85hp charger speed/prop/rpm concerns

[jimmbo]

Being that the Props you are using appear to have little or no Cup, there a very good chance that having the Engine at that Height, is the reason you are experiencing the Prop losing its bite.

 

[Guy707hc]

Now you have me wondering how much to cut out and reinforce/re-cap... something I don't want to just try to see if it works.. I was understanding within an inch was ok. Maybe just up to an inch lower or flush?

 

[jimmbo]

Unless you are exceeding 45 most of the Time, Normal Duty is probably the Best Choice for your Boat, but you might have to even put it a 1/2" below the Hull.

 

[jerryjerry05]

The pics of the props show both are cupped.
I had twin 88/85 Forces Replaced with new because I thought they needed to be cupped. Both new props were exactly the same as the ones I already had. The cups built in.

 

[Guy707hc]

I don't want or need any speed. I fish mostly walleye and perch. The biggest body of water I fish is 800 acres. No speed restrictions but not needed for me. I can cross the entire in 1 or 2 minutes @ 30mph. That is plenty of speed for me. I would like to I install the 19p prop and have another go at it since I have repaired some running issues(fuel pump, carbs, tach, and now my primer bulb sucked up the ball into the top and wasn't letting barley a trickle of fuel to the pump) it will act a little different and want an accurate test before I cut the transom down.
Jimmbo thank you for the illustrations they are clear and having all positions on the same document helps alot to understand.
Jerryjerry05 it is hard to tell from the photos but you are right, there is a little cup to both props.. not alot but some..

 

[jimmbo]

The pics of the props show both are cupped.
I had twin 88/85 Forces Replaced with new because I thought they needed to be cupped. Both new props were exactly the same as the ones I already had. The cups built in.

If there is a Cup on either of them, it is pretty much invisible

 

[jerryjerry05]

Thats what I thought when I spent $250 for new "cupped" props.

 

[jimmbo]

Thats what I thought when I spent $250 for new "cupped" props.

$250... That is Pocket Change for a Prop, all 3 of mine have a List Price of over a Grand each

 

[Guy707hc]

Guys 1000.00 for a prop! Ouch.. ya I thought 250 was salty tasting! I bought a used prop from ebay for 50.00 shipped just incase the boat hated it. Which it did... atleast till I lower the unit to the hull when parallel.
I'm looking in to a plate to use the existing mounting holes in the transom to set the motor back 5" and down 1". The holes are only an inch above the water line and I don't want them sitting in water if they don't have to be. I will give the 19p another go before I do anything. Busy schedule for me with events and plans. But I will have it out again in a few weeks to post results.

 

[jimmbo]

Just setting the Engine further behind the Transom/Boat, is equal to lowering it.
As for the Lower Holes in the Transom, they will be even lower when the Motor is mounted on a Bracket, as the Motor's weight is leveraged. Properly sealed they would not be a Problem in any configuration

 

[Guy707hc]

Just setting the Engine further behind the Transom/Boat, is equal to lowering it.
As for the Lower Holes in the Transom, they will be even lower when the Motor is mounted on a Bracket, as the Motor's weight is leveraged. Properly sealed they would not be a Problem in any configuration

I researching this and then seen you posted.
I actually have a close friend who is a machinist and would like to come over and take some measurements over a few drinks. We have researched what is avaliable on the market and he thinks we will be ahead to make one from quality aluminum. He suggested making the plate that mates to the boat larger to handle the added load from adding to the fulcrum/leverage further from Transom. But I think we can have a larger plate to spread/support more load, just have the new plate drilled to match existing holes in the transom. He wants to have the back plate that the motor mounts to, be pre drilled to have a couple inches of adjustment in 1/2" increments.
That's the plan. For now I will get us some solid numbers with the 19p. And a properly calibrated tach. Thanks again