,...

Prop questions are answered in the Prop forum, so I'll move this there,...

 

[Scott Danforth]

Re: What too look for when purchasing a new prop ?

start by http://forums.iboats.com/prop-questions-topics/read-first-287818.html then read

http://forums.iboats.com/prop-questions-topics/walleyeheds-prop-test-results-218877.html

However as Bondo pointed out, your model number indicates the 3.7 motor (with its heat exchanger) vs the 3.0

to increase your holeshot, you would drop down in pitch. however base on the first thread link I posted, after you verify your motor, what is your WOT? what is the current prop?

 

[alan ber]

Re: What too look for when purchasing a new prop ?

Did not realize their was a prop section
I went out too boat and got info


Brief History ,
While ago hit a bolder under water, damaged prop,
When boat was at shop mechanic said he had a spare prop put it on , give it a try it should work ?
That number was 48- 78118=17
That's when my boat started with digging in and difficult getting on plane.
I use boat once a month and stay intra coastal , with trailer and other issues I just lived with it
Now addressing this issue.

Recently came across a smaller prop which came with boat ,
I installed it during this week but did not test boat yet
that number is 78120-19

Engine is a 488 R
188 H.P
3.7 liter
stern drive gear ratio 1.84

thanks
al

 

[achris]

Re: What too look for when purchasing a new prop ?

Did not realize their was a prop section
I went out too boat and got info


Brief History ,
While ago hit a bolder under water, damaged prop,
When boat was at shop mechanic said he had a spare prop put it on , give it a try it should work ?
That number was 48- 78118=17
That's when my boat started with digging in and difficult getting on plane.
I use boat once a month and stay intra coastal , with trailer and other issues I just lived with it
Now addressing this issue.

Recently came across a smaller prop which came with boat ,
I installed it during this week but did not test boat yet
that number is 78120-19

Engine is a 488 R
188 H.P
3.7 liter
stern drive gear ratio 1.84

thanks
al

I'm sorry, but a 19" prop is BIGGER than a 17".

The first thing we need to know is what maximum revs the engine is making with the 17"... From there we can direct you to the right prop.

Chris.....

 

[jestor68]

Re: What too look for when purchasing a new prop ?

Your 1.84 gear ratio calls for more diameter.

Those 14.5 diameter props don't work well with 1.84 gear ratios. Look for props that are at least 15 inch diameter(or more).

Go to the prop section and see a number of Solas and Quicksilver props that are 15+" diameter; such as 15.5 X 17, 16 X 16, 15.5 X 18, etc.

These props will give you lots more push(static thrust) out of the hole and get you up on plane faster.

I believe the full throttle rpm range is 4000-4600 for those motors.