Low budget OMC twin project

[sWaltsu]

Hello

this is my extremely low budget motor / boat project.

I had bought couple broken OMC motors. Old 50hp with BIG electric shifting gearcase. Second motor is 1982 60hp.

First motor (old fifty) was overheating and piston was melted. Gear case is full to water...

Second motor is better.
I will replace just piston rings, seals and gaskets.

Because motor is opened. I might lightly modify it.

change reed valves to fiber model, clean all flow path and increase cylinder compression.


cylinder holes must be modify!


exhaustpipe must be shorten

all bearings is OK. But how fast i can run it, with standard connecting rod, pistons and crankshaft?
6000RPM must be ok, but how it take over 6500RPM?
How much i dare to set ignition timing (degrees)


This just purpose to learn to get more power to propeller.

Two motor, boat and lot of building parts, was cost less than 300 USD.

any ideas what else i must do, to get more power?

Setup:

Gear case (2.4:1 ratio)


four blade "home-made" Cleaver (23")


hull without deck.

--- My other projects---

Bat 22 offshore
and
and homepages: homepages

[Fastjeff57]

Got two complete (but disassembled) 50/ 60 hp OMC power heads if you need any parts. Just pay shipping.

Jeff

[calvin]

Is there any difference between the 50 and 60 hp..or is it just prop shaft vs powerhead hp?

[Fastjeff57]

Porting! The 60 hp has far more aggressive porting.


Jeff

[calvin]

I would love to hace the 60 but need a short shaft with trim and tilt.

[Fastjeff57]

Sorry, the FREE lower unit I have for you is a long shaft.

Jeff

[sWaltsu]

Thank´s, Jeff your offer. But shipping is too difficulty.

My short shaft works only with electric gear case. that´s why i must use long shaft.

Can anybody say, how much i can take off that cylinder head.
We use 98 octane gasoline (Now it might says E10 gasoline. 10% ethanol and 90% gasoline).

And how much i can take RPM, with original crankshaft etc?

Today i get new piston rings. Tomorrow starts cylinder porting (Port and polish)

[LakeRacer99]

Thank´s, Jeff your offer. But shipping is too difficulty.

My short shaft works only with electric gear case. that´s why i must use long shaft.

I'm 98% sure you can make that short mid work with a shifting lower unit. I have both, but have not converted one, but I plan to one day if needed.

Kinda hard to jump out of the gate modifing the motor. how do you learn if you helped it or not? My favorite reply is to get it running, dialed in with available power, then start your mods-especially porting.

[sWaltsu]

Attachment 52482

Problem to use short shaft. is in the picture. part number 29.

Short shaft model is not hole to gear shaft.
Because electric gear case have only two wires.

[LakeRacer99]

Attachment 52482

Problem to use short shaft. is in the picture. part number 29.

Short shaft model is not hole to gear shaft.
Because electric gear case have only two wires.

I can't see your attachments...I remember thinking it would not be hard to add the hole. much easier than finding a short mid.