Crossflow build

**Fastbass88** · 08-30-2019, 12:25 PM

Hi all, been browsing the forum and seen lots of great info, wondering if someone could lend some advice.

Boat is a 15.5ft hydrasport veestar 90, does have a pad.

Current engine is a '87 Johnson 88. I also have a '73 Evinrude 115 and '76 Evinrude 135 (no lower or power pack on 135).

Want more ponies out of the 88, one cylinder is a bit low so was going to open it up anyway. Not sure of the condition of the 135 block but options right now are to port the 88 using the 135 specs, or swap power heads if the 135 is usable.

What would my best options be with the parts I have? Anyone have porting measurements? Don't want a full 9 page motor but a lake runner that could ideally get me to 60mph+ at 6000rpm.

**powerabout** · 08-30-2019, 06:29 PM

the powerhead wont bolt up due to 2 of the front studs being in a different place
the 135 has great heads but you will need good fuel

**Dave S** · 08-30-2019, 06:33 PM

Best Bet.... save ya self lots of work.....get a V6 150 merc ....Cheep .... common..... and ya can get parts for them....And they will blow the old stuff ya have out of the water.....I see ya up North.....and things may be harder to find....go for a ride....JMO........

**Fastbass88** · 08-30-2019, 07:03 PM

Thanks. I've been doing a ton of research and always find conflicting info. For example 115 and 135 crossflow have the same porting (different heads/exhaust/etc). My 88 is the old 115 since it's post prop rated hp. Guess I won't know until I open them up. Plan is to run 91oct.

Plan so far
-use 135 heads, carbs, bubble exhaust on 88.
-port and widen with 5/8 corners the 88 to the 135 specs
-keep the 88 coils
-throw a 23p prop on and see what it does after getting Jetting dialed.

Any better way to do it with what I have? Is dropping the bottom of the exhaust port advisable, such as in the 9 pages?

Boat parts are scarce here. Also a v6 Merc would weigh almost 100lbs more then the 88. I'm keeping this on a diet, also thought about a looper but similar weight penalty.

**FMP** · 08-30-2019, 07:04 PM

Looper 140, then start the game.

**powerabout** · 08-30-2019, 07:19 PM

Originally Posted by FMP

Looper 140, then start the game.

Same weight as a v6 merc

**FMP** · 08-30-2019, 07:27 PM

I'll take your word for it but thought less by enough.
So a looper v4 is about a hundred more than an X flow?

Wow , big bore with big lu 368. Must have been thinking earlier version.

**Fastbass88** · 08-30-2019, 08:02 PM

I originally was thinking 140 looper if I could find one until I found out how heavy it was. I'm thinking if an old 90hp can push it low 50s, a massaged 135(130ish prop) could be in the 60s setup right. Not to mention higher cruising speed which would be used often heading to fishing spots.

**Forkin' Crazy** · 08-30-2019, 08:28 PM

Originally Posted by powerabout

Same weight as a v6 merc

A V4 looper is 400#s? Hell an old school 235 is lighter than that. And as fast or faster than a Merc 200.

**Forkin' Crazy** · 08-30-2019, 08:46 PM

Originally Posted by Fastbass88

Hi all, been browsing the forum and seen lots of great info, wondering if someone could lend some advice.

Boat is a 15.5ft hydrasport veestar 90, does have a pad.

Current engine is a '87 Johnson 88. I also have a '73 Evinrude 115 and '76 Evinrude 135 (no lower or power pack on 135).

Want more ponies out of the 88, one cylinder is a bit low so was going to open it up anyway. Not sure of the condition of the 135 block but options right now are to port the 88 using the 135 specs, or swap power heads if the 135 is usable.

What would my best options be with the parts I have? Anyone have porting measurements? Don't want a full 9 page motor but a lake runner that could ideally get me to 60mph+ at 6000rpm.

Find a 79 or newer 140 and build a drop on. Keep the 88 for a spare for when you blow it up.

79 up has the same linkage. 78 down no.

In 87 they started rating HP at the prop instead of the flywheel. So you really have a low compression 115 or 100. I think the 87 up 115s were the old 140 with looser heads.

Some one will be along in a minute to tell me how wrong I am or agree with me, one or the other!!! LMAO!!!

The heads in 79 and 80 will probably be good enough. Premium fuel ONLY!!! I am more of a V6 Xflow guy. But I assume they were like that because right after 80 on the V6s they started loosening the heads or adding thicker head gaskets because of the crappy gas. No one wanted to pay for premium.

**FMP** · 08-30-2019, 09:57 PM

Chrysler ! Ha!!! Didn't expect that, did you!

**MattGreen** · 08-30-2019, 10:01 PM

Please update your location so Canadian S&F members can perhaps help more. Crossflow V4 parts are plentiful in Canada if you look in the right places.

The 135 heads are the tightest non-race V4 heads available and will work great if you use enough octane but I caution that 91 with proper timing is probably NOT enough; try Sunoco or Chevron 93/94.

To to make the ‘88 work well you actually need the bubble-back exhaust housing from the old 140s/later 115s. The turtle-back 135 is not the same. Overall Forkin is pointing you in the right direction.

Matt

**FMP** · 08-30-2019, 10:08 PM

I would think fresh 91 Shell will do the job with lots of good oil and proper tuning.

**Dave S** · 08-31-2019, 01:05 AM

I saw a 140 bubbaback in the scrappy yard.....too lazy to pull it out.......

**Fastbass88** · 08-31-2019, 08:26 AM

Thanks for the info guys, been scouring the net enough to make my head spin.

I'm from southern MB. I'll keep my eyes open for an old 140 but will also buy a lottery ticket. Im all for someone nearby that has stuff laying around!

Can I adapt the 135 carbs on the 88? As in swap the carbs but use the newer linkage system from the 88? Was hoping the ports wouldn't be to far off the 135 and use the 135 exhaust. I read it's not as good as the 140(smaller channels?) but still could be used? Thanks again for the help!