Prop help 1978 200 ccp, 1988 evinrude 175

[kaptainkoz]

Hello,
I have a basic 1978 200ccp (no tee top or heavier equiptment) with a 1988 Evinrude 175. I just got the motor this season. It seems like the motor is straining and a bit bogged down in the upper rpms. twice the motor came to what seemed like a catastropic clanking stall at near full throttle only to start right back up a minute or two later. It is spordaic... I ran 30 mins straight with 4 passengers with no problem, to the next day having stall number 2 in 1/4 of the distance. Im running a 14 1/2 by 18 prop. Is this prop too aggressive leading to engine strain? I must confess that my waring alarm is broken so I dont know if it is a vacuum problem with the fuel delivery. I dont think she is overheating because I have a temp gauge and she is running between 116 and 125. New water pump. New tstats. New head gaskets. I am installing a new alarm tomorrow but i figured id throw the prop question out there to see if I can rule this out. Thanks

[Marcq]

What is your max rpm at WOT

Marc..

[kaptainkoz]

I dont have a tach. I dont want one. I am going to install a temporary one for the purpose of diagnosing this issue, however I can tell you that I am sure the motor is running labored in the higher rpms or under the strain of wind or tides. A tach may tell me whats going on at WOT but i know something is going on in the interim... either too much prop or not enough fuel at the higher rpms. I was hoping to get a baseline opinion  on prop size for my boat.

[Marcq]

Without an RPM, it's almost impossible to find the right prop for your Evinrude and at the same time making your engine happy

Marc..

[MarshMarlowe196]

I dont have a tach. I dont want one. I am going to install a temporary one for the purpose of diagnosing this issue, however I can tell you that I am sure the motor is running labored in the higher rpms or under the strain of wind or tides. A tach may tell me whats going on at WOT but i know something is going on in the interim... either too much prop or not enough fuel at the higher rpms. I was hoping to get a baseline opinion  on prop size for my boat.

Your engine stalling is probably not due to the prop size.  If it was just the strain of turning too much prop, it would probably just bog sluggishly while you're running, but shouldn't stall unless it overheated (unlikely), but you're saying it hasn't overheated.  If I were you, I'd try to find out whats wrong with the engine that's making it stall sporadically.  Once that engine is running happy, You may not need a new prop at all.

[GoneFission]

Could be a lubrication problem.  Are you running VRO or premix oil/gas mixture?  I've seen engines make noise and almost seize with lubrication issues.  If you are running premix, what ratio are you using?  What kind of oil?

[kaptainkoz]

Im running NON vro. I mix my own premix 50:1 with a penzoil or other mid grade tc3 premix. I used a graduated premix container to keep my mixes accurate. I have rigged a makeshift tach and have replaced the warning buzzer. I bungee'd a tach to the dash, powered it through the cigarette lighter, and attached male/female plug ends to the grey tach sending wire. I am leaning more towards a fuel delivery problem in the higher rpms. The general opinion I have recieved so far is that a 14.5 - 18 prop is typical for my boat. I hope to run her tomorrow with the expectations of a high speed warning buzzer from the vacuum switch. Thats my guess. I am still open to opinions about the prop size. is anyone else running a 14.5-18 on a 20' center console with an 80's/early 90's evinrude/johnson 150/175?

[bdtsr]

To much prop Koz. Most you should have on there is a 17 pitch. Older crossflow engines were not big on torque. Just ran a 20 Mako (much less V in the hull) with a 19 pitch on a 1983 150 Johnny and got 4800rpm. This is a good running motor and pulled out of the hole well. Try a 15 or 17 pitch 3 blade WITH a tach. Your motor should around 5500rpm when dialed in. How's the compression on your motor?

[hwsiii]

Koz, I can't imagine anyone saying they don't want a tachometer on a boat, even if it was only 14' long with a 20 horsepower motor. Your motor is the heart of your boat, having a tach on board can let you diagnose many boat and motor related problems, whereas without one you are roaming around in the dark. Without a tach you have no idea if you have the correct prop on your boat or you are lugging the engine and creating premature failure. A tach can tell you if you have not only the correct pitch of prop, but how efficient that particular make and model of prop works with your boat and motor combination. Props with the exact same diameter and pitch can have as much as 600 RPM difference or more between each other on a particular boat. It will let you determine the amount of prop slip difference between any two props and therefore which one might be better under certain circumstances. With a tach you can tell when your motor has started running poorly and you need to see what the problem is. With a tach you can see the difference between the cruising speeds at different RPM between any two props you put on your boat.
I felt I just had to post this because people don't need to think that you don't have one so why do they need one. There is NO acceptable reason to NOT have a tach on a boat if you plan on taking reasonable care of your boat and motor. A tach usually is the cheapest investment on your boat to determine motor health.


H