Yamaha ProV 150 Hop-up

Hi Randy, I’ve been looking through your articles on HST/ Yamaha setup. I'm running an 87 ProV 150 and would like to know if I can use those buildup tips on this motor. Setup -- 20 Bumblebee bassboat. Motor has 200 carbs and reeds, 225 heads, HydroTec tuner (not sure which one), solid mounts. Timing is set @ 22 degrees.  I have also opened up the cowl a little for more air, nothing major though. This boat is pretty heavy and turning a worked 27M prop at 5800-6000 rpm. Gps is 67 mph. Setback is 12 inches and propshaft is 2 3/8 below the pad.  I realize I'm going to have to do some port work but is there anything else that can be done?  Thinking of cutting the heads to get to 140 psi. Are the 220 and 225 heads much different? How much should I cut to get the above compression? What is the max psi  I can run with pump gas (92 octane)? Lots of questions but you seem to be one of the few Yammi gurus out there. If I can get this setup to mid 70’s I would be happy (for now, haha).

Thanks in advance,

Jim Lamb
West Columbia, SC

Jim:

Have the motor ported to1985-86 spec. Run the 220 heads as they are the best heads. The part number prefix is 6G7. Do not cut the 225 heads as they will cause detonation and failed motor. The stock 220 - 225 tuner works better on a boat like yours and pulls harder to 6500 rpm. I've run 220 heads cut .050", but that is the limit on pump gas. The 220 or 200 carbs (34mm and 32mm) run about the same. Don't have the motor overported. Stick with the stock 220 spec. You need all the low end torque you can get on your boat style. 70-75 should be easy. I've got heavy old Rangers running 70 plus with a 220 spec 150.

Randy

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

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