How can I make my boat a little faster?

**Jim Speros** · 02-04-2023, 07:49 PM

Is it possible the top drain screw got changed? Does it hit bearing near water pump base if too long?

Also the early inline gearcases had a cam to actuate the clutch dog. They can be tricky to align shift shafts properly when installing gearcase. If its wrong it will stay in forward irregardless of where shift linkage is moved. Shift issue will not bind it though.

**FMP** · 02-04-2023, 08:54 PM

It's in gear, you can't turn the prop either way? Will the flywheel turn?

**Spaceman Spiff** · 02-04-2023, 09:25 PM

Originally Posted by Jim Speros

You should not force the shift linkage when the engine is not running. If engine is off you should spin prop shaft by hand while moving linkage.

I hope David's suggestion got you moving in the right direction.

I've got to give you credit for your ambition. When you get it together please share a pic of the lower unit in relation to bottom of boat to show water intake.

Thanks. I'm thinking about cutting away the splashwell and peeling the glass off of the transom. And then laminating a piece of 3/4" marine ply in front of the transom to the full height of the gunwales: 22". And then essentially filling in the remaining above the existing transom with epoxy and glass mat to match the new piece. Won't really need a splashwell with 22" transom anyway. Or I could make the center of the transom even higher or add a jack plate to it. I'd really rather use the long shaft motor anyway due to the prop choices. I already have 13, 15, 17, 19 and 21" pitch prop for the 70hp. But, if the right 20" transom boat pops up in the meantime, I may just go that route. But it has to be 13 or 14'.

Thanks to you all, I'm excited about the my newfound knowledge of how important the motor height is. Just one more thing for me to obsess over with my future boat projects. LOL I do appreciate all the help.

Stephen

**Spaceman Spiff** · 02-04-2023, 10:21 PM

Well, I think David was spot on. I pulled the pump cover and put it back and now it spins like it should. Hope to give it a run tomorrow.

**Spaceman Spiff** · 02-04-2023, 10:28 PM

Looks to be 3 1/2"

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**Jim Speros** · 02-04-2023, 10:55 PM

Keep an eye on your water pressure. If the prop will bite I think you'll be surprised with how it acts. That height looks about what you want. If the water pressure drops off you can try tapping and plugging top few holes on each side of intake. I think 1/16 pipe plug fits those holes well.
If you can get water pressure stable I'm guessing about 15 lbs and a prop that while bite you will be on a worthy path.
What did your pressure gauge used to read? I'm not sure what water pressure that engine needs. Maybe someone else knows and will share.

**FMP** · 02-04-2023, 11:43 PM

Might want to plug the top holes . Think it might get +20lbs at high speed?

**Spaceman Spiff** · 02-05-2023, 12:36 AM

It should run about 5 at idle and 15 at WOT.

**David - WI** · 02-05-2023, 01:34 AM

Aluminum is weak compared to stainless steel, so the blades have to be thicker in order to not snap off.
The thicker blades are like standing waist deep at the beach and swinging a baseball bat into the water versus swinging a katana.

The horsepower wasted plowing water is horsepower that's not moving you forward.

**FMP** · 02-05-2023, 12:15 PM

So with a 10x14 Aluminum it's turning 5k at that height ?

**Spaceman Spiff** · 02-05-2023, 02:12 PM

Originally Posted by FMP

So with a 10x14 Aluminum it's turning 5k at that height ?

At the original height it was turning 5000. I'm heading out shortly

**Spaceman Spiff** · 02-05-2023, 04:37 PM

Well, I covered up the top two water inlet holes and had no problem at all with the pressure. However, it was venting pretty good right off the get go. Only got it up to 26 and rpm was spiking over 6K. Exactly like driving a car with a slipping clutch. So should a put a anti-vent plate on there or trim an inch off the motor board? Or both?

**Jim Speros** · 02-05-2023, 04:57 PM

Best first move is a bigger pitch prop. Are the other props you have the same barrel size? If pressure is good try to be patient and work thru some props before you go trimming transom. You would benefit finding a prop with more rake. Rake adds holding power to a prop. It is the measure of the angle the blades angle back.
DO you have a local prop shop in town? Go make friends with them. Or call the guy suggested earlier in the thread.