1987 erude 88 SPL

[dieselcat]

I have a 1996 Landau Pro 17 Aluminum Bass Boat.I currently have a Michigan Wheel Apollo SS prop,13.125X19P.I asked in johnyrude forum about what WOT rpm's are supposed to be for this 88 and 5500-6000 is the answer i got.With prop i have now I'm only getting 4600-4700 rpm's.I checked on Prop Wizard before i installed the prop and it told me either 19P for good all around performance or 21P for top speed.Originally bought this prop for my 75 hp merc,so instead of buying new prop i just bought a new hub kit.Checked also to make sure prop would work with the erude and they where same except the hub.

 

[Silvertip]

Re: 1987 erude 88 SPL

So what is your question? I can tell you that the 19P is correct for a 75 Merc but the Merc has a 2.33:1 gear set whereas the Johnny/Rudes have a 2:1 gearset. However the extra 13 HP should allow spinning the 19P just fine. I would look at the throttle adjustments to make sure the butterflies in the carb are perfectly horizontal with the throttle wide open (engine not running of course). Then make sure the engine is actually running properly and that the setup is correct. By setup we mean engine height adjustment (not trim) which places the antiventilation plate an inch or so above the bottom of the boat as a starting point.

 

[hwsiii]

Re: 1987 erude 88 SPL

Diesel, I have an apollo as well and i love it for my purposes. If you will buy the 13 1/4 X 15 you will be turning about 5,600 RPM and doing about 35 MPH. That should work fine for you.

H

 

[dieselcat]

Re: 1987 erude 88 SPL

Right now at 4600 rpm i get 44 mph measured by gps,I'll go back to the merc before i would sacrifice 10mph.How ever i don't think it will come to that,i think i have a timing issue that is not allowing me to get max rpm.Going to take to shop for a link and sinc then go from there after i know it's up to par.

 

[hwsiii]

Re: 1987 erude 88 SPL

I will just tell you that your motor is lugging VERY bad, and it will take its toll on it. Good Luck. I hope that is the problem.

H

 

[dieselcat]

Re: 1987 erude 88 SPL

So what is your question? I can tell you that the 19P is correct for a 75 Merc but the Merc has a 2.33:1 gear set whereas the Johnny/Rudes have a 2:1 gearset. However the extra 13 HP should allow spinning the 19P just fine. I would look at the throttle adjustments to make sure the butterflies in the carb are perfectly horizontal with the throttle wide open (engine not running of course). Then make sure the engine is actually running properly and that the setup is correct. By setup we mean engine height adjustment (not trim) which places the antiventilation plate an inch or so above the bottom of the boat as a starting point.

Butterflies are perfect did that before i even took the motor out,Basically i was just wanting to know if the info from the prop wizard was accurate?There is no reason i should have to go to a 15P prop to get rpms up,have a friend with 20ft aluminum all weld boat with 90hp vro [which mine is the same motor minus the vro]and 17P prop and he turns 5600-5700 WOT,My boat is quite a bit lighter so i would only assume 19P should be no problem for my setup?

As far the antiventilation plate i will have to double check but i think it's dead even with the bottom or maybe even a little lower.Should i try raising the motor up 1 hole?And what would i gain/lose by doing this?

 

[hwsiii]

Re: 1987 erude 88 SPL

If you had an aluminum prop at 19" pitch, that would be true. But you do not, it is running negative slip numbers which show it is more than a 19" prop. They do not make a prop that runs negative slip numbers, so that means the prop is more than a 19" Pitch.

H

 

[Tacklewasher]

Re: 1987 erude 88 SPL

As far the antiventilation plate i will have to double check but i think it's dead even with the bottom or maybe even a little lower.Should i try raising the motor up 1 hole?And what would i gain/lose by doing this?

First, I was going to post what hwsii did. Something is wrong with your number. Whether your tach is off or you have the prop pitch wrong, something is wrong.

As for raising the motor, if you go too high your prop will ventilate and if really too high you will overheat. But I've got mine up in the top hole and only see a little venting in turns (I have to learn to trim in) or when taking off without trimming properly. If I use my trim right, I don't vent at all. And I've run 20 minutes at WOT with no overheating. My plate is a good 2 inches above the bottom of my boat. I've got a 1980 115 on an 18' Starcraft aluminum. With a 15p prop, I get ~5,800 rpm and almost 40 mph.

 

[dieselcat]

Re: 1987 erude 88 SPL

All i know is the only info i can give is what i have given.Brand new tach,i know that doesn't mean it's right but i got accurate reading with it on the merc.And i'm pretty sure the gps doesn't lie.And the # i gave for the prop is stamped into the prop,could be a miss stamped prop.Who knows?Is there a way to check the pitch of a prop other than info i have given.

 

[dieselcat]

Re: 1987 erude 88 SPL

First, I was going to post what hwsii did. Something is wrong with your number. Whether your tach is off or you have the prop pitch wrong, something is wrong.

As for raising the motor, if you go too high your prop will ventilate and if really too high you will overheat. But I've got mine up in the top hole and only see a little venting in turns (I have to learn to trim in) or when taking off without trimming properly. If I use my trim right, I don't vent at all. And I've run 20 minutes at WOT with no overheating. My plate is a good 2 inches above the bottom of my boat. I've got a 1980 115 on an 18' Starcraft aluminum. With a 15p prop, I get ~5,800 rpm and almost 40 mph.

Something doesn't sound right with what you are saying bout your setup.I don't know where the plate is on my dads boat?But he has a 1998 alumacraft bass boat with a 98 120 erude vro.He's got a 21P Michigan Wheel Ballistic prop and at either 5800 or 6200 rpm [can't remember which he said] he gets 62 mph measured by gps,he leaves shoal runners set.I'm no expert by any means just letting you know what my dads boat runs and it sounds like your would be comparable?

 

[Silvertip]

Re: 1987 erude 88 SPL

If the AV plate is flush or below the bottom of the boat you could (and should) raise the engine at least two holes. I would bet this will raise rpm and speed. You can go as high as ventilation and water pressure allow. Prop design will determine how high that is. Your tach sould be set on 6P.

 

[dieselcat]

Re: 1987 erude 88 SPL

If the AV plate is flush or below the bottom of the boat you could (and should) raise the engine at least two holes. I would bet this will raise rpm and speed. You can go as high as ventilation and water pressure allow. Prop design will determine how high that is. Your tach sould be set on 6P.

So if i raise the motor up a little I could gain some rpm's?how will i know if i am getting enough water pressure?Should i install a water pressure gauge?

 

[Silvertip]

Re: 1987 erude 88 SPL

Anytime you are attempting to optimize a setup, especially when raising the engine, it is a good idea to install a water pressure gauge. In my view this is a "must have" gauge anyway. The tell tale merely tells you the water pump is working as would a water pressure gauge. However, when installing a WP gauge you also install a new impeller. You note pressure at idle and wide open throttle. In the future any deviation from those numbers indicates its time to look at the impeller. For engine height optimization it is again, essential as it tells you immediately if the engine is too high.

Yes - raising the engine will gain RPM. How much depends on the prop and the hull. Some props will run at higher settings than others. On real wide boats short turns at WOT will likely cause venting so you need to trim down in those turns. The main reason you gain rpm is because the less lower unit there is in the water the less drag there is.

 

[dieselcat]

Re: 1987 erude 88 SPL

Anytime you are attempting to optimize a setup, especially when raising the engine, it is a good idea to install a water pressure gauge. In my view this is a "must have" gauge anyway. The tell tale merely tells you the water pump is working as would a water pressure gauge. However, when installing a WP gauge you also install a new impeller. You note pressure at idle and wide open throttle. In the future any deviation from those numbers indicates its time to look at the impeller. For engine height optimization it is again, essential as it tells you immediately if the engine is too high.

Yes - raising the engine will gain RPM. How much depends on the prop and the hull. Some props will run at higher settings than others. On real wide boats short turns at WOT will likely cause venting so you need to trim down in those turns. The main reason you gain rpm is because the less lower unit there is in the water the less drag there is.

Why install new impellar when installing wpg?Does it come with special impellar,I just put a new impellar in it less than 2 months ago.

 

[Tacklewasher]

Re: 1987 erude 88 SPL

Something doesn't sound right with what you are saying bout your setup.I don't know where the plate is on my dads boat?But he has a 1998 alumacraft bass boat with a 98 120 erude vro.He's got a 21P Michigan Wheel Ballistic prop and at either 5800 or 6200 rpm [can't remember which he said] he gets 62 mph measured by gps,he leaves shoal runners set.I'm no expert by any means just letting you know what my dads boat runs and it sounds like your would be comparable?

Not really comparable. My 115 is a 1980 model where HP is measured at the crank. The 98 120HP is measured at the prop. Mine is about equivalent to a 90hp compared to newer motors. And a bass boat boat will run better than my semi-v hull.

Mine is running about as well as can be expected.

 

[Randybeall]

Re: 1987 erude 88 SPL

Why install new impellar when installing wpg?Does it come with special impellar,I just put a new impellar in it less than 2 months ago.

New impeller instlation is to give you the base line of what the best normal water pressure is. In the future if it drops off you will have warning that the impeller is damaged and needs replacement.
I am with the 'raise the engine group'. It can make a significant difference in performance, less drag and better driving in some boats as well.
Glad your getting it going and working on better performance.