Wat do i have and will it spin up on light hull

**Keaten** · 11-19-2017, 02:30 PM

1990 evinrude 150XP i want to go through it and clean up some areas do hone job and forged pistions,, but first wat liter is this engine and wats max timing need to be set at 25? And can i shave heads to achieve 150psi carb main jet size can someone help me with wat to do or wat not to do ..light hull wanting to spin it to 7000-8500 no bottom end is ok for my setup...

**Keaten** · 11-19-2017, 02:37 PM

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**Bullet 20cc** · 11-19-2017, 08:21 PM

I can't help you out much...can only answer one of your questions. It's a 149.4 cubic inch block which translate to 2.45L. Bore is 3.5", stroke is 2.58" which is kinda short so I would imagine it could take some rpm but it's timed at a 5000 rpm redline from the factory. I'm clueless on jetting, timing and how high they can be spun...

**Bullet 20cc** · 11-19-2017, 08:22 PM

Double posted on me...

**Keaten** · 11-19-2017, 08:56 PM

Ok that helps thank you Bullet, I need some info now on the port timing changes that can be made or if they even can. And maybe some possibilities on the electronics

**faztbullet** · 11-19-2017, 10:08 PM

Shaving heads does not add compression ,just pistons banging into top of head. You tighten compression by using tighter heads.Stay with a cast piston and you'll need to ditch the CDI pack as rev limit is 5800rpm

**FMP** · 11-19-2017, 10:13 PM

What's the clearance now?

**Keaten** · 11-20-2017, 08:13 AM

Stock engine all i know ,clearance? Is that like saying wats compression now or piston to head distance? Thanks it's in storage away from me.. going to get it sometime soon..

**FMP** · 11-20-2017, 08:47 AM

Piston to head tdc, squish band tightest spot usually. Get some solder and loop it in there through the plug hole , turn motor by hand squish solder , measure the dent in the solder.
If shaving the head any amount causes contact when running then things must be tight in there from the factory.

**frank jackson** · 11-20-2017, 10:33 AM

the stock form 150 gt xp where good motors from the factory ...... you want more ? the easiest is to go find a 200/225 looper . It will be much more dependable and cheaper in the long run . Mods can be done lots of work and time and $$

**Keaten** · 11-20-2017, 11:07 AM

I can't leave nothing stock ive got to have a project i enjoy learning as much as i can about HP mods and love the satisfactory of saying yes i did that and getting reworded with the seat of pants difference. .

**racervboat** · 11-20-2017, 05:43 PM

You will find out that it already has low comp heads if they are factory and the ign system is only 2-3 yrs only .No bubble back exhaust either only on the 175hp and the adapter plate totally different from 175hp.8500 rpm good luck with that.Try for 7000 and check out the thread now going on 85hp omc v-4 build by spy bot same as your motor but 2 cyls less. What is your light hull by the way?

**faztbullet** · 11-22-2017, 07:28 AM

What's the clearance now?

Doesn't matter as on crossflows you use heads with larger deflectors in combustion area... that causes smaller cc area and compression increases...

**racer** · 11-23-2017, 07:30 AM

Actually it does because you can mill some of the heads up to .030 with no issue hitting. You can mill any of the heads but they need to be cut inside to maintain a minimum of .040 clearance. Some of these heads don't flow very well so you are wasting time and better off with heads that have a larger deflector.