Performance Tips

[andrew j cox]

Hi Guys, I have a 77 V4 85HP on my boat, are there any performance tips for these old V4s to ring a bit more power from them, simple bolt on stuff etc

 

[Bosunsmate]

Not sure about performance tips, prop changes can change operating performance.
Reliability wise you really should do this
http://forums.iboats.com/forum/engi...aq/228380-johnson-evinrude-adding-a-tell-tale

 

[Faztbullet]

That's a small bore (3.375) motor and not much you can do to "hop" it up other than get boat/motor set up best as possible. Remember that a powerhead rated motor and is only about 80hp at prop

 

[emdsapmgr]

Since it's a small bore block, you won't be able to find any higher compression heads. The stock ones should yield about 125 lbs-still decent compression when compared to the last crossflows made- which were in the 90's. They will be ok. With your engine, you should be able to install a set of 1 5/16" carbs, perhaps from an older 135 crossflow. They'll bolt right on. Also, add the 4 rubber intake filler blocks from a 79 140 hp engine. They'll add 3-5 hp. Are NLA, but you can still find them. If you want to pull the powerhead apart, you can square off the intake and exhaust ports-improving the breathing capability quite a bit. You should expect you'll have to lean the carbs out somewhat, as they will overfuel your block-depending on what you do to it. A set of composite reeds will improve the idling and midrange, maybe 100-200 rpm's on top.

 

[dropbear68]

Thanks guys some good food for thought there, sounds like I need to find some outboard wreckers and round up some bits, my eventual plan is to find an old 135 and rebuild it, I had one of these old 85s but a much older version late 60s johnson version with the same hydro elec box I had it screwed onto a little 15 footer and it was a freak geez it went quick, I like the reliability of the old V4s and there still plenty earning there keep, there are several 115s locally that are very cheap but there just power heads and I never trust anyone who says yep shes a good motor mate and they only want 100 bux for it, I smell rats from a long way off lol

 

[dropbear68]

Since it's a small bore block, you won't be able to find any higher compression heads. The stock ones should yield about 125 lbs-still decent compression when compared to the last crossflows made- which were in the 90's. They will be ok. With your engine, you should be able to install a set of 1 5/16" carbs, perhaps from an older 135 crossflow. They'll bolt right on. Also, add the 4 rubber intake filler blocks from a 79 140 hp engine. They'll add 3-5 hp. Are NLA, but you can still find them. If you want to pull the powerhead apart, you can square off the intake and exhaust ports-improving the breathing capability quite a bit. You should expect you'll have to lean the carbs out somewhat, as they will overfuel your block-depending on what you do to it. A set of composite reeds will improve the idling and midrange, maybe 100-200 rpm's on top.

In regards to higher compression heads the stock items cant be shaved to boost comp?

 

[emdsapmgr]

These crossflows use domed pistons. I'd be careful when considering shaving these heads. If shaved too much, the pistons (domes) could hit the heads when re-installed. It won't take much shaving to wind up with a set of junk heads. Your heads will make plenty of hp the way they are.