Yamaha OX66 150 maximum RPM - HELP!

[westar]

Hello all - first post here! I am purchasing a 2000 Grady White 208 Adventure with a Yamaha ox66 150 engine that has approximately 400 hours on it. The boat and engine seems great. Tomorrow, I am meeting the mobile mechanic who will do the compression check on the engine then she is ours.

However, when scheduling the time to meet with the mobile mechanic we talked a bit - he knew we were doing a sea trial today. The one thing he said I should be sure of is that the engine topped out over 5000 RPM.

We did the sea trial with 3 adults, 2 small children and a quarter tank of fuel. We had decent winds and a 1-foot chop in the bay (Sarasota).

BOTTOM LINE - We rode WOT for about 40 seconds and the engine never got over 4700 RPM.

After running at WOT and cruising a bit....I did jump in the water with a mask and closely inspect the bottom - which, is immaculate...no barnacles etc.

Is this a problem? Help!!!

 

[Parthery]

WOT of 4700 is too low. Should be closer to 5500.

What prop was on the boat? GW shipped this setup with a 13.25 x 17 SS prop, if I recall.

 

[westar]

I have no clue what prop is on the boat. Could a prop that is too large cause the low RPMs?

Is this an indication there is an underlying issue with the engine?

I doubt the current owner ever changed the prop.. He did tell me he has never driven at WOT. He usually cruises at 3000...

Is this a deal breaker?

 

[westar]

Also - I didn't touch the trim. Could the trim change total RPM?

 

[232 GULF]

Trimming up could increase RPM but not by so much that it would eliminate concern.....I'll bet the compressions are low. Be very cautious...

 

[westar]

What should normal compression be?

 

[seasick]

WOT of 4700 is too low. Should be closer to 5500.

What prop was on the boat? GW shipped this setup with a 13.25 x 17 SS prop, if I recall.

That was the size and pitch shipped with the boat but OEM prop is aluminum. The prop may be stamped 17M on the outside hub.

My 209 barely makes 5300 and has since birth
I suspect the prop could be swapped but I rarely run wot.

One thing to check is that the throttle linkage is adjusted correctly so that you get full range at the motor linkage.

 

[westar]

So if it has an aluminum prop might it be turning less RPM? I have a marine mechanic friend that swears trimming up the engine would push me to and past 5k RPM. We'll see what the compression numbers look like.

Anyone else have comments? I don't want to make an expensive mistake!

 

[westar]

Did the compression check - 130 psi on all cylinders! Mechanic said the engine was in extremely good condition. When I took the boat from the sellers dock to mine I trimmed the engine and got to 5000 RPM. Mechanic also looked at the prop and said the pitch is why it's not getting to 5500 - not something with the engine. So, looks like all turned out well.

Love the boat - incredible ride. Looking forward to many years on the water! Thanks for everyone's help.

 

[Grog]

Did your mechanic check the O2 sensor? When they start to go bad and/or fouled the motor will run lean (less power and eventually a burnt piston).

 

[fishermanaddict]

Which mounting hole on your motor ? I also have 150hp on my 209 Escape . Motor was mount on 2nd hole from top , Got 5000 rpm max. So I raise the motor up by 2 hole rpm increase to 5250 rpm.

 

[westar]

Have no clue which hole it's in. We went for a ride tonight after work...got it up to 5200 RPM. How can I tell what hole it's in?

 

[Parthery]

If you are now seeing 5200, you are in good shape.

The one thing that might be worth doing is looking for a SS prop. You will get better holeshot, may see an increase in your cruising speed, and another 100 or 200 rpm will put you closer to 5500.

Keep an eye on eBay....they pop up from time to time. You should be able to find a good deal...

 

[MaineBoy]

175

I am about to take delivery on a 99 209 with a 175HP Saltwater Series. Doing a sea trial before I take opwnership. COmpression was done and it is all fine. Should the max RPM's be in the same ballpark of 5200-5500?

 

[Parthery]

Yep...

 

[MaineBoy]

perfect - thanks -