650xs

[Roshambo]

Just recently purchases Scott Whittington's 650XS.

Now what is the correct lower unit oil to be used for these? Should I run with companies like Redline, Royal Purple, Eneos or just go with Mercury High Performance gear lube?

Also what type of fuel should I run with it and its octane? I've gotten replies like a 50/50 mix of 98 and 100, Avgas (100), 91 + catalyst additive for drag outboards.

I don't know how easy Avgas is to obtain but for now sounds like the best choice.

Please let me know your opinion.

[sam]

Use AV gas or canned race gas only in the 650XS (no low grade stuff with additives)


I'd recommend Alisyn lube in the lower unit http://forums.screamandfly.com/forum...d.php?t=110015

Might as well not pay shipping and have the best stuff

[Roshambo]

Avgas 100LL/130

I've been researching Avgas for up here and the only stuff I can get is the 100LL - Low Lead. According to petrovalue.ca where I got the info from, the 100LL/130 stuff has 0.58 grams of lead per liter where as just the 100/130 has 1.28 grams of lead per liter, but 100LL/130 has double that of lead than automotive "unleaded" gasoline.

It has a lean mixture octane rating of 99.5 and a performance number of 130 octane number. 100LL that is.

I forgot about Alisyn lube! Thanks for the reminder Sam.

What viscosity should I go for with gear lube?

I'm new to the high performance side of boating, and I'm full of questions.

[sam]

100LL is sufficient

I haven't tried Alisyn 2 stroke oil, but I have never heard any complaints

[pat]

My experience is that AV gas burns too slow. There is no way that a 650XS has enough compression to burn 130 anyway but even still you have to consider that aircraft engines are not outboards and therefore outboards are not formulated or optimized to use this fuel. I have had some success blending AV gas but it depends a lot on your engine. My recommendation would be to go with VP fuel (Marine 97 Octane). Unless your cylinder head compression is above 200psi, you won't get any performance advantage. I have built and raced EP and SST-60 engines for decades and if you don't have the engine right in terms of porting, piston-to-wall clearance, ring gap, stoke, etc, etc, no fuel in the world is going to help much.

Pat Kants

[sam]

SST-60 engines

Pretty sure the XS has higher compression than the SST-60 ... he's not looking for performance as much as not destroying the engine with today's junk gas

Exactly what grade of gas did Merc originally recommend for the 650XS?

[Popa Sam]

Here are the specs on the 700X. I think the powerhead was the same as the 650xs except for finger ports.

[bandit64061]

gas!!

Don and george had good info. on that awhile back on another forum.
I think the concensus was pumpgas on 1 side and pump av.gas on the other.
I think the jury is still out!!

Pretty sure the XS has higher compression than the SST-60 ... he's not looking for performance as much as not destroying the engine with today's junk gas

Exactly what grade of gas did Merc originally recommend for the 650XS?