Octane
 

Can anyone tell me if it is okay to run 89 octane in a pair of HP 500's.

It lists recommended octane on the spark arrestor. I think they will eat 87 if I remember correctly.

87 is all they need ortherwise you get a lot of black soot on the transom

87 is fine. 89 is better if you can get it.

not only is it fine, they re made for 87

Anything higher than 87, you will have a black transom and less hp. The higher the octane the harder the fuel is to burn, so when you have unburnt fuel in the combustion camber is never working properly witch drops the HP.

The black soot is from them being jetted "PIG" fat. Lean her out a few numbers and hang on! The ol' black engines come to life taking a bit a fuel out of them. :D

Yes lean them out and advance the timing to 36degree and run 87/89 octane. My HP500 and a lot of the F1 guys ran them this way.

Dean,

Just how many "numbers" do you recommend from the factory sizes?

Thanks.
Mark

octane
 

To everyone who replied to my question on octane, thanks for the replies they were very helpful, sorry that it took so long to reply but computers are not my strongpoint.

I wish I could find 87 on the water. The lowest I see is always 89.

Would anybody be interested to rent an octane test tool to measure gas in your boat or at your marinas pump. I'm interested to buy a scan tool for $ 10K to see what I have and how fast it goes bad, cheaper than killing an engine. But I would also like to pay for this thing ? Tool will test octane with up to 15% ethanol -rent will have to be at least a couple hundred bucks + shipping to make this cost effective

they run 87 octane, but i always use 89 cause gasoline loose's it octane some after sitting for a few weeks, so say you fill your boat with 87, you dont use it much that day and it sits a couple weeks, then you put it in the water, well now the octane might be down 1 to 3 points, something to think about!!

Nice thought for at the pump, real time insurance... We could be interested in same.

I have wondered why we cannot have an environmentally friendly dip test strip for octane rating...

oops, because of the chemists?? sorry just kidding!!!

Yep just run 87 in them, they are built for it and run just fine. No more power with 93 unless you have increased the compression ratio or you advance the timing a lot and are hearing a knock.