Question for Mac and Scott

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Rob LaMoy

Well-Known Member
Mar 19, 2001
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You guys seem to be the techs of this page so here goes another question. With my '89 GT150, where does it redline, and what is a safe rpm at WOT to run? Also what is safe range that my water pressure gauge should show. It is a 0-30 psi gauge. I am replacing these and they never worked when I got the boat. I only have one weekend to break in all the new gear I have on this rig before my clients start showing up. This is the first year I have guided from a bass boat. So I want to be sure nothing is left to chance. Thanks,
Rob -

Those questions are best answered by Mac, Mini or Jim Lively......

I'm not so much of a "Boat Techie" as I am just experienced with cars, trucks and motorcycles....... Just that some of those have carry-overs to the boating world.

I'll let them take the lead in this case! But THANKS! for the compliment!

Rob,...Jim Lively is deffinetely the motor guru on this page,....i speak more from experience than actual book knowledge and technical specs!! LOL....A carburated 150 will run at higher RPM's than the newer EFI's and Opti's, but you shouldn't push one past 5800- 6000RPM's for any length of time..I ran my 150's and 200's at 5600 WOT and that's as hard as I want to run them.....I'm not a speed freak, so I'll sacrifice top end for overall ride everytime!
I fish against guys who aren't happy unless their boats do 80 mph! They will beat the hell out of their boats, equipment, partners and themselves just to get to their spots first......i'm too old for that, hurts! Your water pressure should be @ 20psi if not more. Keep your RPM's @ 200 less than red-line at WOT and your motor will thank you for that, via several more years of reliable service. Hopefully Jim will read this post and correct any "tech" stuff we might have missed or gotten wrong....good luck and have a great season!!
The specs you need for your GT150 are out of my range of brands. I have only owned Merc and Suzuki. I do know that Ev/John motors use a high pressure low volume pump. The higher the water pressure the better. Any dealer should be able to answer those questions for you, if they dont they arent worth the time....
The GT150 operating range is 5000 to 5600 RPM, which essentially means that it makes its best power in this range. Although the GT will readily climb above 5600, it is prone to blow skyhigh is pushed past that limit for more than a few seconds.

The water pressure on it should read around 10 psi at idle and then right on up to 25 or so at full throttle.

Just keep her at 5600 or below and you'll be fine.

Good luck.


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