Engine compatibility

[FastFisher88]

Hi all,

Found this forum recently and seen a wealth of knowledge. Not new to boating but have little knowledge in the outboard sector.

Picked up a boat with an 1987 Johnson 88 spl paired to a 1986? Hydrasports veestar 90. Runs like a top, GPS said 40mph at a touch over 6000rpm with 13x19p. Also has hydra foil installed that I was going to remove. Was going to try to find a 21p to get some more mph and get to rated rpm.

My question is i have a 1973 evinrude 115 starflite sitting around. Do both engines have the same block? Was thinking of swapping blocks if the porting was that of the 115-140 horse engines and getting more hp out of the 88 setup with changing exhaust, intake, 140 heads, etc.

Am I barking up the wrong tree? Modding/thinkering is how I spend my spare time. Can't help myself.

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[racerone]

Look at the part # for the gasket between the engine and the exhaust housing.-------That will tell you the story.-----I think you will be disappointed !

 

[jimmbo]

First of all, your numbers don't add up, if you were turning 6000 with a 19 in prop you would be getting over 50 mph. At 5000 you would be going over 40 mph. Perhaps your tach is off, or your engine is mounted so high you have a massive amount of slippage

While your 88 and the 73 115 have the same displacement, doesn't mean the blocks will interchange. in 74 OMC made some major changes to the block. Then in the late 70s the midsection was changed

The 115 came in Crank Rated versions and Prop Rated versions, depending on the vintage. Some will claim the Prop rated 115 is the crank rated 140 with a Decal Change. Maybe, maybe not. One would have to go thru Original Parts listings to find the differences

The lower hp V4s can often be hopped up to 115, or 140, with some machining, and/or parts changes. It is easier and often cheaper just to get a higher hp motor to start with

 

[FastFisher88]

Much thanks for the input. I Beleive the prop has been repaired so I'm not sure on the true specs on it dispite the 13x19p stamp. I was going to replace the tach as it was bouncing once in a while but the lowest number was 6000 when WOT. Used to have a 1990 Johnson 115 so am familiar to higher rpm sound. Anti cav plate is couple inches higher then bottom of hull but cant mount it any lower. Next step is to get a different prop, remove hydrofoil and attach functioning tach.

Also have a lead on a 1990ish Johnson 140. If I can get it for a steal I'll go that route. The one thing I defiently don't want to do is mess with porting, hence the want for a block with factory porting for 140hp.

Main goal is to crack 60mph in perfect conditions, but will be satisfied once it hits 55. Long cruising will be around 30-35.

 

[jimmbo]

A 1990ish 140 is a totally different engine. It a Looper, while the 88 and 115 are crossflows

 

[FastFisher88]

Thanks for that, always good to know! Well if it's in good shape I could just swap the whole thing. I just measured the cav plate and it's 1in higher then the hull, but it can't be mounted any lower. I'd have to measure the 140 to see if itd work on my platform anyway. Weight wise they'd weigh similar (current 88 vs '90 140)?

 

[jimmbo]

The V4 Loopers weigh about 50 - 90 lbs more than the V4 Crossflows, depending on the year of the crossflow

 

[FastFisher88]

From my research the direct swap would increase approx 60lbs. Turns out both are 20in length so that would match. Would they use the same steering/tilt/controls system so I could just swap the outboard portion? The 140 is a 1989. Also what's the average price of a 1987 88 spl vs 1989 140? Thinking how much I'd be out buying the 140 and selling the 88.

 

[FastFisher88]

Went through my current 88 spl some more, found the rectifier to have a burnt wire. Before that I was testing the tach with an photo tach and believe the boat tach was about 500rpm high(not sure since boat tach wasn't jumping around, just shift up 400rpm here, down 1000 there). Didn't have the correct bolts to pull the flywheel so havent got to look at the stator yet. Compression test yielded one low cylinder. #1-125 #2-120 #3-130 #4-110. Decarbing might help, head gasket shows seeping on outside on #2&4 bank.

Before throwing to much money into this unit, i found a 140 looper whole unit without controls for $500, and the power head from a 1976 135 for $125. im leaning toward getting the 135 since its same weight but as mentioned the mids had some differences? Could i direct swap just the 135 power head to my 88 spl mid/bottom? It has the bigger ports, heads, exhaust, carbs etc i want i believe.

 

[FastFisher88]

Sorry, finally found a thread on exactly was I was thinking on doing with the 76 135. Crank splines won't match but can use everything else, including using the ports to template the 88 spl block. Will measure everything up to make sure clearances are in spec, thinking new rings if it checks out won't hurt.

My only concern now with the 135 heads is can I still run 87oct safely? Or will I need to run 91 or mix it somewhere in between? I'll probably run it at 40:1 dyno oil to be on the safe side. Doubt using synthetic oil in this dinosaur would be worth it. I'm at about 1000ft elevation.

 

[racerone]

??----Here I thought the 76 model 135 HP had the same crankshaft splines as the 87 model 88 HP.-----Are you positive they are different ??

 

[FastFisher88]

The sticky in the top secret list doesn't include the 76, and the thread I found he said it wouldn't work? He was using a 76 135hp donor on a 89 90hp. He used everything except the crank/block/pistons. 135 block was used to measure porting. Said it was worth the hassle of you don't mind getting your hands dirty!

"In any case, I just bought a seized '76 135hp engine for parts (carbs, heads, bubbleback) and for porting measurements. I know the crank splines don't match to those of '89 but the engine was dirt cheap and I'm not planning to use the block/crank anyway."

 

[racerone]

Crank splines are the same.----Post pictures if you like.

 

[FastFisher88]

Good to know, thanks. More options are always nice. Is there anything electronic wise worth swapping over? 135 doesn't have its power pack so will probably use the 88 ignition.

Can I upgrade the rectifier or install a regulator for some more charging? Not sure if the 135 is 6 or 12 amp but the 88 is 6amp. Guessing a stator upgrade would be needed as well.