4.3 tb IV no fire from coil

[Slimd11]

Have no idea where to look for the drive ratio but I did notice that this isn’t the prop for this boat!!! The fin that’s above the propeller was removed because the prop would hit it I took the 19 off my 3.0 merc

 

[achris]

Have no idea where to look for the drive ratio ...

It should be next to the serial number.

... I did notice that this isn’t the prop for this boat!!!

Props aren't made 'for a boat'. They are made 'for a drive'. You find the right prop for the drive, for that boat. By checked the WOT engine rpm...

...The fin that’s above the propeller was removed because the prop would hit it I took the 19 off my 3.0 merc

The 'fin' is a sacrificial anode, and trim tab (balances steering bias). If you had a long anode and you put a later style prop then yes, they clash. Either replace the long anode with a short anode, or just file the long anode where the clash would occur. Merc released a service bulletin about that, about 30 years ago now...

Chris.......

 

[Slimd11]

I dnt see it

 

[achris]

Ok, after laying on my side, the serial numbers relate to:

Engine: 1989 4.3L (175hp, 2 bbl carb!)
Drive: 1989 Alpha 1, ratio 1.84:1

Given a 4.3L (not an LX, 205hp) that 21" IS too big for that boat. I suspect the revs you're seeing are accurate and you should move to a 17" prop. 19" if you're very lightly loaded. Put those (17" or 19") on and check your RPM with a service tacho, NOT the dash tacho!

Chris............

 

[Slimd11]

Thank you so much I appreciate all the help and the knowledge ima def go buy a 17 then

 

[Slimd11]

Can I wire a digital tact in

 

[achris]

Can I wire a digital tact in

yes.

 

[Slimd11]

Ok so I am back with an update changed propeller to a 19 still only getting 3500 rpms and 30 mph a 17 pitch was too small wouldnt plane

 

[Slimd11]

She ran hot last night while cruising and oil pressure shot up ima change impeller today

 

[79Invader]

Ok so I am back with an update changed propeller to a 19 still only getting 3500 rpms and 30 mph a 17 pitch was too small wouldnt plane

So you were hitting 4000 RPM’s and 32 MPH (gps verified) with a 21p prop, now you’re hitting 3500 RPM’s and 30 mph with a 19p... and it wouldn’t plane with a 17p....

Something is clearly not adding up.

 

[79Invader]

oil pressure shot up

What do you mean here? Oil pressure shot up while you were cruising?

 

[alldodge]

So you were hitting 4000 RPM’s and 32 MPH (gps verified) with a 21p prop, now you’re hitting 3500 RPM’s and 30 mph with a 19p... and it wouldn’t plane with a 17p....

Something is clearly not adding up.

Agree
Get another tach because the one in the boat is off
If your using the speeometer then that is also off, need a GPS or app for your phone
Do a compression test because you may also have low power

 

[79Invader]

Do a compression test because you may also have low power

agree, you need to run a compression test and an overall assessment of the health of your engine if these are your actual results.

I’m lost because planing your boat with a 17p prop compared to a 21p prop should be much easier, not harder, so even if the engine had low power, a smaller pitch prop should help it...

Think of it like putting your car if 1st gear to take off vs putting it in 5th gear to take off.

 

[Slimd11]

My carb is acting up to keep shutting off ima do the compression test and get this carb cleaned. And another problem arise it’s running hot impeller was good in one piece changed it anyway. Getting water thru the inlet hose removed thermostat still same, barely any coming from pump so ordered new pump. Also put a 19 p prop on her and she planes and end that 17 was the wrong prop it was ummm cavitation or sumthing basically spinning or